Effects of elevated atmospheric carbon dioxide concentration and drought on soybean leaf photosynthesis
Soybean (Glycine max (L.) Merr. cv. Jack) was grown in the field in rain-protected plots to study effects of drought and atmospheric CO$\sb2$ enrichment on leaf gas exchange. Midday depressions in net leaf photosynthetic CO$\sb2$ exchange rates (Pn) were found in drought-stressed plants and the diurnal changes were mostly stomatal regulated, although accumulated drought stress eventually resulted in some non-stomatal limitations. However, seasonal changes in Pn were mostly limited by non-stomatal factors. Water use efficiency was always higher for drought stressed plants and depended on the severity of stress and associated stomatal or nonstomatal limitations. At enriched atmospheric CO$\sb2$ levels, stomatal limitations to Pn under drought stress were less important than at ambient atmospheric CO$\sb2$ levels. Morning and afternoon leaf starch levels were enhanced in both irrigated and nonirrigated plants in enriched CO$\sb2$. Afternoon starch levels were higher in stressed leaves than in non-stressed leaves at normal CO$\sb2$ levels.
Agriculture, Agronomy, Biology, Ecology, Biology, Plant Physiology
University of Illinois - Urbana-Champaign
Networked Digital Library of Theses and Dissertations
University of Illinois at Urbana-Champaign