Open Collections

Abstract

Preliminary experiments were conducted using western hemlock plug seedlings (Tsuga heterophylla Raf. Sarg.) to test the pressure chamber technique. Pressure-volume relationships were measured for the shoots and the relative importance of the matrix potential was assessed. Pressure-volume relationships were also measured for the roots and differences between the roots and the shoots were identified. The effects of transplant and drought stress on these pressure-volume relationships were tested and it was found that transplanting has very little effect on the water relations of the seedlings. A two-seek drought stress of 10 atm. resulted in a lowering of the osmotic potential of the shoot both at full turgor and at incipient plasmolysis. The roots showed no significant change. Shoot and root resistances to water flow were shown not to change significantly with either treatment. The bulk elastic modulus of the shoots was found to vary with a change in V₀, but was not shown to vary with the drought stress.