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

摘要

Plants of Argyranthemum coronopifolium were submitted to either 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). Effects of water and salt stresses on gas exchange, water relations and growth parameters were investigated in order to determine the mechanisms of resistance of A. coronopifolium to these kinds of stresses. Water and salt stress promoted reductions in leaf biomass due to both senescence and death of leaves; this has been considered an avoidance mechanism that minimizes water losses. The degree of osmotic adjustment reached by the plants was similar in both stresses studied; however, there was a greater effect of salt stress on both the growth and total chlorophyll content of plants. In addition, level of net photosynthesis did not recover in salt-treated plants after removal of the stress conditions. Thus, the osmotic adjustment reached via salinity treatment probably induced some damage to the photosynthetic apparatus that was not induced by the water stress.