| | The core of successful garden plant cutting propagation and seedling raising is that plant cells have omnipotent functions and plants have regeneration functions, which are the theoretical basis of cutting seedling raising. In this understanding, we should pay attention to the understanding of the biological characteristics of various garden plants, master the rooting ability of various cutting objects and the length of time required for rooting to choose different propagation and seedling raising methods; we should pay attention to the selection of cuttings, master the appropriate cutting period, and use artificial synthetic growth hormones and other measures to promote rooting of cuttings; pay attention to the influence of external environmental conditions on the rooting of cuttings, and use cutting technology that combines advanced science and technology with traditional technology to coordinate light, water, temperature, and substrate factors; pay attention to management; to promote the rooting of cuttings and improve the survival rate of cutting seedling raising. The level of gardening and greening work reflects the comprehensive level of economic and social development of a country or region. It has become an important part of building modern and garden-like cities and towns. The important indicators for evaluating the level of gardening and greening in a country are forest coverage and per capita green area. Since liberation, a lot of work has been done in greening construction and remarkable achievements have been made. However, compared with the greening work in some countries and regions, the greening coverage rate and per capita green area are still very low, and the grade of gardening and greening plants is not high. There are many reasons for this situation, and the long-term shortage of garden plants and monotonous varieties are one of the important reasons. Garden plants are the material basis of garden greening construction. Therefore, the combination of advanced science and technology with traditional technology to cultivate more garden plants in a shorter time and at a lower cost is a prerequisite for good garden greening. In addition to sexual reproduction, garden plants can also be obtained by asexual reproduction such as cuttings, layering, grafting, division, etc. using some of the vegetative organs of garden plants. Cutting propagation is the most widely used asexual propagation method. It can economically use propagation materials to raise a large number of seedlings and multi-season seedlings, and can maintain the characteristics of the mother plant. It is a practical propagation method especially for garden plants that do not bear fruit or bear little fruit. However, because the cuttings are separated from the mother plant, it is necessary to create suitable environmental conditions, have certain technical measures, and give careful and meticulous management in order to have rooting and survival. 1. The mechanism of rooting of garden plants by cuttings Cutting propagation is a method of propagation in which the plant's nutritional organs, roots, stems, and leaves are inserted into soil, sand or other matrices under certain conditions, so that these nutritional organs can grow other missing parts away from the mother body and become a complete new plant. There are many types of cutting propagation, such as branch cutting, root cutting, leaf cutting, etc. In the practice of seedling production, branch cutting is the most widely used. The following mainly introduces branch cutting: 1.1 Cutting rooting mechanism The reason why the vegetative organs of many garden plants can grow missing parts and form new plants when they are separated from the mother body is that, first of all, they rely on the omnipotence of plant cells. The existence of plant cell DNA in the form of chromosomes and other mechanisms prevents most genetic information from being expressed. The interaction between various regulatory sites of genes and proteins such as specific transcription factors ensures the spatiotemporal specific expression of plant genes. Plant cells perform specific functions of their tissues on the whole plant. In vitro tissues or cells can dedifferentiate and regenerate complete plants under appropriate conditions, which means that each cell has the potential to form the entire plant body; secondly, they also rely on the regeneration function of the plant body, that is, when a part of the plant body is injured or removed and the whole plant is damaged, it can show the function of compensating for damage and restoring coordination. Therefore, when the cuttings are separated from the mother body, due to the omnipotence and regeneration function of the plant, the cambium, secondary phloem, vascular fibers and pith in the cuttings can form the original body of adventitious roots and then develop and grow into adventitious roots to form a complete plant. 1.2 Types of rooting of cuttings The key to the survival of cuttings is root formation. There are the following rooting types according to the location of adventitious roots: First, rooting in the skin Many special thin-walled cell groups can form in the cambium of the cuttings to become root primordia, which are the material basis for the production of adventitious roots. Root primordia are mostly located at the intersection of the widest part of the medullary ray and the cambium, and are formed by cell division in the cambium. Due to cell division, they differentiate outward into blunt-conical root primordia, invade the phloem and pass through the lenticels. During the outward development of the root primordia, the medullary rays connected to it gradually thicken, pass through the wood to the medulla, and obtain nutrients from the medullary cells. When the cuttings have formed root primordia, adventitious roots can grow from the lenticels in a short time under suitable temperature and humidity conditions. This kind of cortical rooting is relatively rapid, so all tree species that are easy to survive and root quickly, such as willows, coral trees, banyan trees, and many herbaceous flowers such as marigolds and saffron, mostly root from the cortex. Second, healing tissue takes root Any plant has the ability to recover after partial injury, protect the wound and form healing tissue. The selected cuttings should also produce new protrusions at the lower incision, which is the healing tissue. The living cells of the cambium, pith and pith rays of the plant body are the main parts of the healing tissue. At the cutting incision, because the cambium cells and cells near the cambium have the strongest ability to divide, translucent thin-walled cells with obvious nuclei are formed on the surface of the lower incision to form the primary healing tissue. On the one hand, it protects the cutting incision from the adverse external environment, and at the same time, it has the ability to continue to divide. Its cells continue to differentiate and gradually form tissues such as xylem, phloem and cambium that are connected to the corresponding tissues of the cuttings, and finally fully heal. These healing tissue cells and cells near the healing tissue continue to differentiate to form root growth points. Under suitable temperature and humidity conditions, a large number of adventitious roots can be produced. Since this kind of rooting requires the growth of healing tissue and then differentiation and rooting, it takes a long time and the rooting is slow. Therefore, the rooting parts of tree species that take a long time to root and are difficult to survive, such as osmanthus, camellia, etc., are mostly healing tissue rooting. It is not difficult to see that the totipotency of plant cells and the regeneration function of plants are the theoretical basis of cutting propagation. Therefore, we can adopt the seedling raising method of cutting propagation for many garden plants. However, due to biological differences, the ease and difficulty of rooting of various plants vary. This requires that in the process of cutting propagation, we should master the biological characteristics of various garden plants, analyze the various factors affecting rooting and survival, and take corresponding measures to promote rooting of cuttings on this basis. 2. Internal factors affecting rooting of cuttings Whether the plant cuttings can take root and how fast they can take root has a lot to do with the plant itself and the conditions of the cuttings. 