Effects of Water Stress under Contrasting Environmental Conditions on Transpiration and Photosynthesis in Soybean

Publisher Website
Google Scholar
Abstract
Continuous and simultaneous measurements of CO2 exchange and transpiration rates of whole soybean plants were made under contrasting, controlled environmental conditions when water stress was imposed by withholding water. Daytime temperatures and vapour pressure deficits were 27.5 ° C/12 mbar; 27.5 ° C/5 mbar; 22.5 ° C/12 mbar, and 22.5 ° C/5 mbar. The experimental conditions were virtually the same as the conditions under which the plants had been grown. Under all four treatments photosynthesis and transpiration rates were closely correlated as water stress increased, but in view of the evidence for a significant mesophyll resistance to photosynthesis in- both stressed and unstressed plants it is not considered that this is due to total stomatal control. At — 0.4 bar soil water potential (ψsoll) the rates of transpiration and photosynthesis became independent of the atmospheric conditions and were very similar under all treatments. This is attributed to slow movement of water into the root zone from the surrounding soil with associated stomatal closure limiting the rates of water uptake and transpiration. With decreasing ψsoll, relative water content of the leaf (RWC) fell more rapidly and to lower levels under 27.5 ° C/12 mbar conditions than under the other treatments. The least reduction in RWC was under the 22.5 ° C/5 mbar treatment. Increasing soil water stress had the greatest relative effect on rates of gaseous exchange under 27.5 ° C/12mbar conditions and least under 22.5 ° C/5mbar conditions.
Keywords

This publication has 0 references indexed in Scilit: