Abstract
Dublin
Royal Dublin Society, November 23.
H. H. DIXON and L. A. T. BALLARD: A simple method of showing tension inthe sap of a plant. If a branch of Vitis striata is clamped sufficientlytightly to close the vessels and to crush the cells around them, and is then cut off from the plant below the clamp and allowed to wilt completely, on afterwards cutting the stem above the clamp under water, the recovery of the shrivelled leaves and sagging petioles will be a matter of hours. Transpiration has caused the water-columns to break with the formation of bubbles in the vessels, and on cutting, atmospheric pressure partially refills the vessels so that the capillary forces around the remaining bubbles lead to their gradual complete solution. The water supply is re-established, and the observed tardy recovery brought about. If, however, the clamped stem is cut under water as soon as the petioles have sagged into a vertical position, but before the leaves show shrivelling, an immediate recovery will be noted, being complete within 10-12 minutesof the cutting. That complete recovery is not instantaneous seems to be due to delay in the release of the tension, owing to the resistance experienced by the water in entering the cut tracheae, and to semi-permanentdeformation of the tissues. The fact that the movements of the petioles at successive nodes are simultaneous is further justification for regarding these immediate movements as due to the release of tension in the water-columns.
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Societies and Academies. Nature 141, 132–133 (1938). https://doi.org/10.1038/141132a0
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DOI: https://doi.org/10.1038/141132a0