ADJUSTMENT PROCESSES IN ASH AND WATER-STR ESS SITUATION

This study, performed opt the leaves of ash tree (Fraxinus communis L. ) indicated that osmotic and elastic adjustment processes contributed greatly to drought adaptation mechanisms. Pressure plants submitted to experimental water stress, showed a decrease in the osmotic potential at full turgor and at zero turgor. This osmotic adjustment was also d emonstrated in stressed plant by the increase in the level of the main organic compound which occurred in ash leaves, malate and mannitol. B y calculating the elastic modulus of the foliar tissues it was also sh own that, at the same time, the cell wall of the stressed plants becam e less elastic This mechanism, elastic adjustment was similar to the s ame process exhibited by many xerophilic plants. The advantage and ben efits of the elastic adjustment are discussed in relation to the water availability of the plant.