Variation of leaf rolling and its physiological significance under soil water-limiting conditions in rice

摘要

Leaf rolling was investigated in rice using 143 cultivars, including indica and temperate and tropical japonica types, grown under low and upland conditions. Leaf rolling was measured with a ruler as the leaf rolling rate (LRR): LRR (%) = (1-width of the rolling leaf/width of the flattened leaf)X100. When leaves rolled to the abaxial side, LRRs were given minus values. Ranges of LRR in both conditions were 22.1 to -23.1% and 24.7 to -19.5%, respectively. Effects of the upland condition on LRR differed among rice ecotypes. Under upland conditions, leaves of the japonica type rolled more adaxially and those of indica and Japanese upland cultivars rolled more abaxially than under lowland conditions. The greater the LRR, the lower the values of photosynthesis, transpiration and stomatal conductance. However, the degrees of these declines differed depending on whether the leaves rolled adaxially or abaxially. Cultivars whose leaves rolled abaxially showed slower decline than cultivars whose leaves rolled adaxially. These findings may suggest that in those leaves rolling abaxially, transpiration was maintained by the decreased boundary layer resistance, and the leaves were kept nearly flat after the commencement of wilting so as not to restrict carbondioxide exchange.