银杏胚乳不同发育时期生理代谢变化与其胚性感受态的相关性研究

【目的】探究银杏胚乳发育时期生理变化与其胚性感受态之间的关系,筛选出高感受态的银杏胚乳外植体,为开展银杏体细胞胚发生的研究及建立银杏体胚发生体系提供支持。【方法】以6月10日—9月15日不同时间段的银杏胚乳为材料,研究各时间段银杏胚乳的抗氧化酶活性、可溶性蛋白、黄酮、内源激素含量变化及与其愈伤组织诱导率的相关性。【结果】银杏胚乳发育及其胚性感受态可以分为3个阶段:第1阶段为6月10日—6月30日,此时胚乳虽然细胞生理代谢旺盛,含水率和超氧化物歧化酶(SOD)活性较高,吲哚乙酸(IAA)与脱落酸(ABA)比值较高,易诱导愈伤组织,但其愈伤组织为松散易褐化的非胚性愈伤组织,胚性感受态水平较低。第2阶段为6月30日—8月10日,期间的胚乳抗性酶活性、黄酮含量、IAA与ABA比值都处于较低水平,而玉米素核苷(ZR)+异戊烯基腺苷(iPA)与ABA的比值处于较高水平;第3阶段为8月17日—9月15日,其胚乳可溶性蛋白含量以及过氧化物酶(POD)、过氧化氢酶(CAT)活性较高,黄酮含量达到峰值,IAA与ABA的比值处于较高水平,且ZR+iPA与ABA的比值处于较低水平,胚性感受态水平高,胚性愈伤组织发生率最高。第2阶段愈伤组织诱导率比第1和第3阶段都低,胚性感受态也较第3阶段低。【结论】3个不同阶段胚乳发育时期胚性感受态强弱和胚性愈伤组织诱导能力的排列顺序为第3阶段>第2阶段>第1阶段,7月20日—9月15日的胚乳胚性感受态较高,是诱导胚性愈伤组织较好的时期。

The relationship between physiological metabolism changes and embryogenic competence of endosperm in Ginkgo biloba at different developmental stages

【Objective】 In this study, high-embryogenic competence endosperm explants in Ginkgo biloba were screened out by investigating the relationship between the physiological changes in endosperm during different development periods and embryogenic callus induction. The results will provide supports for studying somatic embryogenesis and establishing a somatic embryogenesis system for G. biloba. 【Method】 Changes in antioxidant enzyme activities, flavonoids, and endogenous hormone content were measured, and embryogenic callus were induced using G. biloba endosperm as explants in eight stages (during June 10 to September 15). 【Result】 The endosperm development and embryogenic competence of G. biloba can be divided into three stages (Ⅰ-Ⅲ). The soluble protein and flavonoids content, peroxidase and catalaseenzyme activities, and indoleacetic acid (IAA) /abscisic acid (ABA) ratio in the endosperm of G. biloba all reached the highest levels; however, the (zeatin nucleoside (ZR) + isopentenyl pyrophosphate (iPA))/ABA ratio was lower than that at stage Ⅰ (during June 10 to June 30). Accordingly, the endosperm at this stage had high embryogenic competence and induction ability of embryogenic callus. Moreover, the endosperm had a high water content and superoxide dismutase (SOD) activity, and high IAA/ABA ratios, and it was also easy to induce callus; however, these induced callus were susceptible to loosening and easy browning, and the non-embryonic and embryogenic competence levels were lower at this stage. Stage Ⅱ lasted from June 30 to August 10. The three resistant enzyme activities, flavonoid content, and IAA/ABA ratios all exhibited low levels, while the (ZR+iPA)/ABA ratio was high. The callus induction rate was the lowest among the three stages, and the embryogenic competence level was lower than that at stage Ⅲ. 【Conclusion】 The embryogenic competence of G. biloba endosperm and embryogenic callus induction in the three stages of endosperm development was in the order stage Ⅲ > Ⅱ > Ⅰ. The optimum period of embryogenic competence in the endosperm explant was stage Ⅲ (August 17 to September 15) and the endosperm induced a high rate of embryogenic callus at this stage.