THE NATURE OF THE AUXIN‐INDUCED WATER UPTAKE BY POTATO TISSUE

Abstract

SINCE THE DEMONSTRATION by Reinders (1938, 1942) that indoleacetic acid promotes water uptake by discs of potato tissue, the view has gained ground that the growth-stimulating action of auxin is intimately related to its effect on cellular water relations. Indeed, this effect has been studied by various workers (Commoner and Mazia, 1942, 1944; Commoner et al., 1943; van Overbeek, 1944; Levitt, 1948; Brauner and Hasman, 1949; Hackett, 1952), with a view to elucidating the mechanism of auxin action. In addition to the studies on potato tissue, effects of auxin on water movement have been shown in the following:-the exudation from decapitated stems (Skoog et al., 1938) and from seedling roots (Lundegardh, 1949); the water content of whole bean plants (Brown, 1946); the water absorption by Avena coleoptiles (Kelly, 1947), pea stem sections (Christiansen and Thimann, 1950), and submerged leaves (Vardar, 1950); the water-retaining capacity of bean fruits (Mitchell and Marth, 1950), and water uptake by discs cut from the floral parts of orchids (Hsiang, 1951). Mainly through studies of the elongation of isolated plant parts it has been established that the action of auxin in promoting growth by cell enlargement is intimately related to the cellular metabolism (for literature see Thimann, 1952) ; however, some evidence has been presented (Levitt, 1948) that suggests this is not the case for potato tissue. A preliminary study of the water absorption process in this tissue (Hackett and Thimann, 1950) showed, however, that it is inhibited by a number of inhibitors of oxidative enzymes and is promoted by auxins. In the present paper the effect of auxin is subjected to more detailed study and analysis. This was made possible by the finding (see Hackett, 1952) that c-naphthaleneacetic acid induces a very large water uptake in potato tissue. The results should make it possible to clarify the relation between metabolism and water uptake, in the presence of auxin, and to compare the effects of auxin exerted on growth by cell elongation with those exerted on water uptake. For this analysis, we have studied the effects of various agents on water uptake; these included enzyme inhibitors and low oxygen pressures, which are known to block or retard cellular metabolic activities.