2.1 Garden plants are restricted by their own genetic characteristics and have different rooting abilities The growth activities of plants are controlled by special growth substances, and the rooting of plant cuttings and the formation of healing tissues are all life activities of plants, which are all controlled and regulated by auxins. Some plants contain more auxins, and wounds on branches and trunks can heal quickly. These plants are easy to root after cutting. Therefore, there is a saying that "flowers planted intentionally will not grow, but willows planted unintentionally will grow into shade." Willows have strong ability to produce healing tissues and rooting, which means that they contain more auxins, while other plants contain less auxins, most of them grow slowly, and wounds are not easy to heal. It is difficult for these plants to root after cutting. This is the case with conifers. Therefore, according to the amount of auxins contained in garden plants and the strength of their rooting ability, they can be divided into: Easy-to-root types: Cuttings take root easily and quickly, such as poplar, willow, red birch, sycamore, banyan, chrysanthemum, petunia, marigold, and verbena. Types that are more difficult to root: The cuttings can take root, but the rooting process is slow, such as camellia, osmanthus, cedar, Michelia, maple, Podocarpus, etc. Extremely difficult to root: The cuttings cannot take root or have difficulty taking root, such as pine, camphor, cockscomb, canna, etc. In production practice, different propagation methods and measures should be adopted according to the differences in the rooting ability of garden plants. For plants that are extremely difficult to root, cutting propagation and seedling raising should not be adopted. For plants that are easy to root, simpler measures and general management methods can be adopted. For plants that are difficult to root, sophisticated management methods should be adopted, using more advanced full-sun intermittent spray cutting method and closed cutting method and other technologies. Various artificially synthesized auxins can also be used to treat the cuttings to promote rooting. | 2.2 The age of the mother plant, the age of the branches and the location of the cuttings are also internal factors that affect the rooting of the cuttings. The rooting ability of cuttings often decreases with the increase of the age of the mother plant. The older the mother plant is, the older its stage of development is, the vitality declines, the growth hormone decreases, and the cell fertility decreases. On the contrary, young mother plants have a shorter stage of development, rich nutrition, more hormones, and strong cell division ability, which is conducive to rooting. Therefore, branches taken from young mother plants are easy to root. In the comparative test of Pittosporum cuttings, one-year-old cuttings were taken from mother plants of different ages, and the rooting survival rate of cuttings was quite different in the same environment. Similarly, the age and attachment position of the mother branch are also factors that restrict the rooting ability of the cuttings. In addition, the quality and fullness of the development of the cuttings will affect the amount of nutrients in the cuttings, and also have a certain impact on the rooting of the cuttings. The nutrients accumulated in the cuttings are the main source of nutrients needed for the formation of new organs and initial growth after cuttings. In particular, the amount of carbohydrates is closely related to rooting and survival. Practice has shown that cuttings that are well developed and rich in nutrients are easy to survive. In production practice, the "heel-shaped cutting method" is often used to allow the cuttings to carry two-year-old branches so that the cuttings have more nutrients, which is conducive to the rooting of the cuttings. The "heel-shaped cutting method" was used for cuttings of azalea and Michelia, and achieved better cutting seedling results. Heel-shaped cuttings are when cutting cuttings, you can bring a few branches from the previous year to the base of the cuttings, which will make it easier to root. Heel-shaped cuttings are when the base of the cuttings is equipped with some 2-year-old semi-lignified branches, which are like heels and feet. The nutrients in the lower part of this cutting are concentrated, making it easy to root. It is suitable for tree species that are difficult to survive, such as osmanthus. When cutting cuttings, select 1-2-year-old semi-lignified branches with branches and cut them from about 1 cm below the branch, then break off the branches by hand, cut off the leaves at the base, and leave only 2-3 leaves at the top. The semi-lignified branches at the base are used as cuttings. You can also prune the mother plant in spring and summer to promote branching, and cut cuttings in the second year. If the cuttings are long, the semi-lignified branches cut from the upper part can also be used as conventional cutting cuttings. If the base of the broken cuttings has too much outer skin, you can appropriately cut off part of the excessively long epidermis. In a word, in the process of cutting seedling raising, we should pay attention to the selection of cuttings, and the general direction is: young mother plants are better than old mother plants; one-year-old branches are better than two- and three-year-old branches; base sucker branches are better than upper crown branches; middle branches are better than top branches; sunny branches are better than shady branches; side branches are better than top branches. This is because young mother plants, one-year-old branches, sunny branches, side branches, sucker branches, and middle branches contain more nutrients, have rich tissues, strong regeneration ability, and have strong rooting ability. Therefore, the correct selection of cuttings is a necessary measure to improve the rooting and survival of cuttings. 3. Environmental requirements for rooting and survival of cuttings The growth of plants is the result of the coordination of various physiological activities in the body. These physiological activities include photosynthesis, respiration, water absorption and transpiration, mineral absorption, transformation and transportation of organic matter, etc. Therefore, any external conditions that can affect these physiological activities can affect the growth or rooting of plants, mainly including light, temperature, water, etc. Cutting propagation is a method of propagating cuttings without roots. Therefore, the requirements for external environmental factors are more stringent. Whether it is possible to artificially create the environmental conditions such as temperature, water, light, substrate, etc. required for the rooting and growth of cuttings becomes the key to the success of cutting seedling cultivation. 3.1 Temperature requirements Temperature affects the rooting of cuttings from two aspects: air temperature (air temperature) and substrate temperature. 3.1.1 Requirements for temperature Temperature has a great influence on the rooting of cuttings. If the temperature is suitable, the rooting will be fast, and vice versa, the cuttings may even die. Plants have a certain temperature range for growth, and different plants grow or take root at different temperatures, which is related to the climatic conditions of their origin. Plants originating from tropical areas have higher growth and rooting temperatures; plants originating from temperate areas have lower growth and rooting temperatures. The suitable temperature for most garden plants to take root is 15-25℃, such as azaleas and camellias. Plant species originating from tropical areas require a suitable temperature above 25℃, such as jasmine, Milan, rubber trees, dragon blood trees, and hibiscus. However, snapdragons, fuchsias, and calendulas can also take root at lower temperatures of around 10℃. Therefore, when propagating by cuttings, the biological characteristics of various plants should be mastered, and cuttings under the most suitable temperature conditions will promote early rooting of cuttings. 3.1.2 Requirements for substrate temperature Generally speaking, if the temperature of the cutting medium is 3-5℃ higher than the air temperature, it is conducive to the rooting of the cuttings. Because when the air temperature is higher than the temperature of the medium, it is easy to cause the water and nutrients stored in the cuttings to be transported to the upper end of the cuttings. The cuttings will first sprout and leaf, but cannot take root. Once the new leaves consume the water and nutrients stored in the cuttings, they will die. This phenomenon is called the "false living phenomenon" of the cuttings. On the contrary, when the air temperature is 3-5℃ lower than the temperature of the medium, it will cause the water and nutrients stored in the cuttings to be transported to the lower end of the cuttings. The rooting growth rate of the cuttings underground is faster than that of the above-ground part. It is conducive to the survival of the cuttings to make the cuttings take root first and then sprout branches and leaves. Therefore, in order to prevent the "false living phenomenon" of the cuttings in production practice, we can lay electric heating wires at the bottom of the medium for heating or place the cutting container near the heating equipment to increase the temperature of the medium. When the air temperature is high, we can also use shading, water spraying and other methods to reduce the temperature so that the temperature of the medium is higher than or close to the air temperature, creating a suitable temperature for rooting. 