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Varietal Comparison On The Responses Of Photosynthetic Rate And Leaf Water Balance At Different Soil Moisture Tensions In Rice.
Published 1985 · Biology
Differences in the photosynthetic activity and related leaf water balance were studied in eight rice varieties subjected to various levels of soil moisture tensions, i.e, flooded condition, values of 10, 20, 40 cbar and values at which leaf rolling began (50-62 cbar depending on the variety). The materials consisted of two lowland (IR 8 and Bosque), three tropical upland (Moroberekan, IAC 1246 and Batatais), two Japanese upland (Sensho and Rikuto Norin 24) and one dwarf mutant (Daikoku 1) varieties, respectively. The parameters observed were the photosynthetic rate (P), transpiration rate (T), leaf water potential (LWP), leaf diffusive conductance (1/r1) and leaf water content (W). The P decreased with the decrease in soil moisture with a concomitant decrease of T, LWP, 1/r1 and W, suggesting that the leaf water balance directly affects the P. Based on the responses of these parameters to soil-water stress, the material varieties were differentiated into four types. The lowland varieties performed high P and good leaf-water balance under fiooded condition. But they were very sensitive to the changes of the soil moisture, showing remarkable decreases of these parameters under moderate and severe drought. The tropical upland varieties showed rather low P under flooded condition, but they kept relatively good performance of P and leaf-water balance under moderate and severe drought conditions. The Japanese upland varieties showed intermediate values between the formers under flooded and moderate levels of the soil moisture tension (10-20 cbar), but under severe drought they showed sharp decrease of the values of these parameters as the lowland varieties did. The dwarf mu.tant Daikoku 1 performed comparatively high values of these parameters at every level of the soil moisture tension. The characteristics of these four types were discussed in view of their adaptation and plant-types.