What is cuttage propagation?

Cutting propagation is a kind of asexual propagation, that is, the vegetative organs such as roots, stems and leaves of plants are used as cuttings and inserted into the substrate to make them take root and branch to grow into complete new plants, so as to obtain seedlings completely consistent with the genetic characteristics of the mother plant. Cutting is the most commonly used method in asexual reproduction, because it has wide sources, low cost, fast seedling formation and simple method. Of course, cuttings obtained by cutting also have some shortcomings, such as poor root system, shorter life span than seedlings and lower resistance than grafted seedlings.

(A) the mechanism of cutting rooting

First of all, plant cells are totipotent, that is, each cell has the same genetic material, and they have the potential to form the same plant under appropriate environmental conditions. Secondly, the plant has the function of regeneration, that is, when a part of the plant is injured or cut off and the whole plant is damaged, it can show the function of making up for the damage and restoring coordination. Therefore, when roots, stems, leaves, etc. Due to the totipotency and regeneration function of plants, stems and leaves will grow from roots, roots from stems, and stems and roots from leaves. That is, after the branch leaves the mother, the cambium, secondary phloem, vascular fiber and pith in the branch can form the primordium of adventitious roots, and then develop into adventitious roots. When roots are used as cuttings, parenchyma cells differentiate into adventitious buds in the cortex of roots, thus growing into stems and leaves.

(2) Factors affecting the survival of cuttings

Whether the cuttings of plants can take root and how fast they can take root have a great relationship with the plants themselves and cutting conditions, and are also affected by external environmental conditions.

1. Internal factors affecting the rooting of cuttings

(1) Genetic characteristics of the plant itself The rooting ability of cuttings varies with the genetic characteristics of the mother plant and varieties. According to the difficulty of rooting, ornamental trees can be divided into three categories:

Tree species easy to take root: cuttings take root easily and quickly. Such as winter jasmine, rose, gardenia, oleander, Platanus acerifolia, Buxus macrophylla, coral tree, banyan tree, pomegranate, rubber tree, Brazilian iron, rich bamboo and so on.

Difficult to take root: Cutting can take root, but it takes root slowly and requires high technology and management. Such as camellia, osmanthus, cedar, maple, nandina, cypress and so on.

It is extremely difficult to take root: cuttings cannot take root or are difficult to take root, and generally cannot be propagated by cutting. Such as peach, wintersweet, pine, begonia, bauhinia, beech, Liquidambar formosana, bamboo and so on.

(2) The age of the mother tree and the rooting ability of cuttings decreased with the increase of the age of the mother tree, and the older the mother tree, the lower the rooting ability. Because with the increase of the age of the mother tree, the stage development age is older, the vitality decreases, and the fertility of the cells decreases. On the contrary, young mother trees are easy to take root because of their young developmental age, favorable nutritional status and hormones, and strong meristematic ability of cells.

Similarly, the age of the mother branch also has a great influence on the rooting of cuttings. Young 1 ~ 2-year-old branches are easier to take root than perennial branches, and tender branches (semi-lignified branches) are easier to take root than hard branches (lignified branches). Of course, cutting is not only affected by the age and maturity of the mother branch, but also varies with different tree species, cutting time and methods. Trees that are easy to take root, such as poplar, willow, oleander, etc., can also be cut with perennial branches, and semi-lignified branches are often used in the growing period.

(3) The position and nutritional status of the mother branch. Because the position of the mother branch is different, its nutritional status and stage development age are different, which has certain influence on the rooting of cuttings. Generally, the branches on the sunny side of the crown are better than those on the shady side of the crown, and the sprouting branches at the base are better than those on the upper crown. This is due to the vigorous growth, rich nutrition and rich tissues of the Yang branch and the sprouting branch, and the tender development age of the sprouting branch at the base is conducive to rooting.

(4) The cuttings taken from different branches on the same mother branch have different roots in different parts, and the base and middle parts are generally better. Some tree species can improve the rooting rate by cutting with heel when cutting with hard branches.

