Leaf Senescence and Reactive Oxygen Metabolism in Different Adzuki Bean Cultivars (Lines)

To examine the relation of leaf senescence and its reactive oxygen metabolites from different nodes of various adzuki bean cultivars, to explore the aging mechanisms of adzuki bean leaf, to find out the intrinsic yield-forming mechanisms and to pro-vide a theoretical basis for high-yield breeding and production of adzuki beans. We conducted a field experiment, two high-yielding cultivars, 2000-75 and Jihong 9218, and two low-yielding cultivars, Hongbao 1 and Wanxuan 1, all adopted in the summer planting ecological region of China, were grown in 2008 and their leaf physiological indices, such as chlorophyll content, soluble-protein content, SOD, CAT and POD activities and MDA accumulations, were measured from flowering to ripening stages. The results showed that after flowering of the cultivars, their functional leaves aged gradually from bottom nodes to top nodes, and showed de-creased chlorophyll and soluble-protein contents, decreased SOD and CAT activities and increased POD activities and MDA accumulations in the proceed of senescence, for which there were significant differences among cultivars. Compared with the low-yielding varieties, the leaves of the high-yielding cultivars aged slower, showing relatively higher contents of chlorophyll and soluble-protein, higher activities of SOD and CAT at the late growth stage, and thus resulting significantly higher grain yields. The overall data indicated that yield is positively correlated with leaf chlorophyll and soluble-protein contents, as well as SOD and CAT activities and negatively associated with POD activities and MDA accumulations at the late growth stage. Therefore, effective inhibi-tion of leaf senescence or prolonging the functional period of leaves at the late growing stage plays an important role in raising yield.