Root Application Efficacy of Plant Biostimulants in a Tunisian Portulaca Oleracea l. Cultivar Grown under Salt Stress

Plants biostimulants (PBs) have been shown to play multiple roles in plant growth and to improve crop tolerance to abiotic stresses such as salinity. The present investigation was undertaken for the first time to study the effect of PBs - a plant-derived protein hydrolysate (PH), a root activator (RA) and a root stimulator (RS) - on Portulaca oleracea L. tolerance to salt stress. For this purpose, a Tunisian P. oleracea cultivar was cultivated in pots under a greenhouse. Plants were treated with a factorial combination of three nutrient solutions (non-salt control, 50 and 100 mM NaCl) and three PBs were applied to roots. Growth and physiological parameters were then determined. Main results showed that salt stress decreased shoot and root dry biomass, chlorophyll and carotenoid contents while it increased the content in total soluble sugars, proline and relative water contents. However, root application of the three PBs induced some significant differences in the agronomical and physiological responses between PB treated and untreated plants when subjected to sodium chloride salinity from 50 and 100 mM NaCl. Overall, the present study proves that the root application of these PBs increases the performance of P. oleracea plants under salinity conditions. Therefore, PBs can be used to improve the salt-stress tolerance of vegetable crops by increasing their physiological responses to abiotic stress Portulaca oleracea L.; plant; salinity; biostimulant; growth; physiology