Measuring Short-term Shoot Elongation of Douglas-fir Seedlings in Relation to Increasing Water Potential
A technique is described for measuring shoot elongation in seedlings of Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) under various levels of water potential. The seedlings were grown from seed in plastic pots. A recording micrometer, with two displacement-sensing transducers, was attached to the shoot of one seedling in a pot. Changes in shoot length were measured and recorded continuously before and after soil in the pot was watered. This technique of using two devices that are differentially connected, instead of a single device, makes possible a significant reduction in errors of measurement. Two phases of shoot elongation were observed after watering. In phase I, the rate was rapid and probably caused by rehydration of plant tissue. In phase II, the rate was more constant and probably caused by cell elongation. Forest Sci. 22:378-382.
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