Sustaining rice agriculture through physiological profiling of rice cultivars for salt tolerance
2008
Dionisio-Sese, M.L.
Saline soils are widespread globally and constitute a serious threat to the sustainability of rice production. The complex nature of salt stress and the wide range of plat responses necessitate the full understanding of the physiological mechanisms underlying salt tolerance. Salinization of contrasting rice cultivars at the seedling stage resulted in the following physiological profile of rice cultivars tolerant to salt stress: a) low shoot Ma+ content, b) low shoot Na+: K+ ratio, c) stable or high superoxide dismutase activity, d) low electrolyte leakage rate, e) lesser decline in photosynthesis rate, f) low non-photochemical quenching, g) less decline in stomatal conductance with long-term salt exposure, h) low stomatal conductance at onset of salt stress, i) low transpiration rate at salt onset, and j) high root abscisic acid content at the start of salinization. These characters, alone or in combination, resulted in the plant display of tolerant phenotypic characters such as a) constant growth rate, b) low visual score signifying less damage, c) high percentage survival, d) high green leaf area, and e) low reduction in root and shoot biomass upon salinization. Employing these characters would help plant breeders in the selection of criteria or indicators for salt tolerance as well as open the avenue for genetic engineering of rice plants with enhanced salt tolerance.
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