Vegetative branch species
Generally, according to its growth intensity and position in the crown, it can be divided into developmental branches (including competitive branches), long branches, thin branches and leafy branches (see branches).
developmental branch
The vegetative branches with vigorous growth, rich tissues, full buds and thick leaves are mostly extensions of the main branches outside the crown, which are the main branches to expand the crown and nourish trees. For young trees that are vigorous and fruitless, developing branches account for a large proportion. Because the leaves on the developing branches have strong photosynthetic capacity, rich organic nutrients are synthesized and used to build various organs, so that the crown and root system expand rapidly and blossom and bear fruit. When the trees enter the fruiting period, the proportion of developing branches decreases, mainly in the periphery of the crown. The growth length and thickness of developing branches are often regarded as one of the morphological signs of tree potential strength. When the soil is rich in fertilizer and water, the climate is suitable, or there are too many shortcuts, development branches occur more. Excessive growth of developing branches easily leads to canopy closure, poor illumination in canopy and few fruiting branches; Trees that grow too weak have few or no branches, weakened photosynthetic capacity, less nutrient accumulation, and can't blossom or flower without fruit. If the second and third developing branches germinated under the cutting of the main branch grow too vigorously and exceed the extended branches of the main branch, they are called competitive branches. Competing branches compete for water, nutrition and space, which often forces the main branches to change the extension angle and direction, interferes with the balance between the main branches and affects the whole tree. The occurrence of competitive branches is related to the characteristics of tree species and varieties. For example, apples and pears are prone to competing branches. In addition to replacing the original extended branches when the angle of the backbone branches is too small or the buds are too dehydrated or damaged, they should be pulled out as soon as possible.
Tender strip
A developmental branch that grows too vigorously but is not fully developed. Erect, long internodes, large and thin leaves, not full buds on branches, stopping growing late, mostly stimulated by hidden buds. Young trees tend to grow branches on the trunk, while adult trees mostly occur below the weak or stimulating parts of the trunk branches. Long branches grow rapidly, take up a lot of space, close the crown easily, consume a lot of water and nutrients, which is very unfavorable to the growth and fruit of fruit trees. Long branches bear fruit late, although they can be transformed into branches after control, but it takes a long time, and branches should be thinned as soon as possible. If old fruit trees have long branches, they are often used to update backbone branches or cultivate new branches. Excessive nitrogen application, excessive pruning or frequent irrigation will increase the number and intensity of overgrowth.
Weak branch
A vegetative branch that is thinner and shorter than the normal developing branch. Most of them occur in the inner or lower part of the crown, with poor illumination and nutrition conditions, poor differentiation in buds, sparse leaves, small and thin leaves after germination, thin buds or many blind nodes, and insufficient tissue. Pear, European plum, North China peach, chestnut, hawthorn, citrus pomelo, citrus and other varieties with strong branching ability, such as Zhuguang orange and apple, have fine branches. If the nutrition of the surrounding branches is good, it can provide some nutrients, and the weak branches may also be transformed into fruiting branches, but the weak branches are mostly consumable branches and will soon decline.
Ye congzhi
A vegetative branch with short internodes. There are drupes, drupes and other fruit trees. Generally, it is germinated from the bud in the middle and lower part of the developing branch, and it increases with the age of the tree. If the light and nutrition conditions are good, it can be transformed into fruiting branches; If it is inside or below the crown, it will decline year by year and die. Usually, apple, pear, citrus and other leafy branches need 4 ~ 5 large leaves to be transformed into fruiting branches, while peach and apricot need a certain thickness to be transformed into fruiting branches.
bud
The vegetative branches that grew in that year are collectively called new shoots. The part where spring occurs is called spring tip; After the growth of spring shoots stops or slows down, the part that continues to grow in summer is called summer shoots, and the part that grows again in autumn is called autumn shoots. Evergreen fruit trees may also germinate in winter. Deciduous fruit trees are mainly spring shoots, with a small number of summer shoots or autumn shoots; The new shoots with autumn shoots stop growing late, and the tissues are not full, so they are easy to lose water during wintering. Therefore, northern fruit producing areas often try to avoid late autumn shoots and try their best to make them stop early, grow early and mature early. Evergreen fruit trees, such as citrus, longan and loquat. Summer and autumn shoot growth is large, the nutritional function is high, and the proportion of transformed branches is high. In spring, summer, autumn and winter, the leaves at the joint of branches are small, and the buds between leaves are not full or have no buds (hidden buds). This morphological difference is obvious and not obvious because of different tree species and varieties. The new shoots of peach, grape, jujube, plum, litchi and citrus tend to have many branches, while apples, pears, persimmons, hawthorn, bayberry and longan have few branches.
