马拉巴栗种子发育中可溶性糖变化与种子脱水耐性的关系

 【目的】探索马拉巴栗种子在发育过程中脱水耐性的形成与可溶性糖之间的关系。【方法】以不同发育阶段的马拉巴栗种子和离体胚为试材,观测种子发育过程中可溶性糖组分和含量以及种子和离体胚的脱水耐性变化。【结果】开花后30～70 d是种子最快膨胀期,花后50 d开始形成脱水耐性,50～70 d种子脱水耐性逐渐增强,70 d种子脱水耐性最强,80 d脱水耐性转而下降,完全成熟时（90 d）再轻微上升,其脱水耐性的强弱顺序为：70 d＞90 d＞80 d＞60 d＞50 d,离体胚的脱水耐性与种子的情况相似,其脱水耐性顺序为：70 d＞80 d＞90 d＞60 d＞50 d＞40 d。在种子发育过程中,初期果糖、半乳糖、葡萄糖含量较高,随后呈下降趋势,蔗糖和麦芽糖含量从开花40 d后急剧增加,寡糖（棉籽糖和水苏糖）在花后50 d形成,并一直保持较高含量,其中,蔗糖和水苏糖含量最高值出现在开花后70 d。在种子发育中,还原性糖与非还原性糖的比例一直下降,90 d时两者比值达到最低,此时寡糖含量也略有下降,寡糖/蔗糖比值达到最高,推测80 d后种子可能由发育状态转入萌发状态。【结论】马拉巴栗种子脱水耐性与种子发育时期有关,棉籽糖和水苏糖是影响种子脱水耐性形成的重要因子,种子脱水耐性强弱与棉籽糖和水苏糖等非还原性糖的含量及还原性糖/非还原性糖比值密切关联。

Relationship Between Dehydration Tolerance and Soluble Sugars During Seed Development of Pachira macrocarpa

【Objective】 This work was aimed to investigate the relationships between dehydration tolerance and the composition and concentrations of soluble sugars during seed development of Pachira macrocarpa. 【Method】 Whole seeds or isolated embryos of P. macrocarpa at different developmental stages were used to investigate the changes of soluble sugar composition and concentration and their relationships with dehydration tolerance. 【Result】 The results showed that seed developed rapidly at 30-70 days after anthesis (DAA). Dehydration tolerance started to develop at 50 DAA and continue to increase until 70 DAA. when it reached the highest dehydration tolerance. Dehydration tolerance started to decline at 80 DAA but increased slightly at 90 DAA when seed are fully matured. The order of seed dehydration tolerance is 70 DAA＞90 DAA＞80 DAA＞60 DAA＞50 DAA. The dehydration tolerance of isolated embryo exhibited a similar pattern with the order of dehydration tolerance being 70 DAA＞80 DAA＞90 DAA＞60 DAA＞50 DAA＞40 DAA. The main soluble sugars in early developing P. macrocarpa seeds were fructose, galactose and glucose. When seeds turned more mature, sucrose and maltose became dominant in soluble sugars from 40 DAA, raffinose and stachyose started to accumulate from 50 DAA and kept at high concentrations in the seed. The highest concentrations for sucrose and stachyose in seeds were observed 70 DAA. The ratio of reducing sugars to non-reducing sugars reached the lowest after 90 DAA, while the ratio of oligosaccharide to sucrose reached the highest. It is presumed that seeds switched to germination state from developmental state 80 DAA. 【Conclusion】 These results above suggested that there is a highly correlation between dehydration tolerance and development of P. macrocarpa seeds. Raffinose and stachyose are important facts for the formation of dehydration tolerance of P. macrocarpa seeds. The dehydration tolerance of the seeds are in close relationship with the content of the non-reducing sugars like the raffinose and stachyose, and the ratio of reducing sugars to non-reducing sugars.