COMPARISON OF RATES OF WATER INTAKE IN CONTIGUOUS REGIONS OF INTACT AND ISOLATED ROOTS

Abstract

By means of a technique employing micropotometers, simultaneous measurements of the rates of water absorption by contiguous regions were made in a saturated atmosphere on single intact and excised onion roots (Allium cepa) 65 mm. or less in length and less than a week old. The expts. on intact and excised roots of corresponding age, length, and history carried out under comparable conditions of humidity, temp., and light showed similar characteristics of behavior in water absorption with respect to (a) localization of the highest rates in relatively more basal regions, (b) an over-all increase of rates at each level with time throughout 12 two-hr. intervals (24-hr, period), and (c) fluctuations of rates in contiguous regions and in the gradient of distribution under constant external conditions. The rates of water intake at contiguous levels of the same root after excision were equal to, greater, or less than before excision. Both intact and excised roots which had been killed showed pronounced irregularities of water intake in contiguous regions; both liquid loss and uptake occurred at different levels during the same interval. The living root in position can deliver more water than that same root when dead.