3.2 Requirements for moisture The normal growth process of plants must be in a saturated state with water content in the cell protoplasm. Water is needed for cell division, expansion and elongation. Water is also an important raw material for some metabolic processes. Photosynthesis, respiration, and the synthesis and decomposition of organic matter also require water. When water is lacking, the degree of dispersion of protoplasm colloids decreases, changing from sol to gel, metabolic activity weakens, photosynthesis is blocked, hydrolysis and respiration are strengthened, and the synthesis of organic nutrients and auxins is reduced, resulting in inhibition of normal plant growth and rooting. Before rooting, it is difficult for cuttings to absorb water from the substrate. In addition, due to transpiration, especially for cuttings with leaves, it is very easy for cuttings to lose water. Therefore, it is extremely important to maintain the air humidity and a certain substrate humidity so that the cuttings do not lose water and maintain their vitality. The requirements of cuttings for water are specifically reflected in two aspects: air humidity and substrate humidity. The closer the air humidity is to saturation, the more beneficial it is for the healing of cuttings. The thin-walled cells in the callus are tender and weak, not resistant to dryness, and the cells are prone to water loss when the humidity is lower than the saturation point, which can easily cause death over time. Full cells are more conducive to the proliferation of callus than cells with insufficient water content. Therefore, maintaining a high saturated air humidity of 80-90% to reduce the water loss of cuttings to the lowest point is extremely beneficial to the rooting of cuttings. At the same time, the humidity of the cutting substrate should be appropriate, which not only ensures the humidity required for the rooting of cuttings, but also does not cause the substrate temperature to drop due to excessive water, prolong the rooting time, and even cause poor substrate ventilation. Low oxygen content causes the cuttings to suffocate and rot due to lack of oxygen. Generally, the water content of the substrate should be 50-60% of the maximum water holding capacity. Therefore, in production practice, it is best not to water the substrate continuously for fear of water loss in the cuttings, which will cause the cutting to fail due to excessive substrate humidity. The closed cutting method using plastic arch shed and sunshade net is adopted. The film seals the cutting bed to keep moisture, improves the air humidity, and reduces the number of times the substrate is replenished. At the same time, the temperature is adjusted by combining shading facilities, which better coordinates the relationship between air humidity, substrate humidity and temperature. 3.3 Requirements for lighting Light is a necessary element for the normal growth of green plants. The effect of light on the rooting of cuttings is: on the one hand, appropriate light can increase the temperature of the substrate and air, and enable the cuttings to accumulate nutrients through photosynthesis to promote the formation of growth hormones and promote the rooting of the cuttings; on the other hand, light will make the temperature of the cuttings too high, and the transpiration of water will be accelerated, resulting in water loss and drying or burning of the cuttings. Therefore, the cuttings are required to be inserted in a place where they can see the sky but not the sun, avoiding direct exposure to strong light. In the early stage of cutting, especially when the cuttings have not taken root, shade should be provided to reduce the temperature, and water spraying should be used to reduce the temperature and increase the humidity, reduce water loss, and eliminate the adverse effects of light on the rooting of the cuttings. However, as the root system grows, the time the cuttings are exposed to light should be gradually extended. 3.4 Requirements for the matrix Practice has proved that the occurrence and development of root primordia require the participation of a large number of oxygen molecules. Therefore, the use of a cutting medium with good air permeability to promote the occurrence and development of root primordia is conducive to the rooting of cuttings. However, the moisture and oxygen in the matrix are often contradictory. Sufficient oxygen in the matrix often leads to a decrease in moisture, which can easily cause water loss in the cuttings. Excessive moisture in the matrix can easily cause poor ventilation. The obstruction of gas exchange causes the cuttings to be in an anaerobic respiration state for a long time, which is easy to produce alcohol and lactic acid, affecting rooting and even rotting. Therefore, in order to coordinate this contradiction, the materials used in the cutting matrix should have the characteristics of heat preservation, moisture retention, looseness and breathability, and no bacteria. In production, rice husk ash, perlite, vermiculite, peat soil, coal slag, sand, etc. are often used as cutting matrices. These materials can be used alone or mixed with each other. When cutting on a large area, some matrix materials can be mixed with well-drained sandy loam. In recent years, yellow sand, coal slag, rice husk ash, sawdust and other materials are mixed with sandy loam as cutting medium to make the medium meet the requirements of looseness, air permeability and moisture retention. In addition, the medium should be disinfected with drugs before cutting. You can use 50% mancozeb 1:200-400 times liquid, 2-4 kg per square meter or 1:200-300 times potassium permanganate, about 0.5 kg of water per square meter, spray the cutting medium, and then cover it with a film for 3 days to kill the bacteria, and then uncover the film for 2-3 days to volatilize the drug. 3.5 Coordination requirements for various external environmental factors The influence of external environmental factors such as light, water, temperature, and substrate on the rooting of cuttings is actually comprehensive. Therefore, in the process of cutting seedlings, we should not overemphasize certain factors and ignore other environmental conditions, such as emphasizing light intensity and ignoring water, paying attention to water but not considering the air permeability of the substrate, etc. These will affect the rooting of cuttings. "Full-light intermittent spray cutting bed" is used for cutting seedlings. That is, using sufficient sunlight during the day for cuttings, which is conducive to the photosynthesis of cuttings, thereby accumulating nutrient hormones to promote rooting. The automatic control of intermittent spraying is used to meet the requirements of cuttings for temperature and air humidity, ensuring that the cuttings do not wilt, and using vermiculite, yellow sand and other materials with good air permeability as cutting substrates, which better coordinates the influence of environmental factors such as substrate, temperature, humidity, and light on cuttings, greatly improving the survival rate of cuttings. According to the requirements of cuttings for various environmental conditions, a closed cutting method with plastic arch shed and multi-layer sunshade net is used. For some plants that are difficult to root, such as azalea, Podocarpus, camellia, cedar, and precious roses, the specific method is: First, use bamboo blocks to make the first layer of skeleton arch on the cutting bed, which is used to cover the plastic film. The main functions are to keep warm, moisturize, and transmit light, increase the air humidity in the bed, reduce the number of watering, prevent heavy rain from causing the cutting bed substrate to become hardened, increase its air permeability, and better coordinate the relationship between substrate humidity and air humidity. Second, use a longer bamboo block to make a second layer of skeleton arch on top of the first layer of skeleton arch. The space between the two skeleton arches should be 20-30cm. Cover the upper layer of skeleton with a sunshade net, which is mainly used to block direct strong light and reduce the temperature of the cutting bed in the plastic arch shed. Depending on the weather conditions and the increase in the growth time of the cuttings in the cutting bed, the covering time of the sunshade net can be flexibly controlled. The application method of using the lower layer as a plastic shed and the upper layer as a sunshade net can effectively promote the photosynthesis of the cuttings, which is conducive to the formation and accumulation of nutrients and hormones, and can also avoid burns and other injuries to the cuttings caused by strong light and high temperature. It better coordinates the requirements of the cuttings for light, temperature and humidity. Third, the rooting period of many garden plants that are difficult to root must go through the hot July and August. In order to avoid the damage of high temperature and strong light to the cuttings, a high-rise sunshade can be built on the basis of the double-frame shed. The sunshade nets around the shed should not be hung too much, and should be at a distance from the ground. This can not only reduce the direct strong light at noon, but also allow the side scattered light in the morning and afternoon to penetrate into the cutting bed, so that the humidity in the first layer of the plastic shed is maintained at a high level without causing the temperature to be too high, which is also conducive to photosynthesis and promotes the rooting and growth of the cuttings. Five internal factors that affect the rooting of cuttings
1. Biological characteristics of tree species
Different tree species have different biological characteristics, so their branch rooting ability is also different. Trees can be divided into four types according to the difficulty of rooting cuttings.
(1) Tree species that are easy to root include willow, poplar, black poplar, metasequoia, pond cypress, fir, cryptomeria, amorpha, forsythia, boxwood, rose, winter jasmine, ivy, nandina domestica, fig, pomegranate, erythrina, etc.
(2) Tree species that are relatively easy to root include arborvitae, cypress, cypress, podocarpus, locust, locust, tea, camellia, cherry, wild rose, azalea, pearl bush, oleander, citrus, privet, acanthopanax, elderberry, etc. (3) Tree
species that are relatively difficult to root include golden pine, juniper, cypress, Japanese five-needle pine, cedar, Milan, begonia, jujube, sycamore, chinaberry, ailanthus, etc.
(4) Tree species that are extremely difficult to root, such as black pine, masson pine, camphor, chestnut, walnut, oak, tulip tree, persimmon, Araucaria, etc.
The difficulty of rooting different tree species is only relative. With the continuous deepening of scientific research, tree species that are difficult to root can also achieve a higher survival rate and be promoted and applied in production.
