Leaf Conductance in Japonica and Indica Rice Varieties : I. Size, frequency, and aperture of stomata

Abstract

Varietal differences in leaf conductance were studied in field conditions using 51 rice varieties, including japonica, indica, and japonica-indica hybrid. Leaf conductance of indica and japonica-indica hybrid was clearly larger than that of japonica at panicle formation stage. Cuticular conductance was much lower as compared to leaf conductance, indicating the stomata is the major path of water loss. Thus, we measured size, frequency, and aperture of stomata, and evaluated the relative importance of these factors to leaf conductance. Only slight differences were observed in length of the pore and the guard cells of stoma among rice varieties. By contrast, stomatal frequency of japonica-indica hybrid and semidwarf indica was clearly higher than that of japonica and tall indica. In addition, stomatal aperture of indica and japonica-indica hybrid was remarkably larger than that of japonica. Analysis of relative importance of frequency and aperture of stomata to leaf conductance showed that the leaf conductance was strongly affected by stomatal aperture, whereas it was slightly influenced by stomatal frequency in rice. It is concluded that the stomatal aperture is the major factor which causes the difference of leaf conductance between japonica and indica or japonica-indica hybrid.