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Influence of light and form of nitrogen on chlorine requirement of kiwifruit
Author(s) -
SMITH G. S.,
CLARK C. J.,
BUWALDA J. G.,
GRAVETT I. M.
Publication year - 1988
Publication title -
new phytologist
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.742
H-Index - 244
eISSN - 1469-8137
pISSN - 0028-646X
DOI - 10.1111/j.1469-8137.1988.tb00231.x
Subject(s) - nitrate , actinidia deliciosa , chlorine , chloride , chemistry , nitrogen , potassium , potassium nitrate , nutrient , ammonium , ammonium chloride , inorganic ions , irradiance , botany , ion , biology , physics , organic chemistry , quantum mechanics
summary The extent to which light, potassium, and form of nitrogen (ammonium and nitrate‐nitrogen) modified the requirement by kiwifruit ( Actinidia deliciosa var. deliciosa ) for chlorine was examined in solution culture. A greater concentration of chloride was required in the nutrient solution for maximum growth under low irradiance than under high irradiance. In the absence of chloride, growth was severely restricted and the response to potassium was significantly reduced, especially under low light. Greater concentrations of chloride accumulated in the leaves of plants grown under high irradiance than under low irradiance. Increasing the concentration of nitrate in the leaves either by growing the plants under low light or by increasing the quantity of nitrate in the nutrient solution, substantially reduced the accumulation of chloride. The decrease in the concentration ot chloride was accompanied by an increase in the concentration of nitrate. Thus the combined concentration of nitrate and chloride was relatively constant over a wide range of treatments suggesting that a negative feedback mechanism may be operating in this species. However, while nitrate was preferentially accumulated by kiwifruit plants it could not substitute fully for chloride. Once the concentration of chloride in the leaves was decreased below 70μmolg −1 d. wt by competing nitrate ions, growth was substantially reduced. It is concluded that the effect of light on the chloride status of kiwifruit plants can largely be explained in terms of the strong competitive effect from nitrate ions, with greater concentrations of nitrate accumulating in the leaves under low irradiance than under high irradiance. The negative effect of potassium on the chloride status of the plants is not considered to be a specific physiological effect but rather the consequence of chloride, along with other non‐limiting nutrients, accumulating in the tissues of the severely potassium deficient plants. The ecological implications of the results are discussed in relation to features of the habitat in China where kiwifruit vines have evolved. The results of the present study are entirely consistent with this species having evolved in an environment where the availability of chloride and ammonium is relatively high while that of nitrate is severely restricted. It is concluded that the high concentration of chloride required in the tissues of kiwifruit vines is an adaptation which minimizes the expenditure of energy on the generation of osmotic pressure in the tissues rather than specifically maintaining charge balance.