The growth of new buds
Elongation growth depends on cell division and elongation of apical meristem population. Cell division only occurs at the top, and growth can continue to the lower internodes, and then gradually weaken. When cells grow, they deform and thicken the cell wall, and further differentiate into epidermis, cortex, primary xylem and primary phloem, pith, stele sheath and other tissues. In a growing season, the growth of new shoots of deciduous fruit trees is generally divided into three stages (see figure): ① New shoots begin to grow. After the leaf buds germinate, the young leaves separate, expand and lengthen the internodes. The leaves grown in this period are small and tender, with more water, water-soluble sugar and non-protein nitrogen and less starch. The photosynthesis of young leaves is weak, and it can't produce a lot of organic matter, so the nutrition is in the consumption stage. Therefore, the amount of nutrients stored in trees last year had a great influence on the growth potential of new shoots. ② vigorous growth period of new shoots. The young leaves at the top are rapidly separated, the internodes are prolonged, the number of leaves is increased, the area of a single leaf is increased, and the photosynthesis of leaves is enhanced, which can produce a lot of nutrients. At this stage, the growth of new shoots is large and nutrient consumption is high, so the carbohydrate content of new shoots is still at a low level, and the tree enters a period in which non-protein nitrogen is dominant. The length of new shoots depends on the length of vigorous growth period. There is no obvious vigorous growth period of new shoots in branches and leaves and short branches. ③ New buds grow slowly and stop growing. When the new shoots differentiated into buds have been formed, the growth point of the new shoots has accumulated a certain amount of growth inhibitors, or the external environmental factors gradually tend to be unfavorable to growth, the cell division of apical meristem slows down or even stops, and the false terminal buds form at the top of the new shoots, and the cell elongation also slows down and stops. At this stage, the leaves of the new shoots have fully grown from bottom to top, and a large amount of carbohydrates produced and accumulated began to transfer to the outside of the new shoots. At the same time, starch and hemicellulose accumulated in new shoots, and protein synthesis was also strengthened. Then the cork layer is produced, the cell wall in the mechanical tissue is filled with lignin, and the new buds change from grass to wood and enter the mature stage.
Factors affecting the growth of new shoots
Mainly includes: ① variety and rootstock. Due to genetic differences, the growth intensity of new shoots varies greatly. The new shoots of short-branched varieties grow slowly and the internodes are short and compact; Dwarfing rootstocks in rootstocks have obvious dwarfing effect on aboveground parts, and the growth of new shoots is inhibited to some extent. In dioecious fruit trees, such as ginkgo and kiwifruit, the new shoots of male plants generally grow vigorously and in large quantities; The growth potential of female plants is weak and the growth amount is small. ② Endogenous hormones. The growth of new shoots is the result of different levels and balance of growth hormones such as auxin, gibberellin, cytokinin, abscisic acid and ethylene. At the early stage of shoot growth, with the help of cytokinin, auxin and gibberellin from root system, shoot growth is accelerated. With the elongation of branches, the growth and senescence of leaves, the levels of abscisic acid and ethylene are constantly rising, so the growth slows down or even stops. ③ Storage nutrition. The organic nutrition needed in the early stage of new shoots mainly comes from the storage nutrition of trees in the previous year. After the leaves grow out and the carbohydrates are made, the organic nutrition of that year is switched to use. ④ Environment and culture conditions. High temperature in spring is beneficial to the growth of new shoots, and sufficient nitrogen fertilizer and water can prolong the growth of spring shoots. Deciduous fruit trees in the north, with proper drought in autumn, can make new shoots mature and lignified early, which is conducive to safe wintering. The ultraviolet ray is too strong, which inhibits the growth of new shoots, shortens internodes and dwarfs the whole tree; Red light helps the new buds to elongate. Insufficient light will weaken the new shoots.
Excellent strain
See the strain.