The Regulation of Ion Homeostasis, Growth, and Biomass Allocation in Date Palm Ex Vitro Plants Depends on the Level of Water Salinity

The date palm, a central plant in the fragile oasis ecosystem, is considered one of the fruit species most tolerant to salt stress. However, the tolerance mechanisms involved are yet to be addressed and their evaluation until now was mainly based on heterogenous plant material such as seedlings or limited to in vitro experiment conditions. For these reasons, we propose to deepen our knowledge of the morphological and physiological responses to salt stress using acclimated ex vitro plants resulting from the propagation of a single genotype. The plants were irrigated with 0, 150, 300, or 450 mM NaCl solutions for four months. Our results showed that the influence of water salinity on growth and ion-homeostasis regulation was very dependent on stress levels. The 150 mM NaCl concentration was found to improve dry biomass by about 35%, but at higher salt concentrations (300 and 450 mM) it decreased by 40–65%. The shoot:root dry mass ratio decreased significantly at the 150 mM NaCl water concentration and then increased with increasing water salt concentration. The leaf:root ratio for Na+ and Cl− decreased significantly with increasing water salinity up to a concentration of 300 mM NaCl, and then stabilized with similar values for 300 mM and 450 mM NaCl. In contrast to Na+ and Cl−, leaf K+ content was significantly higher in the leaf than in the root for all salt treatments. Unlike Na+ and K+, Cl− was expelled to the surface of leaves in response to increased water salinity. Overall, date palm plants appear to be more capable of excluding Cl− than Na+ and of changing biomass allocation according to salt-stress level, and their leaves and roots both appear to play an important role in this tolerance strategy.All authors are funded through the Small Research group project from the Deanship of Scientific Research at King Khalid University under research grant number (R.G.P.1/295/43).Peer reviewe

Effect of the exposure period to different water salt levels on the morphological behavior of olive plants

International audienceThe increasing salinity of water and soil is one of the environmental factors that most threatens the sustainability of olive cultivation systems in the Mediterranean basin. The identification of plant material with high tolerance to this stress would be one of the ways to solve this challenge, but it is generally a slow and expensive process. The selection of the most reliably parameters involved in the response of the plant to salinity and that are easy to evaluate, could help to speed up the identification of the most tolerant genotypes. The objective of this study is to determine the most interesting morphological characters which could be used in future as early criteria in the selection process of olive tolerant genotypes. For that, young plants, three-month-old, were exposed to salinity (0, 4 and 8 g/L NaCl) during different periods of time (30, 50 and 70 days), and several morphological parameters were assessed. The obtained results showed that most of the parameters were affected by the concentration 8 g/L of NaCl after a treatment period of 50 days. The most affected parameters by this level of salinity were the plant height, the leaf number and the number of lateral shoots. The PCA analysis showed that the number of lateral shoots was poorly correlated with the other parameters, but the height and the leaf number were highly correlated with each other