2. The age of the mother tree and the cuttings
The age of the mother tree and the age of the branches (cuttings) themselves have a significant impact on the survival of cuttings. This impact is greater for tree species that are difficult to root and difficult to root.
(1) The age of the mother tree The older mother trees develop slowly and have low cell division ability. In addition, as the age of the tree increases, the hormones and nutrients contained in the branches change, especially the content of inhibitory substances increases with the age of the tree, causing the rooting ability of the cuttings to decrease with the age of the mother tree and the growth is also weak. Therefore, when selecting cuttings, they should be taken from young mother trees, and it is best to use branches from 1-2 year old seedlings. For example, the Hubei Qianjiang Forestry Research Institute conducted a cutting experiment on Metasequoia, and found that the rooting rate of cuttings collected from one-year-old mother trees was 92%, 66% from two-year-old mother trees, 61% from three-year-old mother trees, 42% from four-year-old mother trees, and 34% from five-year-old mother trees. As the mother tree age increases, the rooting rate of cuttings decreases.
(2) Cutting age The rooting ability of cuttings also decreases with the increase of their own age. Generally, one-year-old branches have the strongest regeneration ability, but the specific age also varies from tree species to tree species. For example, the survival rate of one-year-old branches of poplars is high, while the survival rate of two-year-old branches is low. Even if they survive, the growth of seedlings is poor. One-year-old branches of Metasequoia and Cryptomeria are better, and a small section of two-year-old branches can be added at the base; while the rooting rate of Podocarpus is high with 2- to 3-year-old branches. Generally speaking, the survival rate of slow-growing tree species with a part of 2-3-year-old branches is higher. The survival rate of tree species that are difficult to root and difficult to root is higher with half-year-old or younger branches.
In addition, the thickness of branches is different, and the amount of stored nutrients is different. Thick cuttings contain more nutrients, which is beneficial to rooting. Therefore, the branches of hardwood cuttings must be fully developed, thick, fully lignified, and free of diseases and insect pests. The appropriate thickness of cuttings varies depending on the tree species. Most coniferous tree species are 0.3-1cm, and broad-leaved tree species are 0.5-2cm.
3. The rooting rate of branches
on the crown is low, while the root and stem base sprout branches have a high rooting rate. Because the one-year-old sprouts at the root neck of the mother tree are the youngest in the development stage and have strong regeneration ability, and because the growth position of the sprouts is close to the root system, they get more nutrients and have higher plasticity, which makes them easy to survive after cutting. Although the rooting rate of the branches sprouting from the trunk base is high, the source is limited. Therefore, it is ideal to collect cuttings from a scion nursery. If there is no scion nursery, cuttings, rooted seedlings and stems of rooted seedlings can be used.
In addition, the branches on the main trunk of the mother tree have strong rooting ability, while the side branches, especially the side branches with multiple branches, have weak rooting ability. If cuttings are taken from the crown, it is better to take cuttings from the lower part of the crown where the light is weaker. In production practice, some tree species have a part of 2-year-old branches. The "heel cutting method" or "horseshoe cutting method" can improve the survival rate.
The branches of hardwood cuttings must be well-developed, thick, fully lignified, and free of diseases and pests. Thick cuttings contain more nutrients, which is beneficial to rooting. The suitable thickness of cuttings varies according to the tree species. Most coniferous tree species are 0.3 to 1 cm, and broad-leaved tree species are 0.5 to 2 cm.
4. Different parts of branches
The number of root primordia and the amount of stored nutrients in different parts of the same branch are different, and the rooting rate, survival rate and seedling growth of the cuttings are significantly different. Generally speaking, the middle and upper branches of evergreen species are better. This is mainly because the middle and upper branches grow robustly, have vigorous metabolism, sufficient nutrition, and the photosynthesis of the new branches in the middle and upper parts is also strong, which is beneficial to rooting. The middle and lower branches of deciduous tree species are better for hard branch cuttings. Because the middle and lower branches are well developed and store more nutrients, they provide favorable factors for rooting. If the tender branches of deciduous tree species are cut, the middle and upper branches are better. Because the middle and upper parts of the young branches have the highest content of auxin and strong cell division ability, it is beneficial to rooting. For example, the tip cuttings of Populus tomentosa are the best.
5. The number of leaves and buds on the cuttings
The buds on the cuttings are the basis for the formation of stems and trunks. Buds and leaves can provide the nutrients, growth hormones, vitamins, etc. necessary for the rooting of the cuttings, which is beneficial to rooting. Buds and leaves are more important for softwood cuttings and cuttings of coniferous and evergreen species. The number of leaves left on the cuttings generally depends on the specific situation, ranging from 1 to hundreds of leaves. If there is a spray device, spray moisture at any time, then more leaves can be left.
Four external factors affecting the rooting of cuttings
The external factors affecting the rooting of cuttings include temperature, humidity, light and substrate aeration. The various factors affect and restrict each other. These environmental conditions must be met to improve the survival rate of cuttings.
1. Temperature
The suitable temperature for rooting cuttings varies from tree species to tree species. The optimum temperature for rooting of most tree species is 15-25℃, with 20℃ being the most suitable. Plants in different climatic zones have different optimum temperatures for cuttings. Molisch.H of the United States believes that temperate plants are suitable at around 20℃, and tropical plants are suitable at around 23℃. Scholars from the former Soviet Union believe that temperate plants are 20-25℃; tropical plants are between 25 and 30℃.
The appropriate temperature difference between soil temperature and air temperature is conducive to rooting of cuttings. Generally, soil temperature is 3-5℃ higher than air temperature, which is extremely beneficial to rooting. In production, materials such as horse manure or electric heating wires can be used to increase ground temperature. The heat energy of sunlight can also be used to promote rooting and improve the survival rate of cuttings.
Temperature is more important for softwood cuttings. Temperatures below 30℃ are conducive to rooting inside the branches and promoting the utilization of substances, so it is beneficial to rooting. However, temperatures above 30℃ will lead to failure of cuttings. The incision can generally be sprayed or shaded to reduce the temperature. The best period for cuttings to move is also the period when corrupt bacteria are rampant, so special attention should be paid to taking anti-corrosion measures during cuttings.
2. Humidity
During the rooting process of cuttings, the relative humidity of the air, the humidity of the cutting soil, and the water content of the cuttings themselves are the key to the survival of cuttings, especially for softwood cuttings, and special attention should be paid to maintaining appropriate humidity.
(1) Relative humidity of the air The relative humidity of the air has a great impact on needle and broad-leaved tree species that are difficult to root. The relative humidity of the air required for cuttings is generally around 90%. For hardwood cuttings, it can be slightly lower, but for tenderwood cuttings, the relative humidity of the air must be controlled above 90% to minimize the transpiration intensity of the branches. In production, methods such as water spraying, interval controlled spraying, and film covering can be used to increase the relative humidity of the air so that the cuttings are easy to root.
(2) Humidity of the cutting soil Cuttings are most likely to lose water balance, so the cutting soil must have appropriate moisture. The humidity of the cutting soil depends on the cutting medium, cutting materials, and management technology level. According to the Populus tomentosa cutting experiment, the moisture content in the cutting soil is generally 20% to 25%. When the moisture content of the Populus tomentosa cutting soil is 23.1%, the survival rate is 34% higher than that of the cutting soil with a moisture content of 10.7%. When the moisture content is lower than 20%, both the rooting and survival of the cuttings are affected. It has been reported that the water content of the soil required for cuttings varies from cutting to callus production and rooting, with the former being higher and the latter two decreasing in turn. Especially after complete rooting, the water supply should be gradually reduced to inhibit the vigorous growth of the aboveground part of the cuttings, increase the degree of lignification of new branches, and better adapt to the field environment after transplantation. Excessive water often easily causes the lower incision to rot, leading to the failure of cuttings, which should be taken seriously.
