Leaf Photosynthesis and its Correlation with Leaf Area1

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Abstract
Comparisons among cultivars of leaf CO2 exchange rate (CER) based on leaf area may be confounded by leaf characteristics not usually accounted for in such comparisons. One such confounding characteristic appears to be leaf size. Correlation coefficients between leaf CER and leaf area (LA) were determined for genotypes of peanut (Arachis hypogaea L.), soybean [Glycine max (L.) Merr.], and sweet potato (Ipomoea batatas L.) and were compared with correlations for other crops reported in the literature. There were negative correlations between CER and LA in all crops examined. Significant negative correlations between LA and dark respiration were observed for wheat (Triticum sp.), alfalfa, (Medicago sativa L.), and peanut. Leaf area was negatively correlated with transpiration per unit LA and with leaf conductance for soybean. The relationship between leaf size and specific leaf weight was inconsistent in most crops. Comparisons of CER for genotypes having different leaf sizes may not represent the inherent differences in photosynthetic potential. Negative correlations between LA and CER may be one of the causes for the absence of consistent relationships between CER and yield.