HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Dornhoff, G. M. Articles by Shibles, R. M. Search for Related Content PubMed Articles by Dornhoff, G. M. Articles by Shibles, R. M. Agricola Articles by Dornhoff, G. M. Articles by Shibles, R. M.

Varietal Differences in Net Photosynthesis of Soybean Leaves¹

Leaf net CO₂ exchange of 20 varieties of soybeans (Glycine max (L.) Merr.) was measured by infrared gas analysis. The varieties differed significantly in net photosynthesis at 100, 200, 300, and 400 ppm CO₂. Both stomatal resistance and mesophyll resistance to diffusion of CO₂ were different among genotypes. No genotypic differences were found in CO₂ evolution into CO₂-free air in light, or in CO₂ compensation concentration. Density-thickness (leaf weight to leaf area ratio), on both dry- and fresh-weight bases, was highly correlated with net photosynthesis. The evidence suggests that varietal differences in net photosynthesis were mainly a result of differences in diffusive resistances.

Net photosynthesis of most varieties began to increase around Aug. 4, at the approximate beginning of seed filling. A linear trend in increasing leaf density-thickness occurred from beginning of testing. The increase in net photosynthesis is postulated a result of (a) decreased CO₂ diffusion resistance within the leaf, and/or (b) increased demandfo r photosynthate for seed formation.

Key Words: Glycine max • Diffusive resistances • Leaf density-thickness • Specific leaf weight

² Graduate Assistant and Professor, Department of Agronomy, Iowa State University, Ames, Iowa 50010.

Received for publication June 30, 1969.