Effects of shading at seedling stage on photosynthetic characteristics of Arachis hypogaea L. leaves

The photosynthetic characteristics of a peanut variety, Huayu 22, under shading treatments (50%, 85%) and subsequent recovery under full light were studied at seedling stage in the field. The shading treatments were last 40d. Relative to those under full light, the peanuts grew in shading environment had lower net photosynthetic rate (P_n), the light compensation point (LCP), the carboxylation efficiency (CE), the non-photochemical quenching (NPQ), higher apparent quantum yield (AQY), maximal photochemical efficiency (F _v/F_m) and the content of total chlorophyll content. It shows that peanut has self-adjusting and adaptation ability to low light stress. When exposed to strong light at noon, F_v/F_m, which can reflect the efficiency of PS II, decreased obviously in both shading seedling leaves and full light seedling leaves. In all treatments, Photoinhibition was more severe in lower light treatment seedlings. Otherwise, when removed shading stress, F_v/F_m and Pnof peanut seedling leaves continued to decrease in 5d relative to those of the control under lull light, and began to increase subsequently. F_v/F_m and P_n of 50% shading seedlings recovered to the same level as the control in 8d and lOd, respectively; however, F_v/F_m and P_n of 85% shading seedlings reached the top values in 15d and 20d, respectively, whereas P_n was still lower than that of the control.