3. Substrate
aeration conditions When cuttings take root, oxygen is required. A well-ventilated substrate can meet the oxygen needs of cuttings for rooting, which is conducive to rooting and survival. A substrate with poor aeration or too much water in the substrate and insufficient oxygen supply can easily cause the lower incision of the cuttings to rot, which is not conducive to rooting and survival. Therefore, the cutting substrate requires looseness and air permeability.
4. Light Light can promote the rooting of cuttings, which is indispensable for evergreen trees and tender cuttings. However, during the process of cutting, strong light will dry or burn the cuttings, reducing the survival rate. In actual production, measures such as spraying water or appropriate shading and film covering can be taken to maintain the water balance of the cuttings. In summer, the best method is to use full-light automatic intermittent spraying, which not only ensures water supply but also does not affect light.
Peeling, a method to promote rooting,
is for fruit trees with relatively developed branch cork tissue, and species and varieties that are difficult to root. Before cutting, the epidermal cork layer should be peeled off to promote rooting. After peeling, the water absorption capacity of the cuttings can be enhanced, and young roots are easy to grow.
1. Longitudinal incision
Use a knife to cut a 2-3 cm long wound to the phloem, and neatly arranged adventitious roots can be formed in the longitudinal incision groove. There is a circle of thick-walled fiber cells on the outside of the root progenitor site of the cortex of olive branches, which hinders the formation and outgrowth of the root progenitor. The longitudinal incision can injure this circle of thick-walled cell tissue, allowing the root progenitor to break through the barrier layer and grow adventitious roots.
2. Ring peeling:
The base of the branches prepared for cuttings on the mother plant is usually ring peeled 15 to 20 days before cutting. The cortex is ringed 3 to 5 mm wide. Cutting off the nutrient transport of the phloem allows the carbohydrates and auxin produced by the leaves to accumulate in the branches above the bark peeling part, forming good nutritional conditions, strengthening respiration, and increasing the activity of catalase, thereby promoting cell division and rhizogenes formation, which is beneficial to the promotion of adventitious roots. Other materials such as wire can also play the same role in twisting branches.
Yellowing treatment is a method to promote rooting
. Yellowed branches are easier to root than ordinary branches. For apple trees that are difficult to root, cover the branches with black paper bags before the leaves unfold in spring. The new shoots turn yellow in the paper bag and grow weakly. When 5 to 6 leaves unfold, the paper bag is removed, but the 3 to 6 cm part of the base of the branch is still wrapped with black cloth, not exposed to sunlight, and continues to turn yellow. The branches treated in this way are taken for cuttings in late August, and most apple varieties can take root. There are rhizogenes on the inner side of the axils of apple branches. After the branches become lignified, they can no longer develop into roots. Yellowing allows the branches to maintain the rooting function for a long time and maintain the state of meristem. As long as certain conditions are met at this time, roots will be generated. Yellowing treatment can also inhibit the formation of rooting-hindering substances, enhance the activity of plant growth hormones, and facilitate rooting. After the branches are yellowed, the tissue will not form an endothelial layer, and the degree of tissue hardening is reduced, so the induction of rhizogenes can occur from the yellowed parts. However, the main reason for the formation of morphological roots is the increase of endogenous IAA in the yellowed parts. The yellowed part of the apple branch is very different from the untreated part. The proportion of the green layer and pith of the cross-section of the yellowed branches increases, the mechanical tissue similar to the thick membrane tissue is underdeveloped, and the cell wall is also thinner. The starch content in the branch tissue increases, and the tannin content decreases. The activity of IAA in the ether extract of the yellowed part increases, while the inhibitory substances decrease.
At present, the yellowing treatment is generally carried out in the early growth stage of the new shoots, that is, three weeks before cuttings. Wrap the base with absorbent cotton first, and then wrap the base with black cloth, black nylon or black paper. For example, when cutting Fengmu, the branches can be pressed down and covered with soil to yellow. If the yellowed branches are treated with auxins such as IBA and then cut, the effect will be better.
Heating treatment method for early spring cuttings
Early spring cuttings often have difficulty taking root due to insufficient soil temperature. Therefore, when cutting grapes, most of them use fire pits to increase temperature to promote rooting of cuttings. A layer of sand or sawdust is spread on the kang surface, 3 to 5 cm thick, and the cuttings are buried upright in bundles. Wet sand or wet sawdust is inserted between bundles to expose the top buds. The base of the cuttings is kept at 20 to 28°C and the air temperature is below 8 to 10°C. To maintain humidity, water should be sprayed frequently to make the root protists divide rapidly, while the buds are delayed in germination due to the temperature limit. Now electric heating wires and thermostats are mostly used for control to keep the substrate soil temperature constant and promote rooting.
First, place the grape cuttings upside down in the ice-bottomed cold bed, bury them with sawdust, make the top of the cuttings close to the ice bottom, and keep them below 5°C; the lower end of the cuttings is upward, and horse manure is spread on the sawdust. Use water spray to adjust the temperature to keep it at 20-28°C. After more than 20 days of treatment, roots can be taken, and 5-7 days after planting, they can germinate.
Root-promoting treatment is carried out indoors. Wet sawdust and wet coconut shell powder are used together with the cuttings, and they are wrapped into small packages with plastic film. Every ten or so packages are put into plastic bags to promote rooting in a relatively stable environment of temperature, humidity and ventilation, and then moved into the nursery.
Plant endogenous auxin treatment method
Indoleacetic acid is very valuable for promoting adventitious roots in stems and leaves. Later, artificially synthesized auxins appeared one after another, including IBA, NAA, etc. People soon found that IBA and NAA were more effective than IAA in promoting rooting, especially IBA.
Different types of auxins have different stability. Unsterilized indoleacetic acid solution is quickly destroyed by bacteria. The concentration of 9 mg/kg disappears within 24 hours, and 100 mg/kg disappears within 14 days. In the sterilized solution, these substances can remain active for several months, but indolebutyric acid and acetic acid are very stable. Indoleacetic acid is sensitive to light. The solution with a concentration of 10 mg/kg is destroyed in 15 minutes under strong light, while indolebutyric acid only changes slightly after being exposed to strong light for 20 hours. Therefore, indoleacetic acid should be used immediately after preparation (Mes, 1951), otherwise it will deteriorate.
Although endogenous auxin in plants flows from the top to the base, in practice, base treatment is more effective. The respiration rate of cuttings treated with indolebutyric acid was 4 times that of untreated cuttings. In addition, the amino acid content at the base of cuttings treated with indolebutyric acid for 48 hours increased significantly, which obviously mobilized the upper substances and transported them down.
There are two methods of auxin treatment: dipping in dilute solution. For hard branches, the concentration is usually 5-100 mg/kg. The base of the cuttings is dipped for 12-24 hours. For tender branches, the concentration is usually 5-25 mg/kg. The dipping is done for 12-24 hours. In addition, the auxin is prepared into a high-concentration solution of 2,000-4,000 mg/kg for 5 seconds. The treatment time is short and it is more convenient. There are also 500-1,000 mg/kg concentrations, which are dipped for 1-2 hours. For example, this method is used in Fujian to treat litchi cuttings with IBA, and the rooting effect is very good.
