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ARS Home » Northeast Area » Beltsville, Maryland (BARC) » Beltsville Agricultural Research Center » Adaptive Cropping Systems Laboratory » Research » Publications at this Location » Publication #332415

Title: Variation among soybean cultivars in mesophyll conductance and leaf water use efficiency

item Bunce, James

Submitted to: Plants
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/7/2016
Publication Date: 12/11/2016
Citation: Bunce, J.A. 2016. Variation among soybean cultivars in mesophyll conductance and leaf water use efficiency. PLANTS. 5:44-53.

Interpretive Summary: Conservation of water in agriculture is becoming increasingly important. This research examined fifteen varieties of soybean for their efficiency of using water in photosynthesis, and tested whether a resistance to the movement of carbon dioxide within leaves was related to their efficiency of water use. The varieties differed widely in their efficiency of water use in photosynthesis, but this was unrelated to the resistance to the movement of carbon dioxide within leaves. This research will be of interest to scientists attempted to increase crop water use efficiency.

Technical Abstract: Improving water use efficiency (WUE) may prove a useful way to adapt crop species to drought. Since the recognition of the importance of mesophyll conductance to CO2 movement from inside stomatal pores to the sites of photosynthetic carboxylation, there has been interest in how much intraspecific variation in mesophyll conductance exists, and how such variation may impact leaf WUE within C3 species. In this study mesophyll conductnace and leaf WUE of fifteen cultivars of soybeans grown under controlled conditions were measured under standardized environmental conditions. Leaf WUE varied by a factor of 2.6 among the cultivars, and mesophyll conductance varied by a factor of 8.6. However, there was no significant correlation between mesophyll conductance and leaf WUE. Leaf WUE was linearly related to the sub-stomatal CO2 concentration. The value of mesophyll conductance affected the ratio of maximum Rubisco carboxylation capacity calculated from the sub-stomatal CO2 concentration to that calculated from the CO2 concentration at the site of carboxylation. That is, variation in mesophyll conductance affected the efficiency of Rubisco carboxylation, but not leaf WUE. Nevertheless, there is considerable scope for genetically improving soybean leaf water use efficiency.