珍稀濒危植物珙桐种子休眠萌发过程中内源激素的变化

Changes on the edogenous phytohormone content of the Davidia involucrate seed during dormancy and germination process

珙桐是我国特有珍稀濒危植物,休眠期长且具二次休眠现象。将处于休眠萌发过程中的珙桐种子依据胚根长度划分为4个阶段,利用高效液相色谱(HPLC)测定各阶段种子及其内果皮中ABA(脱落酸)、GA(赤霉素)、KT(细胞分裂素)、IAA(3-吲哚乙酸)4种内源激素含量,分析其比值动态变化,并与幼苗阶段进行比较。结果显示:未破壳种子的内果皮中内源激素含量以ABA最高,其次是GA、IAA、KT,随着种子破壳后四种激素含量显著降低。除ABA外,种子中GA、IAA和KT含量随着胚根的伸长逐渐升高,但仍低于幼苗阶段。此外,随着胚根伸长,种子中GA/ABA、IAA/ABA、KT/ABA比值逐渐增大,其中以GA/ABA的变化最显著。因此,珙桐种子的休眠和萌发可能主要受ABA和GA的平衡和拮抗来调控。

Davidia involucrate is an ornamental tree native to China and one of the very rare and endangered plants, which has double dormancy as well as a long dormant period. In the study, dormancy and germination process of Da vidia involucrate seeds was divided into four stages according to radicle length. The changes of ABA（Abscisic acid）, IAA（Indole-3-acetic acid）,OA（Gibberellin） and KT（Kinetin） content in seeds and endocarp were determined by using HPLC among four stages. In addition, the dynamics on GA/ABA, IAA/ABA, KT/ABA and KT/IAA ratio were analysed among four stages. Finally, above-mentioned data were compared with those in seedlings stage. The results showed that： （1）the endogenous hormones content order is ABA〉GA〉IAA〉KT in endocarp of uncracked seeds,the four endogenous hormones content decreased significantly after seeds were cracked; （2）except ABA,GA, IAA and KT contents in seeds increased gradually with radicle elongation. However, the GA,IAA and KT contents were less compared to those in seedlings; （3）in addition,GA/ABA,IAA/ABA and KT/ABA ratio in seed increased gradually with radicle elongation. The change in GA/ABA ratio was greatest than the other two ones. So it is sug gested that the trade-off between ABA and GA contents could control the dormancy and germination process in Da vidia involucrate seed.