Abstract
Date palm (Phoenix dactylifera L.) is a major fruit tree in the Middle East and it is a plant considered to be tolerant to a variety of abiotic stresses, including salinity. However, the physiological basis of its salinity tolerance is not fully known. The objective of this study was to screen Omani date palm cultivars for tolerance or susceptibility to salt stress. Seedlings from 10 commercially important date palm cultivars were subjected to 240 mM NaCl, and several physiological parameters related to salinity tolerance traits were evaluated upon treatment. The cultivars were divided into two groups based on the dry weight (DW) of their leaf and root tissues, a parameter which was used as an indication of healthy growth. The results revealed that photosynthesis, electrolyte leakage (EL), and the shoot K+/Na+ ratio were all significantly reduced in the susceptible cultivars. In addition, the relative water content was higher in the tolerant cultivars in comparison with the susceptible ones. These results suggest that although date palm is tolerant to high salinity, there is variation in tolerance among different cultivars. Shoot Na+ exclusion, photosynthesis, and membrane stability are apparently the main determinants of tolerance and can be used in salinity tolerance screening of date palm. The results have shown new very tolerant cultivars (Manoma and Umsila) that could serve as genetic resources for improved date palm tolerance to salinity.
Highlights
Saline environments present a major worldwide threat to agriculture, resulting partly from the irrigation of arable lands with salt-containing water
The effect of salinity was investigated on the seedlings of 10 date palm cultivars in a glasshouse under controlled conditions
The first category comprises Zabad, HilaliOmani, Nashukharma, Khalas, Barni, and Abunarenja, while the second category is composed of Manoma, Umsila, Fard, and Nagal cultivars
Summary
Saline environments present a major worldwide threat to agriculture, resulting partly from the irrigation of arable lands with salt-containing water. Salinity is a multifactorial trait, the first effects of which are osmotic, whereby the presence of high concentrations of NaCl inhibits water uptake, leading to slow growth or growth arrest and eventual death for sensitive plants [2] This osmotic component is very severe because it induces stomatal closure via abscisic acid (ABA) signaling pathways, with a consequential reduction in gas exchange and the rate of photosynthesis [3]. Oxidative stress results from the production of reactive oxygen species (ROS) (mainly O2− ) in the electron transport chains of photosynthesis (chloroplast), respiration (mitochondria), and photorespiration (peroxisomes) These ROS often degrade membrane lipids through peroxidation, leading to electrolyte leakage and, the obstruction of cellular
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