Studies On Physiology And Biochemistry Of Embryo Development In Litchi (litchi Chinensis Sonn.)

The development condition of litchi embryos is not only closely related with fruit set, but also has direct effect on production, taste quality and processing quality. It has great theoretical and practical significance to study the physiological and biological mechanism of embryo development in litchi, which helps find out the expressive law from gene to character, select litchi varieties, control fruit seeds, improve fruit quality, raise setting rate and increase litchi production. This thesis works on the physiological and biochemical basis of litchi embryo development in the aspects of polyamines, biomacromolecules , plant hormones, phenolic inhibitors and specific proteins. 1 Relationship of litchi embryo development with polyamines and biomacromolecules The development of embryo is closely related with the changes of the contents of three polyamines (PAs) and their proportion in litchi ovules. Experiments showed that the contents of putrescine (Put)~. spermidine (Spd) and spermine (Spin) in normal ovules were higher thap those in abortive ones during the whole embryogenetic process. The highest levels were reached 7 days after anthesis (DAA), with Put being the richest of the three, then they declined. However, Spin increased slightly at 22-3IDAA (from globular stage to heart stage) in normal ovules. But such a phenomenon did not appear in the abortive ones. Spd and Spin evidently dropped more rapidly in the abortive ovules than those in the normal ones, 83 which indicats that lower contents and more rapid decrease of Spd and Spin during the embryogenetic process might have a close relationship with embryo abortion. The studies also showed that low ratios of n (Spd+Spm) ,i?Put) and n(Spni) n?PAs) might hinder embryo development. PAs contents hit the peak before the contents of DNA and protein reached maximum, which suggests that PAs might affect embryo development by regulating the synthesis of biomacromolecules. 2 Relationship between litchi embryo development and endogenous hormones The relationship between embryonic development and endogenous hormones in the ovules of 揕uhebao?(a variety with complete embryonic abortion), 揥uye?(a variety with normal embryonic development) and 揕anzhu~?(a variety with both normal and abortive embryo development) were studied. The results showed that in 揕uhebao?ABA content and the ratios of n (ABA) n?IAA+GA,+3) and n (ABA) nt (CTK) remained at a relatively high level at the beginning stage of the embryonic abortion. IAA GA1+3and CTK content began to drop rapidly on 7DAA and remained at a relatively low level during the embryonic abortion period. In 揥uye?, ABA content began to decrease sharply on 7DAA and during the following embryonic development stages the content and the ratios of n (ABA) n?IAA+GA1+3) and n (ABA) n1 (CTK) kept obviously lower than those in 揕uhebao? The contents of IAA , GA1+3, especially CTK in 揥uye?were much higher than those in 揕uhebao? In 揕anzhu? the contents of IAA , GA1+3 and ABA in normal ovules reached the highest level 7DAA, then decreased. IAA and GA1+3 increased again from heart to torpedo stage, and CTK content kept high before the globular stage. However, ABA in abortive ovules maintained a relatively high level, but IAA and GA)+3...