EFFECTS OF ELEVATED OZONE CONCENTRATIONS ON THAI JASMINE RICE CULTIVARS (ORYZA SATIVA L.)

摘要

This study investigated the effects of O_3 on growth, yields and physiological characteristics of Thai Jasmine rice cultivars. Rice was exposed to O_3 for 7 h day~(-1) in a closed chamber for 113 days, beginning from seedling until harvest. O_3 concentration in each chambers was controlled at 0 ppb, 50 ppb, 100 ppb, 150 ppb and at the ambient level. Effects of O_3 on leaf area index (LAI) became obvious at maturity when LAI significantly decreased in the treatments under elevated O_3 concentrations. Results in shoot biomass indicated that shoot length was more affected by O_3 than shoot dry weight. Root length rather than dry weight was significantly reduced in all cultivars. The most severe damage of O_3 was found in photosynthetic components, namely chlorophyll and carotenoid contents, and rate of net photosynthesis. Yield components were also strongly affected by O_3. The highest reduction in filled seed per ear was found in the Pathumthani 1 cultivar by 78% when it was exposed to 150 ppb O_3 compared to the control (0 ppb). Similarly, 100-grain weight was also reduced as much as 12.3% in this cultivar.