Abstract:

【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.

Key words: Pachira macrocarpa, seed deveopment, soluble sugar, desiccation tolerance