RESPONSE OF WOODY PLANT-CELLS TO DEHYDRATIVE STRESS

Low temperature scanning electron microscopy was used to evaluate changes in cell and tissue morphology in response to a dehydrative stress. Bark cortical cells of both Cornus florida L. (flowering dogwood) and Cornus sericea L. (red osier dogwood) were collapsed at low tissue moisture. Bark cortical cell volume was reduced, and cell walls appeared buckled and distorted. In contrast, the shape and volume of xylem ray parenchyma cells did not appear to change in response to the dehydrative stress treatment. There was no evidence of cell wall buckling, distortion, or separation in either of the two species. Instead the xylem my parenchyma cells within stressed tissue appeared the same as controls. These observations were similar to those reported regarding the response of woody tissues during freezing. The results do not support the hypothesis that rigid cell walls are a characteristic of plants that exhibit deep supercooling and that differences in cell wall rigidity distinguish species that supercool from species that do not.