Diurnal patterns of soybean leaf inclination angles and azimuthal orientation under different levels of ultraviolet-B radiation

This paper documents the diurnal pattern of heliotropic leaf movements for four different soybean (Glycine max) cultivars and its relationship to increased ambient levels of ultraviolet-B radiation. Considerable variation in diurnal patterns of leaf movement within and among cultivars was found, but no effect of the level of UV-B radiation was observed. The ranking of the four cultivars in order of decreasing sensitivity to UV-B radiation was the same as a ranking based on midday leaf inclination, with tolerant cultivars displaying steeper leaf angles, Plants that have the ability to reduce light interception at midday, thereby reducing light and temperature stress effects, may be better prepared to cope with the additional effects of UV-B radiation on photosynthesis, stomatal conductance, plant morphology, and growth.