Dynamics of growth and phytomass allocation in seedlings of Pistacia atlantica desf. versus Pistacia vera L. under salt stress

Salinity represents a major environmental constraint which can severely limit plant establishment in the arid and semi-arid areas in Tunisia. The present work was carried out to study the response of Pistacia vera L. and Pistacia atlantica Desf. seedlings to salt stress. Evaluation of salinity effects on both species was investigated using five increasing NaCl concentrations (0, 20, 40, 60 and 80 mM) during 60 days. The exposure to NaCl at seedlings stages, affects the majority of the studied parameters. Morphological parameters, such as height of shoot, number of green leaves, leaf area and consequently, phytomass allocation were significantly decreased. Additionally, P. vera accelerated leaf senescence. Both species showed a preferential allocation of the resources in favor of the roots for concentrations of NaCl lower than 40 mM. Whereas, only P. atlantica maintained a root growth for higher concentrations. Under salt stress, the specific leaf area decreased in P. atlantica (p<0.001) and translate a mechanism of tolerance to salinity. It appeared that both species tolerate concentrations lower than 40 mM of NaCl. However, for higher concentrations, P. atlantica seedlings are more tolerant.