The concentration of nutrient distribution and transportation is a characteristic of fruit tree's self-regulation function and a necessary condition to ensure the formation of key organs. According to the change of phenology, the nutrient concentration and distribution center of deciduous fruit trees can be divided into four periods in two years.
(1) germinates and blooms. This phenological period is the first peak of physiological activity in the annual cycle of fruit trees, and its nutrient distribution center focuses on germination and flowering. This period mainly uses the nutrients stored in the previous year, which is in the consumption stage, with flowering consuming the most. If too many flowers consume a lot of nutrients, it will inevitably affect the growth of new shoots and roots, and then affect the nutrient accumulation in the current year and the yield in the next year. In production, measures such as fertilization in early spring, irrigation and early thinning of flowers and fruits are often taken to supplement nutrition, adjust flower quantity, promote nutritional growth and improve fruit setting rate.
(2) shoot growth and fruit development. The growth of new shoots and the development of young fruits are almost the same in time, and the physiological activities are particularly vigorous, which requires a lot of nutrition and the nutrition competition is fierce, so this period is a tense stage of nutrition distribution in a year. At this time, the nutrition distribution is concentrated on fruits and branches and leaves. If the nutritional growth is too strong, it will inevitably affect the fruit development, and even cause a large number of physiological fruit drops due to insufficient nutrition; On the other hand, if there are too many fruits and a lot of nutrients are consumed, the growth of new shoots will be obviously inhibited.
Zhang Wencai (1962) and others applied phosphorus to Huanong 1 apple. The results showed that when the bud just germinated, phosphorus transported to the short fruit branches more than to the top. After the first physiological fruit drop on May 6th, it was determined that the content of pruned treetops was more, and the content of untrimmed or flower-thinning pruned treetops was less. On May 30th, the new shoots grew slowly and delivered less nutrients to the top than the short fruit branches. The p value of the input extension branch on the strong tree is greater than that of the result branch, but the difference on the weak tree is very small. When the content of fruit drop is less than that of fruit setting, the weaker the tree potential, the less P is input into the fruit (
Table 2-2 Apple Tree Huanong 1
)。 It can be seen that the more fruits are left, the greater the contradiction between branch extension and fruiting, and the more intense the competition between vegetative growth and reproductive growth for nutrients. Lack of fertilizer and water can make the supply of fertilizer, water and nutrients necessary for the growth of new shoots occupy a dominant position, leading to an increase in physiological fruit drop.
(3) Young fruit development and flower bud differentiation. During this period, the growth peak of new shoots has passed, most of the short branches have stopped growing and started to enter the stage of flower bud differentiation, while the fruit is accelerating its growth, and the distribution center of nutrients has shifted from the growth of new shoots to flower bud differentiation and fruit development. In the competition for nutrients, it is mainly manifested in the contradiction between flower bud differentiation and fruit development. The main source of nutrition is made and supplied by the vegetative organs formed in that year. If the new shoots continue to flourish in the later stage, the impact on flower bud differentiation and fruit development is particularly serious. Therefore, it is beneficial to flower bud differentiation and fruit development to control the vigorous growth of branches in the later stage and apply phosphorus and potassium fertilizer reasonably.
(4) Fruit ripening and root growth. When the vegetative growth gradually stopped, the fruit grew rapidly, and the biochemical changes of its contents accelerated, most of the assimilated nutrients continued to be transported to the fruit, and a small part moved to storage organs such as trunks, backbone branches and roots. When the fruit is harvested, most of the reflux is concentrated on the fruit trees, and the roots turn into the prosperous period before winter. The key of this period is to strengthen the late management and protection of leaves, promote their assimilation function, improve the photosynthetic intensity and accumulation of leaves as much as possible, improve the nutrient storage capacity of trees, and create material conditions for root growth, flower bud differentiation and next year's growth and development.
In a word, nutrients are the basis of the growth and development of fruit trees and the whole life activities. Only by fully understanding the distribution and operation rules of nutrients and taking effective comprehensive cultivation measures can we enhance the synthesis and accumulation of nutrients, make them suitable for vegetative growth and reproductive growth, and solve the contradiction between nutrient distribution and competition in each development stage in time, so as to obtain high-yield, stable-yield and high-quality fruits.