Changes Of Endogenous Hormone ABA Contnet,Antioxidant Enzyme Activities And Seed Quality During Seed Development In Sponge Gourd

Seed development starts from the double fertilizations in the embryo sac. Seed development of higher plant was divided into three stages:morphogenesis, reserve accumulation and maturation drying. After the three stages, a seed has the ability to germinating in the suitable environment. However, there are no detailed information of seed development in sponge gourd. In the study, seed developments of two single-cross hybrids of sponge gourd (cv. Zheda2and Zheda3) were used by harvesting seeds at different stages of maturation. Changes in abscisic acid content, antioxidant enzyme activities and seed quality during seed development and maturation of sponge gourd were studied. Main results were achieved as follows:1. In this study, a high performance liquid chromatographic (HPLC) method was developed for isolation and determination of plant hormone abscisic acid (ABA) in seeds of sponge gourd. A reverse phase C18column was used, and the optimal parameters were5:5methanol to water with0.2%phosphoric acid as mobile phase, column temperature35℃and flow rate0.8ml/min. UV detection at260nm was used for ABA determination. Sample processing of chromatographic analysis was as follows:the extraction of endogenous ABA by acetonitrile, then concentrating with nitrogen gas blowing, the eliminating of lipids by freezing lipid filtration, final extracting by ethylacetate, and the sample was subsequently analyzed by HPLC. The results showed that the limit of ABA detection was0.01mg/L, average recovery rate was80.53%. It suggested that present method with reliable and rapid traits can be used for accurate separation and determination of endogenous ABA in seeds of sponge gourd.2. Changes of the ABA levels and antioxidant enzyme activities in both fresh and dry seeds were detected. The results showed that desiccation tolerance were acquired during the stage of reserve accumulation. ABA content was high in the second stage of seed development and then declined during the stage of maturation drying. ABA content alone may not accurately reflect ABA action. Artificial drying increased antioxidant enzyme activities during seed development. 3. Changes in seed quality were detected during seed development and maturation in two single-cross hybrids of sponge gourd in the experiment. A number of different tests (standard germination, electrical conductivity, cold test and accelerated aging test) were utilized to evaluate seed quality of serially harvested seed lots. The optimal harvesting time was56-63days after pollination (DAP). Zheda2and Zheda3aquired maximum seed dry weight at49DAP and42DAP, respectively, while maximum seed quality was attained at56DAP for Zheda2and49DAP for Zheda3. Maximum seed quality was occurred7d after maximum dry weight. The melanin content in seed coats was measured in the experiment as well, which had a close relation with the ability of seed germination and can be used as a harvest indicator in the seed production of sponge gourd.