Powder dipping: Use talcum powder as a diluted filler, prepare 500-2,000 mg/kg, mix for 2-3 hours and it can be used. First soak the base of the cuttings with clean water, then dip in powder for cuttings.
Chemical treatment method of cuttings
Some cuttings that are difficult to root can be treated with auxin first and then with vitamin B1 to obtain a higher rooting rate. Therefore, some people believe that auxin promotes root formation or can only form rhizogenes, while the role of vitamin Bl is to promote root elongation. In lemon cuttings, in addition to plant hormones, adding a small amount of vitamin Bl can promote rooting. Vitamin C also promotes rooting in cuttings. Lemon is easier to root than other citrus species, which is related to the high vitamin C content in the plant itself. Vitamin H is an essential biotin for rooting. The role of vitamin Bl is similar to that of vitamin H, so vitamin Bl is actually used more. The vitamin treatment concentration is 1 mg/kg, and the base of the cuttings is immersed for about 12 hours. Sugars have a good effect on conifers such as yew and Japanese hemlock, camellia, boxwood, and other broad-leaved trees. Herbaceous chrysanthemums, pine needles and other horticultural ornamental plants also have a good effect on sugar treatment. Sugars are preferably sucrose 2% to 10% aqueous solution. Regardless of whether it is used alone or mixed with auxins, the base of the cuttings is generally immersed for 10 to 24 hours. The treatment time can be shorter at high temperatures and high concentrations. Treatment with potassium permanganate can promote rooting of Ligustrum lucidum, Cryptomeria fortunei, Banyan tree, Poinsettia, Chrysanthemum, and Perilla frutescens. The general treatment concentration is 0.1% to 0.5%, and the water is soaked for several hours to a day and night. In addition to activating cells, enhancing the respiration of the base of the cuttings, and converting the nutrients inside the cuttings into a usable state, potassium permanganate also has the functions of disinfection and sterilization, inhibiting the reproduction of undesirable microorganisms, and promoting rooting.
Treatment with silver nitrate may damage the base of the cuttings, but it has a certain effect on bayberry and chestnut, which have a high content of root-blocking substances and cause poor rooting.
Plant cutting propagation in different periods of spring, summer, autumn and winter
Plant cutting propagation can be carried out all year round if conditions permit, but it varies depending on the regional climate, plant characteristics and cutting methods.
1. Spring cuttings
are suitable for most plants, and deciduous tree species are mostly carried out in this season. Spring cuttings are done directly from dormant branches of the previous year or after low-temperature storage in winter. At this time, the cuttings are rich in nutrients and some rooting inhibitors have been converted. In order to prevent the uncoordinated development of the above-ground and underground parts from causing nutrient consumption and metabolic imbalance, spring cuttings should be done early, and conditions should be created to break the dormancy of the lower part of the cuttings and maintain the dormancy of the upper part. After the adventitious roots are formed, the buds will sprout and grow again, thereby improving the survival rate.
2. Summer cuttings
Summer cuttings are done by cuttings of young branches or semi-lignified cuttings that are growing vigorously in the current year. Cuttings of coniferous species are carried out at the top of the first growth and before the start of the second growth, using semi-lignified cuttings. Broad-leaved species use young branches in the vigorous growth period. Summer cuttings take advantage of the advantages of cuttings being in a vigorous growth period, strong cell division ability, vigorous metabolism, and high endogenous growth hormone content. These factors in the tree body indicate that they are conducive to rooting. However, the high temperature in summer can easily cause the death of young branches and leaves due to water loss. Therefore, measures should be taken to increase the relative humidity of the air, reduce the transpiration of the cuttings, maintain the balance of water metabolism in the body, and improve the survival rate of the cuttings.
3. Autumn cuttings
Autumn cuttings are carried out when the cuttings have stopped growing but have not yet entered the dormant period, when the leaves are nutrient-transfused and stored, and when the cuttings are rich in nutrients. At this time, cuttings are carried out to promote the early formation of callus tissue by taking advantage of the fact that the inhibitory substances in the cuttings have not yet reached their peak, so as to facilitate rooting. Second
, they take advantage of the climate change in autumn, that is, the ground temperature is later than the air temperature, which is conducive to the early formation of the root primordium of the cuttings. Autumn cuttings should be carried out early to facilitate complete material transformation, safe wintering, rapid rooting in the next spring, timely germination, and improve the survival rate of the cuttings. 4. Winter cuttings
Winter cuttings are cuttings made from dormant branches. The technical measures taken in different regions are different. In the north, winter cuttings are carried out in plastic sheds and greenhouses, and low-temperature treatment is required. Cuttings are carried out after breaking dormancy, and warming measures are taken in the soil to promote rooting and survival of the cuttings. In the south, cuttings can be directly taken from nurseries in winter. After the cuttings have been dormant in the nursery, when the temperature gradually rises, the cuttings begin to take root and sprout. The cuttings grow more vigorously and robustly than the surviving spring cuttings.
Four methods of selecting, cutting, cutting and storing hard branches
(1) Selecting and cutting cuttings Select branches of the same year (two-year-old branches can also be used if the source is scarce) or sprouting branches of a relatively young mother plant. The branches should be strong, free of pests and diseases, close to the main trunk, and lignified. Cutting cuttings should be taken when the tree stops growing or begins to shed its leaves. After cutting, cut the branches immediately into cuttings and then store them. You can also store them first and then cut the cuttings before cutting.
(2) Storage of branches Since cuttings are mostly taken in spring, branches need to be stored for a period of time after being cut. The most common storage method is to bury the cuttings in the open field. Choose a dry, well-drained, leeward and sunny place to dig a ditch, bundle the branches into bundles, bury them in the ditch, and cover them with wet sand and soil. If there are too many branches, you can put some grass bundles in the middle to facilitate ventilation. In the northern region, there are underground kilns for storage. It is safer to bury the branches in wet sand and stack them in 2 to 3 layers. Whether it is stored in the open field or indoors, it is necessary to check for mildew frequently to avoid affecting the survival rate. In the southern region, the method of cutting into cuttings first and then storing them is often used. This gives the cuttings enough time to heal the cut, promotes the transformation of rooting substances, and can facilitate storage and save land. The storage methods are roughly the same. For example, the cut cuttings need to be bundled according to a certain number (usually 50 to 100 branches per bundle), and the cuttings are placed vertically at the bottom of the ditch for better results.
(3) Cuttings The commonly used cutting method is to select the strong part of the middle section of the branch and cut branches about 10 to 20 cm long. Each cutting should retain 2 to 3 full buds, and the spacing should not be too long. The tip of the branch is generally not used. The cutting cut should be smooth, with the upper end about 0.5 to 1 cm above the bud and the lower end close to the bottom of the bud. The lower end of the cut is generally horizontal to ensure uniform rooting, but some tree species with slow rooting can also be cut into an inclined surface to expand the contact surface with the soil.
The upper end of the cut is generally inclined, with the bud side higher and the back bud side lower to avoid water accumulation after cutting. Thinner cuttings can also be cut into a flat surface.
(4) Cutting method When cutting, it can be straight or oblique, but the inclination should not be too large. The depth of the cutting into the soil is about 1/2 to 2/3 of its length. In arid areas and sandy soils, it can be appropriately deeper. Be careful not to damage the bud eye, do not shake it left and right when inserting it into the soil, and compact the surrounding soil with your hands. Due to the different characteristics of tree species and applications, many different methods of hard branch cuttings have been created in various places:
Long branch cuttings (long trunk cuttings): For some tree species that are easy to root, the cut branches can be inserted into the soil. This method can produce large seedlings in a short period of time and can also be directly inserted into green land to avoid transplanting procedures.
