An approach based on a high temperature tolerant Cymbidium mutant to understanding flower bud blasting

在本研究中，我们利用一个耐高温突变体和另一个不耐高温品种，研究了蕙兰花蕾如何以及为什么会被高温炸裂。从一个分生克隆中分离出的耐受性突变体，其体细胞染色体数目为2n=40，与其原品种（红宝石之眼’金星’）相同。该突变体产生的花粉量较少，这表明在小孢子发生过程中发生了一些异常事件。在分生组织培养的突变株中，也发现了不耐突变株。因此，我们试图将它们与耐受性突变体区分开来。然而，这只适用于非常有限数量的突变体。由于大多数突变株可能是由于1992年进行的分裂的后效而没有开始花序。基于上述原因，对不耐性品种（Sazanami’Haru-no-umi’）进行了进一步的试验。在低温条件下（20 C天/14 C夜），在高温条件下（30 C/24 C），花蕾中isic acid（ABA）含量增加了5倍以上。相反，控制组的水平保持在初始水平附近。在低温条件下，外源ABA降低了花芽的生长速度。一些经过aba处理的花蕾被枯萎，导致开花减少。赤霉素酸（GA_3）可消除ABA的抑制作用。我们还研究了一种GA生物合成抑制剂uniconazole对花芽发育的影响。单硝唑处理的花蕾比对照的花蕾进化出更多的乙烯，最终被炸坏。硝酸镓与硫代硫酸银联合施用可完全逆转硝酸镓的作用。这些结果揭示了GA对花芽发育的参与，也支持了前人研究提出的高温导致花芽GA缺乏和/或GA不敏感，从而通过刺激乙烯进化导致花芽爆破的假设。少

In this research we have examined how and why Cymbidium flower buds become blasted by high temperature using a high temperature tolerant mutant and another non-tolerant cultivar. The tolerant mutant isolated from a mericlone revealed the same somatic chromosome number of 2n=40 as its original cultivar (Ruby Eyes 'Golden Star'). The mutant produced a smaller amount of pollen, which suggests some abnormal events in microsporogenesis. Among mutant plants propagated by meristem culture, non-tolerant ones were also found. Therefore, we have tried to distinguish them from tolerant mutants. However, this was only done for very limited number of mutants. Because, most mutant plants did not initiate inflorescences probably due to after-effect of division conducted in 1992For the above reason, further experiments were carried out with the non-tolerant cultivar(Sazanami 'Haru-no-umi'). When plants grown at low temperatures(20ﾟC day/14ﾟC night)were transferred to high temperatures(30ﾟC/24ﾟC), absc … More isic acid(ABA)content of flower buds increased up to 5 fold of the initial content. Onthe contray, that of control ones remained around the initial level. Under low temperature conditions, exogenous ABA lowered growth rate of flower buds. Some of ABA-treated flower buds became blasted resulting in reduced flowering. Inhibitory effect of ABA was abolished by gibberellic acid(GA_3).We also examined effect of an GA biosynthesis inhibitor uniconazole on flower bud development. Uniconazole-treated flower buds evolved much more ethylene than control ones and finally became blasted. The effect of uniconazole was completely reversed not by GA_3 treatment but by combined application of GA_3 with silver thiosulfate. These results revealed participation of GA in flower bud development, and also supported the hypothesis proposed based on previous studies that high temperature causes GA deficiency and/or GA insensitivity of flower buds, which in turn leads the flower buds to blasting though stimulating ethylene evolution. Less