In addition, the thickness, length, amount of leaves left and the inhibitory substances inside the cuttings also have certain effects on rooting.

2. External factors affecting the rooting of cuttings

(1) temperature has a great influence on rooting of cuttings, and rooting is faster when the temperature is suitable. The suitable temperature for different tree species is different, and the requirements for suitable temperature for rooting are also very different. Most tree species are suitable for rooting at 15 ~ 25℃, while tropical tree species, such as jasmine, Milan, rubber tree, dragon's blood tree, bamboo and banana, have higher temperature requirements, all above 25℃. Osmanthus fragrans, camellia, rhododendron and oleander are more suitable in the range of 15 ~ 25℃, and willow can be lower. Generally, the softwood cutting in the growing period needs higher temperature than the hardwood cutting in the dormant period, and the optimum temperature is about 25℃.

In addition, if the substrate temperature can be higher than the air temperature, it is conducive to rooting, and it is appropriate to be higher than 3 ~ 5℃. When the temperature is lower than the growth temperature and the substrate temperature is slightly higher, it is most favorable at night, and the rooting speed is faster, while the aboveground part grows relatively slowly. Especially in the dormant period, cuttings germinate branches and leaves behind the roots, which is beneficial to the nutrient consumption of cuttings and gives priority to the growth of roots. After the branches and leaves germinate, the water absorbed by the roots of cuttings tends to be balanced with the water consumed by the aboveground parts. If heating wires are laid under the substrate for heating, rooting can be effectively promoted.

(2) Humidity, air humidity and substrate humidity are the keys to rooting. It is difficult for cuttings to absorb water from the substrate before rooting, and cuttings themselves, especially those with leaves, consume a lot of water due to transpiration, which easily loses water balance and leads to cuttings drying up. Therefore, it is extremely important to maintain high air humidity and certain substrate humidity.

First of all, we should ensure high air humidity and minimize the transpiration of cuttings. At the same time, it is necessary to keep the humidity of the substrate moderate, ensure the humidity needed for rooting at the base, and prevent the substrate from being poorly ventilated, low in oxygen content and low in temperature, prolong the rooting time, and even make the cutting base rot due to hypoxia and suffocation. Generally, the water content of the substrate is 50% ~ 60% of the maximum water holding capacity.

The contradiction between air humidity and substrate humidity can be well solved by using closed cutting bed and automatic intermittent spraying bed insertion. Automatic intermittent spraying of electronic leaves in full sunshine can make the air humidity basically saturated, minimize leaf transpiration, and at the same time, the leaf temperature will drop and the substrate humidity will not be too high. Moreover, the auxin formed by leaves will be transported to the base under full sunlight, which will induce photosynthesis and produce nutrients for cuttings to take root. It is especially suitable for cutting twigs with leaves in the growing period. However, the survival rate of cuttings can also be improved by sealing and moisturizing the closed seedbed with film and improving the air humidity, and adjusting the temperature combined with shading facilities and proper ventilation.

Of course, as the cuttings gradually take root, it is necessary to adjust the humidity in time and gradually reduce the air humidity and substrate humidity, which is beneficial to the growth of roots and can achieve the purpose of hardening seedlings.

(3) The influence of illumination on cutting has two aspects. On the one hand, moderate light can increase the temperature of substrate and air, promote the formation of auxin and induce rooting, promote photosynthesis to accumulate nutrients and accelerate rooting. On the other hand, light will make the cutting temperature too high, and the water transpiration will be accelerated, leading to wilting. Therefore, in the cutting period, especially in the early rooting period, it is necessary to shade properly to reduce water loss and spray water to cool and humidify. However, with the growth of root system, the cutting time should be gradually extended. If intermittent spraying can be used, cutting can be carried out under full sunshine.