Cutting: For some tree species that are difficult to root, the lower end of the cuttings can be split and stones and other objects can be sandwiched in the middle to stimulate rooting.
Heel-shaped cuttings: A part of the old branch is attached to the lower end of the cutting, shaped like a heel, so it is called heel-shaped cuttings. In this way, the nutrients in the lower part are concentrated, making it easy to root, but each branch can only make one cutting, and the utilization rate is low.
Selection and cutting of soft branch cuttings
(1) Selection and cutting of cuttings Cuttings for soft branch cuttings should also be cut from young mother trees as much as possible, and strong, disease-free, pest-free, semi-lignified young branches of the current year should be selected. The best time to cut is at the end of the first growth period. Each cutting retains 3 to 4 buds. If the branches of the current year are short and can only be cut into one cutting, a part of the biennial tissue can be retained at the base to facilitate rooting. After the branches are cut, they should be kept fresh and cut into cuttings indoors. The cut should be made below the node as much as possible, and 1 to 2 leaves should be retained. For tree species with larger leaves, some leaves can be cut off, and tender shoots are generally removed to reduce evaporation. After the cuttings are cut, they should be propagated as soon as possible. If they cannot be propagated immediately, the lower end should be buried in wet sand indoors and watered frequently to keep them fresh. For soft-branch cuttings of evergreen coniferous tree species, it is generally sufficient to cut the lower cut flat, and there is no need to remove the leaves. However, if it is difficult to propagate into the soil, some of the lower branches and leaves can be appropriately removed.
(2) Method of propagation Because soft-branch cuttings have tender branches, the land for propagation needs to be more carefully organized and loose, so they are often carried out on the cutting bed. The cuttings are usually inserted vertically into the soil, with the part inserted into the soil being about 1/3 to 1/2 of the total length. Since soft-branch cuttings are often carried out during the rainy season or summer, attention should be paid to ventilation and shading, and high air humidity should be maintained to facilitate rooting. In the Jiangnan region, the high humidity during the rainy season from June to July is often used to carry out soft-branch cuttings of many tree species about half a month before the rainy season, so it is called "plum season cuttings".
(3) Single-bud branch cuttings Cuttings made from branches with only one bud (or a pair of buds) are called single-bud cuttings, also known as "single-bud cuttings". Single-bud cuttings save materials, the cuttings are very short, usually less than 10 cm, and the material utilization is economical, so it is gradually being promoted and applied. When cutting the cuttings, the incision is oblique and opposite to the bud. For tree species with opposite buds, the cuttings can be split in half, so that one can be used for two purposes. Since the cuttings are short and the incision is large, special attention should be paid to spraying water, shading, and wind protection after cutting to prevent the cuttings from losing water and affecting survival.
One of the characteristics of modern seedling raising technology is the selection of seedling pots
for container seedling raising. Container seedling raising is a modern seedling raising technology
. 1. Seedling pot (nutrient pot)
is a general term for pot-shaped seedling containers. Fertile nutrient soil or culture matrix is placed in the pot. According to the materials used to make the pot, it can be mainly divided into two categories: one is planted in the soil together with the seedlings, such as the honeycomb paper cups and fine felt paper nutrient cups in Finland, the United States, and Japan, the peat containers in Northern Europe, and the Walter bullet-shaped containers in Canada. These containers can be decomposed by water, plant roots, and microorganisms after being planted in the soil; the other is that the container needs to be removed when the seedlings are planted, such as the polystyrene (foam plastic) nutrient pots in Canada, the porous hard polystyrene nutrient cups in Sweden, and the thin plastic cups in Finland.
(1) Plastic cups are made of polystyrene, polyethylene, and polyvinyl chloride. They are generally 8 to 20 cm high and 5 to 12 cm in diameter. They have drainage and ventilation holes around them. This type of container is widely used at home and abroad. Bottomless plastic film pots (plastic film tubes) are also used for seedling raising.
(2) Peat pots are mostly made of peat and paper pulp. The water retention and air permeability of peat are beneficial to the breathing and growth of seedling roots. At the same time, after planting, the roots of seedlings can easily penetrate the container wall and take root in the soil. There are many shapes and sizes of peat containers, such as the Finnish square container Ep~615 and Ep~620. The former is 3cm×6cm in size, and 50 containers are pressed into a plate; the latter is 5cm×8cm in size, and 18 are pressed into a plate.
(3) Paper pots are made of paper pulp and hydrophilic synthetic fibers, a small amount of preservatives and fertilizers to form a hexagonal column with a diameter of 4cm×10cm and a height of 7.5~13cm. They are used to cultivate seedlings. If used for vegetables and flowers, smaller models can be used. Paper cups can be glued together with dissolving glue to form a honeycomb shape, so it is also called honeycomb paper cups in Japan. When not in use, it can be folded into a book. This container is easy to rot and will not hinder the growth of seedling roots.
Seedling soil block (nutrient brick) for seedling container Introduction:
The culture soil (nutrient soil) is pressed into shape and used for seedling cultivation. Because this soil block is prepared with sufficient nutrients required for crop growth, it is also called nutrient brick or nutrient soil block. This soil block is mostly cubic in shape with a small hole in the middle, which can be sown or transplanted. This nutrient soil block is mostly made by mechanization and is suitable for mechanized seedling cultivation and management. The amount of materials used in the preparation of soil blocks is large, so most of them are locally sourced, and there are large differences between different countries. The ingredients are mostly organic matter. For example, in the Netherlands, general vegetable seedling soil blocks are made of 80% peat, 10% clay and fine sand, and a small amount of fertilizer. Commonly used is 80% decomposed manure (or peat) and 20% soil. The soil requires loose sandy loam, and too much stickiness is not conducive to the growth of seedlings. The general requirements for soil blocks are moderate tightness, not hard or loose, and sufficient nutrients to ensure the growth of seedlings. Different types of crops have different requirements for the size and preparation of soil blocks. Mechanical control has been implemented.
When raising vegetable and flower seedlings abroad, a kind of nutrient pot compressed into a small block is often used. Some are called seedling trays or compressed cakes. When used, they absorb water and expand into a pot, and no culture soil or substrate is needed. This small block is very small in size, easy to use and carry, and labor-saving to transport. Moss, peat, and sawdust (pH value of about 5.5) are compressed into a cake with a diameter of 4.6 cm and a height of 5-7 mm. After swelling with water, it can increase to 4.5-5 cm. Other seedling containers are as follows.
(1) Seedling trays are mostly made of plastic, with a variety of sizes, depths and specifications to meet the requirements of different seedlings and seedling transplanters. There are usually drainage holes at the bottom of the tray. Some trays do not have small vertical and horizontal grids, while others do. There are generally about 100 grids, and each grid can grow one seedling.
(2) Seedling grids. For example, Yangquan City, Shanxi Province uses W-shaped plastic grids to combine rows of small squares to raise seedlings in the small squares. Applying this method can achieve an effect similar to raising seedlings with nutrient soil blocks.
(3) Seedling board Japan uses a special foamed resin seedling board for seedling cultivation. The board is 57.5cm long, 27.5cm wide and 1.6cm thick. This board is rich in nutrients and has strong water absorption, which is conducive to the growth of seedlings and suitable for mechanized planting. This board will decompose after a certain period of time in the soil.
