Differences between two spring wheat cultivars in effects of shadings on dry matter production

This study investigated the effects of shadings (by a cloth with 70% interception) before and after anthesis on dry matter production in a field condition for two spring wheat cultivars whose canopy structures are different. Grain yields were decreased 32-34% by shadings in Norin 61, though only 13-15% by shadings in Haruyutaka. These were mainly caused by decreases with shadings in total dry weight, which accounted for 27-32% in Norin 61 and 11-13% in Haruyutaka. It was found that Haruyutaka difinitely showed less decrease in dry matter production in response to a shortage of solar radiation than Norin 61 did. The nitrogen contents in the second and third leaves at the milli ripe stage were increased by shading before anthesis in Haruyutaka, but not in Norin 61. Furthermore, the daily increases of water soluble carbohydrate in leaves were increased by shading after anthesis in Haruyutaka and decreased by shading in Norin 61. These results suggest that the photosynthesis in a canopy was enhanced after shadings in Haruyutaka, but not in Norin 61.