Solute Accumulation in Plant Cells

Abstract

This paper presents the concepts, the analytical methods, and the experimental devices used in a reappraisal of the problems of solute and water uptake which utilizes both quiescent and actively growing cells. The tissue used is drawn from the secondary phloem of the carrot root and, in all experiments, it is under conditions of aseptic culture which permit both inorganic and organic solutes to be studied for relatively long periods. The range of responses of the explanted carrot tissue has been observed in different media. These include simple inorganic salt solutions (CaCl2, KC1, NaCl, etc.), a full organic and inorganic nutrient medium and also the latter supplemented by stimuli that unleash the full ability of the otherwise resting cells to grow. The effects on both growth and composition of the cells have been observed with time. The high osmotic value of the mature non-growing cells may be made up, non-specifically, by salts (KC1, NaCl) or organic solutes (sugars) which are accumulated; when growth is not primarily involved these solutes may then behave reciprocally in accordance with supply, in the media, and demand, in the cells. Rapidly dividing cells, on the other hand, creating vacuoles, have lower osmotic value, greater specificity for potassium, and the solutes they store are under more endogenous than exogenous control. Between these extremes the solutes which are accumulated depend upon the levels of growth induced which in turn are responses to the nutrients and stimuli furnished. These observations and their interpretation set a trend for the papers that are to follow.