Silicon vs. selenium: A comparative study in mitigating osmotic and drought stress in durum wheat (Triticum durum Desf.)

Silicon (Si) and selenium (Se) are recognized as beneficial elements that may significantly improve plant's tolerance to drought stress. However, their action and efficiency on germination, biometric and physiological attributes are rarely compared on durum wheat under water-deficit conditions. This study highlights the effect of Si (15 mg L^-1) and Se (1 and 2 mg L^-1) seed priming on germination kinetic of four durum wheat varieties ('Karim', 'Maali', 'INRAT100', and 'Dhahbi') under osmotic stress (150 g L^-1 PEG6000). In addition, a pot experiment was undertaken in the year 2019/2020 to examine the fertigation benefits of these elements on growth and physiological durum wheat performance, using the same concentrations under two water regimes (70 and 30% field capacity). Except for phenols, flavonoids and carotenoids contents, our results indicated that osmotic/drought stress induced considerable reductions in germination rate, root, shoot and leaf physiological attributes. However, these drastic impacts were altered through seed priming and fertigation of Si and Se (2 mg L^-1). Se seed priming was more effective than that of Si, and inversely for the fertigation. These two nutrients Si and Se stimulated the elongation of roots (23.82%, 9.48%) better than that of shoots (20.55%, 10.44%), but improved the shoot fresh (27.79%, 10.37%) and dry weight (32%, 18.13%) better than that of roots. Specific interactions between studied traits were noted according to the water regime. In addition, genotype-specific effects of Si or Se were observed. The variety 'Karim', the lowest performing genotype, was the most receptive to stimulators. The positive changes resulting from Si and Se applications highlights the potential of these elements in boosting durum wheat plants to successfully acclimate to water-deficit conditions.