Interaction of osmotic adjustment and photosynthesis in winter wheat under soil drought

The relationship between photosynthesis and osmotic adjustment in winter wheat (Triticum aestivum L.) was studied in a controlled growth chamber under soil drought conditions. Leaf water potential, osmotic potential at full turgor, photosynthetic gas exchange, and chlorophyll fluorescence of plants under both control and stressed conditions were evaluated. Under a gradual drying process of soil water, the variability in the capacity of osmotic adjustment was observed, but not for a fast drying process of soil water. The plants that experienced the gradual drying process exhibited higher net photosynthetic gas exchange than those that experienced the fast drying process at a low water potential. Photosynthetic capacity of plants in the gradual drying process was greater than those in the fast drying process at low water potential. The data indicate that osmotic adjustment allows for maintenance of photosynthesis by stomatal adjustment and photosynthetic apparatus adjustment at low water potential.