Abstract

The aim of the study is to examine the relation of leaf senescence and its physiological characters at different flower internodes from flowering to maturing, to explore the aging mechanisms of adzuki bean leaf, to find out the intrinsic yield-forming mechanisms and to provide a theoretical basis for high-yield breeding and production of adzuki beans. A field experiment was conducted, the high-yielding (2000-75 and JiHong 9218) and the low-yield varieties (HongBao1 and WanXuan1), all adopted in the summer planting ecological region of China, were grown in 2008 and 2009, and their leaf physiological characters, such as chlorophyll contents, net photosynthetic rates (Pn), superoxide dismutase (SOD), catalase (CAT), peroxidase (POD) activities and malondialdehyde (MDA) contents were determined. The results indicated that the chlorophyll contents, P_n, SOD and CAT activities gradually decreased from 15 days after the varieties flowered to maturing, but their POD activities and MDA contents gradually increased when leaves senescence started. Leaf senescence initiated from the low internodes and gradually moved toward to the upper internodes after the plants flowered. Compared with low-yielding varieties, high-yielding varieties maintained higher contents of chlorophyll contents,P_n and SOD, CAT in the late stages, and thus resulting significantly higher grain yields. The overall data indicated that yield is positively correlated with leaf chlorophyll and P_n, as well as SOD and CAT activities and negatively associated with POD activities and MDA accumulations at the late growth stage. Therefore, effective inhibition of leaf senescence or prolonging the functional period of leaves at the late growing stage plays an important role in raising yield.

Key words: Adzuki bean, leaf senescence, chlorophyll content, seed yield.