(4) The substrate does not necessarily need nutrients, but it should be warm and moist, loose and breathable, free from pests and diseases, light in texture, convenient to transport and low in cost. Commonly used in production are: rice bran ash, perlite, vermiculite, peat, coconut bran, sand and so on.

(3) Methods of promoting cuttings to take root

Because the rooting ability and rooting speed of different tree species cuttings are different, artificial measures can be taken to promote some tree species that are not easy to take root and take root slowly in production to improve the rooting rate. Commonly used methods are:

1. Chemical treatment

Treatment with auxin as rooting promoter can effectively promote cuttings to take root early and more. Commonly used varieties are NAA, IBA, 2,4-D, ABT rooting powder, etc. Among them, indolebutyric acid has strong efficacy, stable properties, not easy to destroy, the best effect, but the price is higher; NAA has low cost and good rooting effect. Indobutyric acid mixed with naphthylacetic acid has better effect than single dose. However, the application of rooting agent should be within a certain concentration range, too high will inhibit rooting. Naphthylacetic acid, in particular, has strict standards for different tree species, and it should be tested before use to find the most suitable dosage. In addition, the treatment concentration also varies with the treatment time. Generally, the concentration of quick immersion is high and the concentration of long immersion is low.

How to use rooting agent:

(1) aqueous solution method, also known as solution impregnation method, first dissolves the powdery rooting agent, then dilutes it with water to make the stock solution, and then prepares it into different concentrations according to needs. Generally, the hard branches are soaked in 20 ~ 200mg/L for several hours to 1 day and night; Generally, the new shoots are ground at the rate of 10 ~ 50 mg, and soaked for several hours day and night to 1. At present, the rapid impregnation method of high concentration solution is mostly used in production, and the concentration is generally 300 ~ 2000 mg. Soak the cuttings into the solution quickly (5 ~ 10 second).

(2) After the rooting agent is dissolved by powder method, it is mixed with talcum powder to make a paste with a concentration of 500-2000mg/L, and then dried or dried in the shade at 60-70℃ and ground into powder for later use. When in use, the base of the cutting is soaked in clear water, and then dipped in powder for cutting.

In addition to auxin and other root promoters, it can also be treated with B vitamins, sucrose, potassium permanganate and rare earth elements, which also has certain effects. In the production, vitamin B 1 1 ~ 2mg was used for grinding 12h, potassium permanganate was soaked in 0. 1% solution for 5 ~ 10h, and sugar was soaked in 2% ~ 5% solution 10 ~ 24h. Treatment should be carried out according to different tree species, and the concentration and treatment time should be adjusted appropriately.

2. Physical treatment

(1) Carry out mechanical cutting or girdling at the base of the branch used as cutting. About 20-30 days before cutting, the nutrients and auxin made in the upper part of the branch are prevented from being transported downwards, while the cutting is left in the branch, which can effectively promote rooting after cutting.

(2) Yellowing treatment: Black paper, cloth or film is used to shade the branches used for cutting, so that the branches grow in the dark for a period of time, and then turn yellow and soft due to lack of light, thus promoting the development of root cells, delaying the development of bud tissues, and finally promoting the rooting of cutting.

3. Strengthen comprehensive management

The management of transplanting bed is the key to the success or failure of cutting. If we can comprehensively apply modern technology and strengthen management, the rooting rate can be greatly improved. The commonly used methods are geothermal heating method, which is suitable for cutting in winter and spring, such as winter hardwood cutting of rose and cypress. All-sunshine intermittent spraying method is suitable for twig cutting in growing period, especially in high temperature season. For example, cutting evergreen broad-leaved trees in summer can effectively prevent cuttings from wilting and rotting and take root early. In addition, it can also be combined with substrate disinfection, spraying bactericide on the bed during cutting, moderate shading and the above cutting treatment.

