Responses of gas exchange and phototropic leaf orientation in soybean to soil water availability, leaf water potential, air temperature, and photosynthetic photon flux
Journal
Environmental and Experimental Botany
Journal Volume
32
Journal Issue
2
Pages
153-161
Date Issued
1992
Author(s)
Abstract
The response of rapid, tropic leaf movement and gas exchange to long- and short-term environmental factors in potted soybean (Glycine max cv. Cumberland) was examined. Leaf angles measured on leaves of droughted plants under a vertical illumination were steeper relative to those of well-watered plants, resulting in a negative linear relationship between steady-state leaf angle and leaf water potential. Short-term changes in leaf water potential induced by root cooling and rewatering did not affect the steady-state leaf angle in response to vertical illumination. Though photosynthesis and stomatal conductance responded to short-term changes in leaf water potential, a carryover effect of long-term water availability on intercellular CO2 concentration was still present. Increasing photosynthetic photon flux and air temperature increased steady-state leaf angle at a given leaf water potential. However, leaf movements of droughted plants were more sensitive to increasing photosynthetic photon flux and air temperature relative to those of well-watered plants. Leaves of droughted plants had a reduction in photosaturated photosynthesis and the photon flux required to saturate photosynthesis compared to leaves of well-watered plants. The thermal optimum for photosynthesis was also shifted to a lower leaf temperature in leaves of droughted plants. The only factors affecting rapid, reversible tropic leaf movements over the short-term (minutes) appeared to be light and temperature, while leaf water potential had its major effect over a long-term scale (days-weeks). Additionally, the response of paraheliotropic leaf movement to short-term changes of environmental variables was complementary to responses of carbon dioxide and water vapor gas exchange to long-term environmental factors. © 1992.
SDGs
Type
journal article