Effect of light stress on growth and allelopathic activity of rice in southern Thailand

Global warming, such as rising temperature and lack of water, has effects on agriculture. Climate change can also reduce sunlight continuously for several months. This problem brings about this research to study the effect of light on growth and allelopathic activity of rice aiming at exuding allelochemicals to suppress weed growth for rice plants. Seven rice cultivars, i.e., Khao Dawk Mali 105, Phathum Thani 1, RD55, Chai Nat 1, Sang Yod Phatthalung, Leb Nok Pattani, and Cho Lung, were grown for three weeks. Two light intensities were used: 300 and 200 mu mol E/m2/s. Results showed that rice cultivars had effect on growth and allelopathic potential when tested with lettuce seedlings. Phathum Thani 1 rice cultivar had the lowest growth and the highest allelopathic potential when compared with other cultivars. Interestingly, rice cultivars that grew well, e.g., Leb Nok Pattani and Chai Nat 1, showed a low allelopathic potential. Rice plants receiving 200 mu mol E/m2/s of light grew better but had less allelopathic potential compared with those receiving 300 mu mol E/m2/s of light. This study expands the knowledge of rice allelopathy including the effect of physiological stress across rice cultivars and landraces.