(4) Seedling bag is a seedling bag made of polyethylene film. The bag is filled with peat, so it is also called peat bag. There are small drainage holes at the bottom of the bag, and it is equipped with a drip irrigation system to facilitate the growth of seedlings. The seedling bag is light and easy to transport. The Citrus Research Institute of Chongqing Xuyunshan Horticultural Farm uses seedling bags to cultivate citrus seedlings. The bag is 25cm long and 7cm wide. The two sides of the bottom are padded into a diagonal line. The middle part of the bottom is not sealed, so it does not fall off the soil but can penetrate water. After the soil is mixed with fertilizers such as cow dung residue, it is put into the bag. The roots of the seedlings are all in the bag, with many fibrous roots and lush branches and leaves. The plastic bag is removed when the roots are established.
(5) TODD seedling pots are made of polystyrene foam, which are very durable and can be reused 20 to 25 times. In order to allow air to enter through the small hole at the bottom of the pot, the end of the pot is supported by a T-shaped steel frame. TODD seedling pots use soilless culture substrates. The pot body is an inverted cone, which promotes the downward growth of roots, good root development, less root damage during planting, and is suitable for mechanized cultivation. This is widely used in the
cultivation of tomato, celery, melon and other seedlings in the United States. Nutrition and soilless culture
substrates A well-prepared culture substrate (including nutrition and soilless culture substrates) should have the following characteristics:
1. The organic matter used should have an appropriate carbon-nitrogen ratio and be fully decomposed;
2. It has good water holding capacity and aeration, with 35% to 50% water and 10% to 20% air after watering;
3. In order to retain nutrients, it should have a high cation exchange capacity (1 to 30 mmol/100g dry culture substrate);
4. 5. The culture
medium should be light and easy to move, but heavy enough to support the seedlings from falling over. Nutrition soil generally has three basic components, namely field soil, organic matter and coarse aggregates. Their proportions are determined by the type of seedlings, environmental conditions and the degree of difference between the three materials themselves. For example, Pennsylvania State University in the United States introduced several common soil mixtures as follows.
Heavy clay soil (Mongolian loam): 1 part soil, 2 parts organic matter, 2 parts aggregates.
Medium texture soil (loam or sandy Mongolian loam): 1 part soil, 1 part organic matter, 1 part coarse aggregates.
Easy soil (sandy loam): 2 parts soil, 2 parts organic matter.
The organic matter in the above mixtures is usually sphagnum peat, and the coarse aggregates are usually perlite. In order to ensure the growth of seedlings, superphosphate and limestone powder, calcium nitrate, potassium nitrate and a small amount of wetting agent are added to these mixtures.
There are many types of Zhang Ying culture soil commonly used in the UK. The composition ratio of the culture soil for sowing is: 1 part of clay loam, 1 part of peat, 1 part of coarse minerals. In each of the above mixtures, add 46kg of superphosphate, 23kg of limestone or chalk powder, and mix thoroughly.
Japan attaches great importance to the preparation of culture soil in seedling cultivation. For example, when preparing the physical and chemical properties of the culture soil commonly used for seedling cultivation of several major fruit and vegetable varieties, sandy loam or loam is often used for field soil, and compost, leaf mold, peat, sawdust or bark is commonly used for organic matter. Sawdust must be fully decomposed (mix 100kg of chicken manure and 7kg of nitrogen in every 1t of sawdust, and add water to ferment for more than two months) before it can be used.
The volume ratio of the preparation is: 2 parts of loam (3 parts for sandy loam), 1 part of organic matter, and then add an appropriate amount of chemical fertilizers. Generally, 75g of ammonium sulfate, 2.5kg of superphosphate, and 300kg of potassium sulfate are added to every 1m3 of soil.
The nutrient soil used for vegetable and flower seedling cultivation is generally 5-6 parts soil, 5-6 parts decomposed manure or some rice husk ash, sand, fertilizer, etc. The amount of soil used for seedling cultivation is large, and burnt soil is often used on site. The following are some of the ratios:
(1) 78%-88% burnt soil, 10%-20% decomposed compost, and 2% superphosphate are mixed;
(2) 1/3 burnt soil, peat, and loess soil are mixed;
(3) 1/2-1/3 burnt soil, 1/2-2/3 hillside soil or loess soil are mixed. When cultivating seedlings of mycorrhizal tree species, about 10% mycorrhizal soil and 2%-3% superphosphate can be added to the nutrient soil. The pH value of the nutrient soil for cultivating coniferous seedlings is 4.5-5.5, and the pH value of the nutrient soil for cultivating broad-leaved seedlings is 5.7-6.5.
The cultivation soil should be tested for various nutrient elements to ensure the growth of seedlings. If it is insufficient, it can be supplemented during preparation. For example, the citrus demonstration field in Lingling, Hunan, uses citrus container seedlings. The culture soil is made up of 3/4 decomposed sawdust and 1/4 river sand, and various fertilizers are added.
Introduction to seedling cutting propagation
Cutting propagation refers to a propagation method in which the in vitro plant vegetative organs (roots, stems, leaves, buds) are inserted into soil, sand or other substrates under suitable conditions, and the plant's regeneration ability is used to develop it into a complete new plant through artificial cultivation. The plant material that has been cut for cuttings is called cuttings. The seedlings obtained by cutting propagation are called cutting seedlings. Depending on the position of the cuttings, plant cutting propagation can be divided into root cuttings, leaf cuttings and branch cuttings. Branch cuttings are the most widely used cutting propagation method.
The cutting propagation method is simple, the materials are sufficient, and a large number of seedlings can be raised. It has become one of the main means of propagation for trees, especially precious garden tree species that are not strong or have a small amount of fruit. When propagating new plants through cuttings, you should understand that cuttings are part of the living plant and are part of the separated from a vital system. As a plant breeder, you not only need to increase the division into a whole, self-reliant plant.
1. Factors that affect the rooting
of the rooting process of cuttings. The formation of uncertain roots of cuttings is a complex physiological process. Whether the cuttings can take root and survive after cuttings is not only related to the internal factors of the plant itself, but also closely related to external environmental factors.
(1) Intrinsic factors that affect the rooting of cuttings.
① Biological characteristics of tree species. Different tree species have different biological characteristics, so their branches have different rooting abilities. According to the difficulty of rooting in cuttings, it can be divided into:
easy-to-root tree species such as willow, green poplar, black poplar, metasequoia, pond fir, fir, small-leaf boxwood, purple-leaf boxwood, forsythia, rose, eunuch, honeysuckle, ivy, Weishu, Nantian bamboo, red-leaf little-leaf boxwood, gold and silver wood, grapes, figs, pomegranate, etc. The more easy-to-root tree species such as arboriculata, cypress, Arhat cypress, Arhat cypress, Arhat cypress, Rose, Rose, Polygonum, Sophora, Tea, Camellia, Cherry, Wild Rose, Azalea, Pearl Plum, Water Wax Tree, Ashwax, Elderwood, Ligustrum, Elderwood, Privet, Elderwood, Privet, Cypriot, Oleander, Called Wild Peach, etc. The more difficult-to-root tree species such as arboriculata, Rose cypress, Japanese Five-needle pine, Swallow, Kulai, Stinky Toon, Junqianzi, Milan, Begonia, Jujube, etc. Tree species that are extremely difficult to take root are such as black pine, horsetail pine, red pine, camphor tree, chestnut, walnut, paulownia, goose palm, persimmon tree, elm, mechanical tree, etc. The difficulty of rooting in different tree species is only relatively speaking. With the deepening of scientific research, some tree species that are difficult to take root may become easy to take cuttings and will be promoted and applied in production. Therefore, when cultivating seedlings, you should pay attention to reference proven>
| |
