A Study On The Mechanism Of Waterlogging Tolerance In Annual Wild Soybean (Glycine Soja)

Compared to the environment of any other areas of china, the one of south china is knewn for its great precipitation, clay soil and hight ground water level, which prevent many legume forages species from satisfactory growth and yields. So, in order to promote sustainable and productive stockbreeding. It is urgent to introduce some forages species adaptable to the environment of south china. One of many promising legume forage species is annual wild soybean, a productive grass whose ecotypes can be found all over the china and eastern part of East Asia, these ecotypes respond physiologically and morphologically to flooding condition in regard to their waterlogging tolerance.In order to investigate the mechanism of waterlogging tolerance of annual wild soybean, an anatomical observation on development of root and stem and flooding effect on it were carried out with the materials collected from the Yuantuojiao beach in Yinyang town, Qidong city, Jiangsu province and hillside of Baohua Mountain in Jurong county of Jiangsu province, and delta of Yellow River in Dongyin city, Shandong province.The results indicated that annual wild soybean began forming the cortex aerenchyma at 3-5 weeks after sowing, and then the aerenchyma developed completely from root to stem after 2 weeks. The aerenchyma of annual wild soybean firstly formed at the position near root collar, and then it extended to root tip and stem. The time of aerenchyma formation differed within the materials.The results of flooding experiment showed that flooding promoted the formation of cortex aerenchyma in annual wild soybean. The proportions of cortex aerenchyma accounting for transverse section and sporosity were noticeably higher than those of the control group in wild soybean from Qidong and delta of yellow river (P<0.05) after flooding for 1, 2, 3 weeks respectively. The sections of hypocotyls also showed that air spaces of treatment group were more than those of the control group. The changing of cortex aerenchyma in Jurong wild soybean was not remarkable after flooding for 1 week. There was no significant difference between treatment group and control group in proportion of cortex aerenchyma accounting for transverse section and sporosity for 1 week flooding. Flooding for 2, 3 weeks respectively, the formation of cortex aerenchyma was promoted.Flooding for 2 weeks was good for cortex aerenchyma to develop by comparing the effects of different durations of flooding on the formation of cortex aerenchyma. The difference of root activity between treatment and control group was not significant (P>0.05).Flooding at the 3rd or 4th week after sowing was optimum to promote the formation of cortex aerenchyma. Sporosity of wild soybeans flooded at the 3rd or 4th week after sowing was significantly higher than those of the control group and their aerial part grew as well.Annual wild soybean may not have waterlogging tolerance before the formation of cortex aerenchyma in root. The seedling of annual wild soybean that formed cortex aerenchyma at the 3rd or 4th week after sowing possessed high waterlogging tolerance. When cortex aerenchyma began to form, flooding was beneficial to its formation, which could enhance the waterlogging tolerance of annual wild soybean.