Abstract
A quick estimation of canopy light extinction coefficient (k) is necessary for simultaneous evaluation of the traits related to light reception in many kinds of plant populations and for the selection in breeding programs. We examined whether the inclination angle from the horizon of leaf, which forms a canopy, can be used for a quick estimation of k by using two indica varieties, Takanari and Milyang 23 and three japonica varieties, Koshihikari, Aikoku and Sekitori. We clarified that the average inclination angle of leaf blades of a hill can be estimated from the measurement of leaves on the main stem alone. Varietal differences in the inclination angle of leaf blade and k were observed clearly after the heading stage through the ripening stage. There was a close linear relationship between the inclination angle of leaf blade and k through all varieties at the heading stage. The inclination angle decreased after heading, and it was prominent in Koshihikari, Aikoku and Sekitori. The coefficient k increased in the middle ripening stage not only in Koshihikari, Aikoku and Sekitori, but also in Takanari. In Takanari with a larger and heavier panicle, k increased significantly at the ripening stage even though the leaf inclination angle was kept large. We concluded that the difference in k among varieties could be estimated from the inclination angle of the leaf blade at heading, but not at the ripening stage when panicles had a large inclination angle, especially in the varieties with heavy panicles.
