Changes in water content of rice grain during water deficit
1994
Namuco, O.S. | Ingram, K.T. (International Rice Research Inst., Los Banos, Laguna (Philippines))
Results showed that grain dry weight increased after panicle emergence regardless of water deficit; only slight differences in rates, however, were observed among most of the cultivars. During the panicle emergence period of 10-14 d before maximum water deficit, AUS257, a small-seeded cultivar, increased grain dry weight by 0.8 mg/d while IRAT104, a large-seeded cultivar, increased its grain dry weight by 2.4 mg/d. Except for AUS257, water content was almost constant until 5-6 d after panicle emergence, after which it decreased almost linearly. At harvest, grain water content ranged from 10 to 30 percent. Rice grain lost less water when panicle emergence was close to maximum water deficit than when panicles emerged between 15 and 19 d before maximum water deficit (grain lost 2.5 percent water/d). IRAT104 lost 4.2 percent water/d compared with AUS257, which lost only 3.3 percent water/d, even though their panicles emerged within the same period. Grain water content and grain dry weight were negatively correlated. The leveling off in dry weight was not accompanied by leveling off in water content because water loss continued for a few more days. These findings suggest that even if grain is fully mature, it continues to lose water even under water deficit. Results also suggest that a decrease in water loss in the grain was due to the low water status during water deficit and not mainly to maturation
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