光和GA_3诱导番茄种子萌发过程中内源ABA的变化

Changes of Endogenous ABA Level During Germination of Taiwan Red Tomato Seeds Induced by Light and GA_3

外源GA_3和红光都能有效地诱导台湾红番茄种子萌发;外源ABA对光诱导萌发有明显的抑制作用。白光和红光诱导萌发过程中内源ABA水平急剧降低,而在黑暗或远红光下则一直保持在与风干种子中原有的高水平。1 mol/L HCl酸化1h后加100 ppm GA_3诱导萌发时内源ABA含量也随培养时间的延续而明显下降。

The role of ABA in the germination of light sensitive seeds and the cause of degradation of endogenous ABA during induced germination are not quite clear. It was shown previously that Taiwan Red tomato seeds were typical light sensitive seeds, and that exogenous GA_3 was able to induce seed germination. To study the changes of ABA level of germinating and non-germinating seeds, air-dry seeds were incubated at 25℃ under white light, red light, far-red light and in the dark for 1,2 or 3 days with water, GA_3 solution or GA_3 solution acidified with 1 mol/L HCl (1 h), respectively. The ABA contents in extracts were detected by GC with a hydrogen ion flame detector and by wheat coleoptile straight growthe assay. The results showed that the airdry seeds had high ABA level (about 650μg/g air DW) which could inhibit seed germination. The level of endogenous ABA fell rapidly in seeds incubated under white light and red light, but remained unchanged in seeds incubated in the dark or under far-red light. When seed germination was induced by 100 ppm GA_2 acidified with 1 mol/L HCl for 1 hour, the content of endogenous ABA decreased markedly with the time of incubation. It was closely coincident with the increase of light- and exogenous GA_3-induced germination. It was also shown that the decrease of endogenous ABA content in Taiwan Red tomato seeds was not due to leakage to the medium, but to its catabolism. The initiation of ABA reduction by phytochrome and exogenous GA_3 requires a great deal of further study.