(4) Cutting method and cycle

1. hardwood cutting

Also known as dormant cutting. Select lignified 1 ~ 2-year-old branches as cuttings. It can be done in late autumn and early winter after plant dormancy, or before germination in early spring and after soil thawing. It depends on the tree species and climatic conditions in each area. Generally speaking, cuttings should be picked in autumn and stored in spring in cold and dry winter areas in the north, and transplanted in autumn in warm and humid areas in the south, which can save the storage of cuttings. Those with strong cold resistance can be inserted early, and those with strong cold resistance can be inserted early.

The cutting length is generally 10 ~ 20cm, which can be slightly longer in arid areas in the north and slightly shorter in humid areas in the south. The cutting is 0.5 ~ 1 cm away from the terminal bud to protect the terminal bud from dehydration and drying. The undercut is generally near the internodes, and each ear generally has 2 ~ 3 or more buds. In addition, the upper end of the cutting is cut into an oblique mouth, which is convenient to identify the upper and lower ends when cutting, and the other is to prevent the upper incision from accumulating water and becoming moldy. The lower end can be cut into a flat mouth or an oblique mouth, both of which have their own advantages and disadvantages. Although the oblique mouth has a large contact surface with the substrate, absorbs a lot of water and is easy to survive, it is easy to form partial roots; Relatively speaking, the roots of the flat mouth are slightly slower, but the roots are evenly distributed.

The depth of cuttings inserted into the substrate also affects the survival rate. If the cuttings are inserted too deep, because of the low ground temperature and insufficient oxygen, it is not conducive to rooting and affects the germination of tender buds. Cutting is too shallow, cutting is exposed too much, evaporation is large, and it is easy to lose too much water and dry. Generally, the insertion matrix accounts for about 1/3 ~ 1/2 of the cutting length, and it is suitable to be deep in arid area and slightly shallow in humid area.

2. Soft cuttings

Also known as growth cutting. Semi-lignified multi-leaf cuttings were carried out in summer and autumn during the vigorous growth period.

Softwood cutting takes root faster, has higher survival rate and is widely used than hardwood cutting. However, the choice of branches should not be too tender, otherwise the buds are not fully mature, and the cuttings are easy to lose water and wilt or rot. Don't be too old, otherwise the activity will be reduced and it will be difficult to take root. When there are many leaves in shoots, it is beneficial to accumulate nutrition and promote rooting, but it is not advisable to leave too many leaves, otherwise it will easily lose too much water and make the cuttings wilt. In order to reduce the transpiration of leaves, cutting leaves can also be cut in half, such as sweet-scented osmanthus and camellia cuttings; Or roll larger leaves into tubes, such as rubber tree cuttings. Shoots should be inserted when they are picked, and the tops of branches should usually be cut off because they are too tender.

3. Leaf bud insertion

Some tree species can also be inserted with leaf buds. That is, a leaf attached to a short stem with axillary buds or only phloem as a cutting can produce adventitious roots at the base of the petiole, and the leaf buds can germinate into new branches to form a complete plant. This method can save cuttings and take root faster, but it requires higher management, especially to prevent excessive evaporation of water. Commonly used leaf buds are camellia, rhododendron, osmanthus fragrans, rubber tree, gardenia, citrus and so on.

Step 4 cut the roots

Some tree species are not easy to take root, but it is easy to form adventitious buds and plants by root cutting, which can be propagated by root cutting, such as Carya cathayensis, Peony, Albizia Albizzia, Haizhou Changshan, Toona sinensis, Lilac, Begonia and Luanshu.

Roots should be taken from young trees when cutting roots, because the ability of old roots to grow into plants is poor, and roots can also be taken in combination with spring and autumn when seedlings leave the nursery. Choose the root with the thickness of 0.5 ~ 1.5 cm, and cut it into 6 ~ 10 cm. Spring planting in the north (if the roots are harvested in autumn, they can be buried and preserved), and planting can be dug in the south. In order to prevent the polarity from being reversed, when cutting roots, the upper mouth can be cut flat and the lower mouth can be cut obliquely. Irrigation should be done immediately after planting, and the nursery should be kept moist.