PJB-2022-481
EFFECTS OF SUBMERGENCE TIME, LIGHT, AND NITRATE COMPOUNDS ON SURVIVAL OF SOME MODERN RICE CULTIVARS UNDER FLOODED CONDITION
Pham Phuoc Nhan
Abstract
Under oxygen depletion, plants can use nitrate (NO3-) as the alternative terminal electron acceptor for anaerobic respiration; however, the effects of different nitrate solutions on improving rice survival in submergence conditions have received little attention. In this study, several popular rice cultivars in Mekong Delta, including OM4900, OM4218, OM6976, OM7347, IR50404, and IR64Sub1, have been submerged to evaluate their ability to survive under light and dark conditions. The influences of Ca(NO3)2, Mg(NO3)2, and AgNO3 supplement in combination with submergence on rice survival and growth or the concentration of soluble oxygen in solution were investigated. Among the cultivars, OM7347 was the best tolerant cultivar in darkness, with 83%, 38.67%, and 10.33% of seedlings surviving after 5, 10, and 15 days of submergence, respectively. Significantly, OM4900, OM4218, and IR64-Sub1 in light conditions was a higher survival rate than in darkness after 10-day submergence, most of over 70% on average. In dark conditions, an increase was observed in the total soluble sugar content in all treatments. During exposure to flooding stress, oxygen concentration gradually reduced over ten days of solution treatment. Applying Ca(NO3)2 and AgNO3 at 3 mg/L led to an increased survival rate for OM4900, OM4218, and IR64Sub1, considered sensitive, medium, and complete tolerant phenotypes, respectively. Overall, these nitrate compounds showed a positive effect on rice survival rate under complete submergence and could be considered as an alternative oxygen acceptor supply for rice seedlings' survival under anaerobic conditions and motivate further studies to explore nitrate's molecular mechanism in flooding stress.
Keywords: nitrate compounds, IR64Sub-1, modern rice, flooding stress
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