The Effects And Cytochemistry Mechanism Of Ethylene-induced Floral Sex Differentiation In Litchi

Litchi chinensis Sonn. belongs to Sapindaceae family. Litchi flower is miscellaneous, the male flower, female flower and hermaphroditic flower growth on one tree. Litchi has a large quantity of flowers, but its proportion of male and female flowers is small, ripe fruit are little, so people think only one tenth of the litchi flowers reproduce. Therefore, through application of the exogenous regulators to increase the proportion of male flowers, and to improve production, is of great significance.We took"Yuan Hong"litchi for the materials,sprayed ethephon on litchi trees, used transmission electron microscopy and high-performance liquid Chromatography skills etc. We compared the first batch of differentiating litchi flowers which were treated with and without ethylene. The main experimental results are as follows:1 The morphology of the first batch of differentiating litchi flowers which were treated with and without ethylene. Used the hand anatomy and microscopy skill, we studied the external morphology of the developement process of litchi flowers. The results showed that: The litchi flower bud differentiation is a complex and orderly process. Ethylene significantly delayed the transformation from vegetative growth to reproductive growth. After the side-inflorescence primordium formed, growth speed of litchi flowers which were treated with ethylene was quickened. Ultimately, female followers of the first batch of litchi flowers which were treated with ethylene were increased, their pistils developed rapidly, their stamens developed slowly or undeveloped. But most of the first batch of litchi flowers which were treated without ethylene were male.2 The observation of the ultrastructure of stamens in the first batch of differentiating litchi flowers which were treated with and without ethylene. We used transmission electron microscopy to study the ultrastructure. The results showed that: The stamens which were treated with ethylene, developed slowly or undeveloped, their microspores was malnutrited, and microspores'development was delayed, so the stamens were unable to win the competition of nutrition with pistils, their tapetum cells disintegrated early in the microspore tetrad period. The way of the tapetum cells'disintegration was different from the tapetum cells in anthers which were treated without ethylene. It was still quadrangular, but the tapetum cells of the anthers which were treated without ethylene shrinked, their disintegration may have different procedure.3 The determination and analysis on the levels of endogenous hormones in the first and second pairs of ripe leaves of litchi which were treated with and without ethylene. We used skills of plant extraction and high-performance liquid chromatography to determinate the level of endogenous hormones. The results showed that: Exogenous ethylene changed the proportion of endogenous hormones of litchi. The leaves with ethylene treated have more GA, IAA and ABA, but less ZT. The comprehensive effectiveness of these changes, delayed the transformation from vegetative growth to reproductive growth.4 The analysis on the distribution of calcium in stamens of the first batch of differentiating litchi flowers which were treated with and without ethylene. We used cytochemical technology of potassium pyroantimonate and calcium, combined with transmission electron microscopy to study the distribution of calcium. The results showed that: During the sporogenous period, the lack and abnormal distribution of calcium in the antheres which were treated with ethylene were not conducive to development. During the microspore tetrad period, the lack of the calcium in the fringe of calloses and the cell walls of the tapetum cells was not conducive to the development. The lack of the calcium in cell walls of the tapetum cells might be the reason why they disintegrated early. When the microspores started to develop, the calcium in the anthers which were treated with and without ethylene both reduced. During the mononuclear microspore period, too much calcium in the tapetum cell walls of the anthers which were treated with ethylene might be the cause which making the tapetum cells has whole cell walls and do not shrink. However, the whole cell walls were not conducive to provide nutrition to the microspores, led the microspores unable to develope normally. During the binucleate microspore period, the reduction of calcium was advantageous to development, but too little calcium led the cell membrances of all stratums of the anthers disintegrated, the anthers became atrophy, the microspores had not enough space to develop.