Genotypic variation in carbon exchange rate, functional leaf area and productivity in finger millet (Eleusine coracana gaertn.): An approach to identify desirable plant types for higher water use efficiency under rainfed conditions

Abstract

Abstract Earlier field studies in finger millet showed the lack of a direct relationship between the leaf area duration and the grain productivity and biomass production of finger millet under rainfed conditions, indicating that there are genotypes with high productivity in spite of a low assimilation leaf area. In this study, an attempt was made to investigate the genotypic differences in stomatal frequency (F), leaf area (LA), leaf area duration (LAD), total stomatal number per plant (LA × F), and the relationship of these parameters to biomass production, grain yield and photosynthetic rate in 100 medium-duration genotypes. The differences in stomatal number per plant amongst genotypes was, as expected, influenced more by the leaf area than by the stomatal frequency of leaves at any canopy position. There were several genotypes with a consistently low leaf area but having a productivity under rainfed conditions that was equivalent to that of the high leaf area types. Mean biological yield and grain productivity were not significantly different between the two groups, although the differences in both LAD and stomatal number per plant were significant. Genotypes with a consistently low leaf area per plant associated with high biomass and grain yield were selected on the broad assumption that these genotypes may also show smaller canopy water loss under rainfed conditions, due to a low transpirational area. Photosynthetic 14 CO 2 fixation and gas exchange studies showed that the rate of leaf carbon fixation was two-fold higher in genotypes that had a consistently low leaf area but were able to produce dry matter and grain yield in the same amount as the high leaf area types. Such genotypes are desirable for rainfed or drought situations.