Temperature is one of the major factors which have a significant effect on plants. This study was carried out to investigate the effect of temperature variation on physio-biochemical characteristics of two rice cultivars i.e., Basmati385 and Xiangyaxiangzhan. A pot experiment with three different treatments of day-night temperature dynamics was carried out in a randomized complete block design with three replications. Treatments included T1: 33 °C/27 °C, T2: 27 °C/21 °C, T3: 21/15 °C under 1200X yellow light intensity and 75% humidity. Results revealed that increase in temperature enhances photosynthesis, the production of photosynthetic pigments, but such increment was higher in Xiangyaxiangzhan than in Basmati385. Furthermore, temperature variably affected protein synthesis, and the activities of enzymatic antioxidants viz., superoxide dismutase (SOD), peroxidases (POD), catalase (CAT) in both cultivars. Moreover, the highest yield was recorded at 27 °C/21 °C for both cultivars and the temperature of 27 °C/21 °C was regarded as the most suitable temperature at filling stage for rice compared with 33 °C/27 °C and 21/15 °C.

Selenium (Se), as an essential element, has its effects on the growth and development of plants. Present study aimed to assess Se mediated chlorophyll contents, net photosynthesis, biomass accumulation and activity of carbon metabolism enzymes. Three different levels of Ethylenediamine tetra acetic acid -chelating Se (EDTA-Se) at 10(E1), 30(E2) and 50(E3) μmol L -1 were overhead applied at initial heading stage of two aromatic rice cultivars i.e., Xiangyaxiangzhan and Meixiangzhan2, the treatment without Se were served as control (CK). Results revealed that exogenous Se applications enhanced the chlorophyll content as well as net photosynthetic rate (Pn), meanwhile, grain weight at maturity and the biomass accumulation during the filling had been remarkably improved. Furthermore, growth, yield and quality components were also improved by Se application. Hence, Se proved better for both rice cultivars whereas the E2 was the best treatment with the highest yield, biomass accumulation and net photosynthesis rate.