| Genotypic variation for water use efficiency and a correlated leaf-level trait, the dark-adapted leaf epidermal conductance (gdark ) has been previously identified among soybean cultivars adapted to Ontario, Canada. In the present work, parents of existing soybean mapping populations were screened for variation in these two traits to identify populations that would be suitable for identifying chromosomal regions controlling the traits. Second, a comparison of greenhouse and field data demonstrated that greenhouse screening experiments could predict cultivar differences for g dark in the field, but only when plants in the greenhouse were grown under a cyclic drought treatment. Third, greenhouse experiments were conducted to examine restrictions to photosynthesis in six soybean cultivars during recovery from drought stress. No treatment by cultivar interactions were found. Compared to control plants, drought-stressed plants showed residual limitations to photosynthesis 24 h after rewatering. The lower photosynthetic rates were primarily caused by reduced mesophyll conductance. |
