Leaf Senescence And Physiological Characteristics In Different Adzuki Bean Cultivars (Lines)

Adzuki bean has been even considered as a medical crop, due to its ability to relive some medical conditions. Rich in nutrition, adzuki bean has been offering a great benefit to Chinese people. Because of recent changes of food composition and health concerns in China, adzuki bean, as a medicinal and nutritious crop, is attracting more attentions in agricultural practice. However, as an annual herbage plant, adzuki bean has been grown in a small scale in the country, due to its low-yield. Systemic researches have not been reported in its physiological and biological properties. In order to increase the yield of this crop, the studies on adzuki bean are essential, especially in ecological and biological behaviors of the plant after flowering, which may play a important role in its yield and quality. As a result, the field observations on adzuki bean need some appropriate indexes and criteria to illustrate the relationships between plant behaviors and productivity. The achievements from these studies may lead to a significant improvement of field managements and farming practices. Therefore, it has become an urgent issue and needs to be addressed quickly, in order to increase the yield and quality of adzuki bean in agricultural plantation.The objectives of this study are to investigate aging properties of the leaves of adzuki beans, to evaluate the relationships of leaf senescence and reactive oxygen metabolites from different nodes of four adzuki bean cultivars, and to discuss theoretical basis for high-yield breeding and formation of adzuki beans. This study was carried out on two high-yielding cultivars,2000-75 and Jihong 9218, and two low-yielding ones,Hongbao 1 and Wanxuan 1.(1) Leaf physiological indices, such as chlorophyll content, soluble-protein content, net photosynthetic rate (Pn), transpiration rates(Tr),stomatal conductance(Gs) were monitored from flowering to ripening stages. The observations indicated that Pn,Tr,Gs,Chl and SP of leaves on the main stems at the flowering nodes declined from the flowering to ripening stage. The photosynthetic capabilities of the leaves decreased in an order from Leaf 8,7,6 to 5 at the same growth stages. Significant differences were noticed in leaf photosynthetic capabilities of these adzuki beans. The net photosynthetic rates of high-yield cultivar were greater than that of low-yield ones. The high-yield cultivars were able to keep a relatively high photosynthetic capability at the late stage of growth. The functional leaves of high-yield cultivars aged slowly in an order from the bottom to the top nodes of the plants after flowering.(2)After adzuki bean flowering, CAT,SOD activity had a closely relationship with leaf senescence. Sufficient CAT,SOD activity prevented the damages on leaf membrane structures and physiological capability, and prolonged the functional duration of leaves and life-phase of the plants in the field. Because that POD activity and MDA are products of lipid peroxidation, the content of POD,MDA is an indicator of damage in the membrane structures and physiological capability. at the late growth stage. Agriculture practice should be directed to low the level of POD,MDA contents.(3)From flowering to ripening stages, root vigor had a closely relationship with leaf senescence. The observations indicated that root vigor of adzuki bean at the flowering nodes declined, The root vigor of high-yield cultivar were greater than that of low-yield ones.