Plants with limited transpiration rate (TR) under high vapor pressure deficit (VPD) offer the potential to conserve soil water and thus decrease the occurrence of soil water deficit. Genetic variability in TR response to VPD has been observed in the greenhouse for soybean (Glycine max (L.) Merr.) genotypes related to PI416937, but these differences have yet to be measured in the field. The objective of this study was to observe under field conditions leaf gas exchange properties of PI416937 in comparison to nine other genotypes to determine if it expressed limited TR at high VPD. Genotypic differences in stomatal conductance measurements (a proxy for TR) matched those obtained under controlled environment conditions. Genotypes varied from no stomatal response to VPD, to strong negative responses resulting in full stomata closure at ~4. kPa. There was a greater proportional genetic variability in stomatal conductance in the field (75% at high VPD) than was observed in the greenhouse, but this variation was correlated with greenhouse TR. However, photosynthesis was considerably limited in genotypes that had a stomatal response to VPD. Although field differences in photosynthetic capacity among genotypes were not correlated with greenhouse measurements, there was sufficient genetic variation to allow the possibility of selection of high photosynthetic capacity to overcome about a 34% decrease in stomatal conductance. Thus, a targeted breeding program to combine the water conserving TR-VPD response with increased photosynthetic capacity has the potential to increase soybean yields in field water-deficit environments.
Bibliographical noteFunding Information:
We thank Tommy Carter (USDA-ARS, Raleigh, NC) for establishing the field trial. This research was funded in part by USDA-CREES grant number 2006-35100-17263 and conducted while M.E.G. was a Giorgio Ruffolo Fellow in the Sustainability Science Program at Harvard University's Center for International Development. Support of CID and the Italian Ministry for Land, Environment and Sea is gratefully acknowledged.
Copyright 2011 Elsevier B.V., All rights reserved.
- Drought avoidance
- Stomatal conductance
- Water use efficiency