Changes in Leaf Rolling Rate of the Rice and Effect of Evaporative Condition.

Abstract

The diurnal change and change with the daily change of Leaf-rolling rate (LRR), and the effect of LRR on leaf water potential (LWP) under a high-temperature/low-humidity condition were examined. At noon, LRR of cv.C-115 and cv.Koshihikari was 45 and 5%, respectively, but LWP was nearly the same in both cultivars. This suggests that the difference in LRR between the two cultivars is not attributed to the difference in LWP. The daily mean LRR in the generally cultivated cultivar was near zero at the young seedling stage, and increased with plant growth. The strains that have a well-known rolled leaf gene, however, exhibited a high LRR at all developmental stages, and showed a diurnal change with the maximum value at noon. The daily change was related to the temperature and humidity, which are related to evaporation. A high LRR has been reported to suppress transpiration. In Koshihikari showing low LRR, neither LRR nor LWP was influenced by exposure to high-temperature / low-humidity condition, but in C-115 showing a high LRR, both LRR and LWP were increased by exposure to such conditions. These results suggest that LWP is affected by leaf-rolling. If we assume that a high LRR reflects the increase of boundary-layer resistance, the cultivars with a high LRR are considered to have a higher boundary-layer resistance and thus keep high LWP under high evaporative demand.