Abstract
Increasing world temperatures are bringing about climate changes creating abiotic stress in plants. Date palm offshoot leaves (Khadrawi cv.) were analyzed for chlorophyll Chl a, Chl b, Total Chl, Chl a/b ratio, anthocyanin and carotenoid subject to salinity, drought and temperature stress under field conditions. Results demonstrated that drought and salinity stress accompanied by high temperatures in July and August significantly reduced the Chl a, Chl b, and Total Chl relative to the control. Anthocyanins, carotenoids, hydrogen peroxide, and malondialdehyde were markedly higher in July and August (45 ºC), whereas September showed lower values in these substances. Temperature reduction to 35 °C accompanied by drought or salinity stress, brought about a critical increment in relative water content and a decrease in electrolyte leakage. Although the impact of drought and salinity stress continued, the reduced temperatures in September resulted in a reduction of abscisic acid and proline concentration. Cluster analysis showed the two groups. In this first group, the significant similarity between the treatments is illustrated by the influence of the high temperature of 43–45 ºC. Recovery of photosynthesis following low-temperature, for the most part, determines plant flexibility to water deficiencies and salinity. Thermal stress, associated with salinity or drought stress is more damaging to the photosynthetic pigments than any single factor.