Effect of water and salt stresses on the growth, gas exchange and water relations in Argyranthemum coronopifolium plants

Plants of Argyranthemum coronopifolium were submitted to water stress (preconditioned by watering every 3 days, two dry-wet cycles were imposed) and salt stress (15 days of exposure to 140 mm NaCl followed by a recovery period of 11 days), independently. Effects of water and salt stresses on gas exchange, water relations and growth parameters were investigated in order to know the resistance of A. coronopifolium to these kinds of stress. Water and salt stress promoted reductions in leaf biomass due to both senescence and death of leaves, what has been considered an avoidance mechanism that allows minimising water losses. The degree of osmotic adjustment reached by the plants was very similar in both stresses studied, however; the maintenance of turgor did not maintain growth. Probably, the osmotic adjustment reached via salinity treatment induced some damage to the photosynthetic apparatus that was not induced by the water stress. In this sense, reductions in the photosynthetic rate and chlorophyll content were observed even when the salts were removed. It suggested that there was a toxic effect of salt concentration that could also explain the greater effect on the growth of the salinized plants. (C) 1998 Elsevier Science Ireland Ltd. All rights reserved.