[Effects of phytase Q9 on the yield and senescence characteristics of summer maize shaded in the field]

Light shortage in the canopy of summer maize resulted from the decrease of solar radiation and the increase of planting density in Huanghuaihai region could reduce maize yield. In order to explore the effects of phytase Q9 on leaf senescence characteristics of summer maize, three sha-ding treatments with summer maize hybrid 'Denghai 605' (DH605) were conducted, including shading at flowering to maturity stage (S₁), shading at ear stage (S₂), and shading at whole growth stage (S₃) with natural lighting in the field as control (CK). Chemical control reagent phytase Q9 was used to regulate the shading treatments (the original solution was diluted by 100 times) and the CK exogenously, namely shading at flowering to maturity stage-phytase Q9 (S₁Q), shading at ear stage-phytase Q9 (S₂Q), and shading at whole growth stage-phytase Q9 (S₃Q), and natural lighting-phytase Q9 (CKQ), with spraying water at the same stage as the control. The results showed that leaf area index (LAI), soil-plant analysis development (SPAD) value and net photosynthetic rate of summer maize was significantly reduced by shading, which led to decreases of yield. The activities of superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT) in ear-leaf decreased. The content of malondialdehyde (MDA) and free proline increased, and that of soluble protein decreased. The spraying phytase Q9 significantly increased LAI, SPAD and net photosynthetic rate in S₃Q and S₂Q. MDA and free proline content in S₃Q, S₂Q, and S₁Q were significantly decreased, and soluble protein content and POD activity was significantly increased. SOD and CAT activities in S₂Q and S₃Q were significantly increased. The yield of S₃Q, S₂Q and S₁Q were 19%, 8% and 7% higher than that of S₃, S₂ and S₁ respectively. There was no significant difference between CKQ and CK. In conclusion, phytase Q9 could effectively alleviate the negative impact of low light on yield formation of summer maize, and increase grain yield by improving photosynthetic capacity of leaves and delaying leaf senescence.