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Varietal Differences in Net Photosynthesis of Soybean Leaves 1
Author(s) -
Dornhoff Gary M.,
Shibles R. M.
Publication year - 1970
Publication title -
crop science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.76
H-Index - 147
eISSN - 1435-0653
pISSN - 0011-183X
DOI - 10.2135/cropsci1970.0011183x001000010016x
Subject(s) - photosynthesis , biology , stomatal density , dry weight , botany , agronomy , horticulture
Leaf net CO 2 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 CO 2 . Both stomatal resistance and mesophyll resistance to diffusion of CO 2 were different among genotypes. No genotypic differences were found in CO 2 evolution into CO 2 ‐free air in light, or in CO 2 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 CO 2 diffusion resistance within the leaf, and/or (b) increased demandfo r photosynthate for seed formation.