Relationships among Specific Leaf Weight, Photosynthetic Rate, and Seed Yield in Soybean

Abstract

Increasing leaf apparent photosynthesis (AP) may improve seed yield in soybean [Glycine max (L.) Merr.]. Selection for high specific leaf weight (SLW) may increase AP. The objectives of this study were to (i) incorporate extremes in SLW from exotic germplasm into adapted soybean lines with high agronomic potential, (ii) compare the time course of SLW in lines known to vary in SLW, and (iii) evaluate the relationships among SLW, AP, and seed yield. In 1991 and 1992, 16 genotypes representing extremes in SLW were grown at Urbana, IL, and West Lafayette, IN. The SLW and AP were measured at the R2, R4, and R5 growth stages. At the R5 growth stage in 1992, AP was also measured at approximately twice ambient CO2 concentrations. A subset of lines was sampled weekly for SLW from R1 until R7. High SLW lines displayed a greater rate of increase in SLW than low SLW lines beginning after R2 and continuing until R6. Significant class mean differences (P < 0.01) in SLW were observed on all sample dates across locations. Class mean differences in AP at ambient and twice ambient CO2 concentrations were observed at Urbana, although ranking of SLW classes was inconsistent across years. Leaf rugosity was negatively correlated with AP and seed yield. A high SLW line with low rugosity, LG89‐1917, expressed high AP and produced yields very similar to the adapted cultivars Chapman and Elgin 87. Lines with high SLW and low leaf rugosity may hold the greatest potential for high AP and yield improvement.