No abstract

Selenium (Se) is an essential element to humans, animals and plants, but little is known about roles of Se in yield and antioxidant enzyme activities of rice. In this study, sodium selenate with 10 (T1), 30 (T2) and 50 (T3) μmol L -1 concentrations and distilled water (CK) were sprayed onto rice cultivars, or more precisely Meixiangzhan-2 at rupturing stage during the experiments in South China, 2017. Treatments were arranged in a split-plot design with three replications. The result showed that spraying 10, 30 and 50 μmol L -1 sodium selenate at rupturing stage could improve the activities of oxidant enzymes such as peroxidase (POD), superoxide (SOD) and catalase (CAT) and lower the malonaldehyde (MDA) concentrations at filling stage. Furthermore, Se applications could enhance the chlorophyll content at middle and late phase of filling stage and grain yield at maturity. Therefore, Se applications could alleviate the detrimental effects of rice leaf senescence by regulating the activity of enzymatic antioxidants and also increasing chlorophyll content at the filling stage which will be helpful to sustain growth and yield formation in rice production.

Transplant density is an important factor which has impacts on rice growth and development in transplanted rice production system. Present study used three transplant densities in paddy field experiment and set as D1 (transplant spacing of 20 cm × 24 cm, about 2.085 hundred thousand hills for each hectare), D2 (transplant spacing of 20 cm × 20 cm, about 2.603 hundred thousand hills for each hectare) and D3 (transplant spacing of 20 cm × 16 cm, about 3.120 hundred thousand hills for each hectare). The results showed that high density (D3) not only reduced the net photosynthetic rate and LAI values at heading stage, but also decreased dry matter accumulation and transportation compared to D1 density. The highest yield was recorded in D1 density and the lowest yield was recorded in D3 density. Study also revealed that high density caused yield loss by decreasing the grain number and seed-setting rate. Furthermore, high density also increased chalk rice rate and chalkiness while reducing the amylose content. The activity of sucrose synthase (SS) in D3 was significantly lower than D1 and it might relate to the reduction of grain quality.