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 (prec onditioned by watering every 3 days, two dry-wet cycles were imposed) and s alt stress (15 days of exposure to 140 mm NaCl followed by a recovery perio d of 11 days), independently. Effects of water and salt stresses on gas exc hange, water relations and growth parameters were investigated in order to know the resistance of A. coronopifolium to these kinds of stress. Water an d salt stress promoted reductions in leaf biomass due to both senescence an d death of leaves, what has been considered an avoidance mechanism that all ows minimising water losses. The degree of osmotic adjustment reached by th e plants was very similar in both stresses studied, however; the maintenanc e of turgor did not maintain growth. Probably, the osmotic adjustment reach ed via salinity treatment induced some damage to the photosynthetic apparat us that was not induced by the water stress. In this sense, reductions in t he photosynthetic rate and chlorophyll content were observed even when the salts were removed. It suggested that there was a toxic effect of salt conc entration that could also explain the greater effect on the growth of the s alinized plants. (C) 1998 Elsevier Science Ireland Ltd. All rights reserved .