Acclimation of photosynthesis in Zea mays to low water potentials involves alterations in protoplast volume reduction.

Effects of water-stress treatment of Zea mays L. plants on protoplast volume and photosynthesis in leaf slices exposed to solutions of different osmotic potential (Ψ s) were studied. Decreased photosynthetic capacity in the leaf slices at low tissue Ψ w was associated with dehydration-induced protoplast-volume reduction. Leaf slices from plants exposed to in-situ water deficits exhibited greater photosynthetic capacity and relative protoplast volume at low water potential (Ψ w) invitro than tissue from control plants.In-situ water stress induced osmotic adjustment of the leaf tissue as determined by pressure/volume analysis. It is concluded that plant acclimation to low leaf Ψ w may involve a reduced degree of cell shrinkage at a given Ψ w. This acclimation would allow for the maintenance of relatively higher photosynthetic capacity at low water protentials.