Effect of foliar application by growth bio- stimulants on the growth and productivity of lettuce plants under salinity stress

Two greenhouse experiments were conducted during 2019/2020 and 2020/2021 at the Agriculture Test Station, Faculty of Agriculture, Fayoum University, Egypt, to study effect of plant growth promoters on morphological characteristics, membrane permeability, leaf photosynthetic pigments content and productivity and quality of lettuce plants (Lactuca sativa L.) to elucidate their potential to reduce the harmful effect of soil salinity (ECe = 7.00 ± 0.20 dS m-¹). Treatments comprised with twelve of plant growth promoters; palm pollen grains (100 and 200 mg L-1), corn grain extract (100 and 200 mg L-1), soybean seed extract (100 and 200 mg L-1), mannitol (1500 and 3000 mg L-1), sorbitol (1500 and 3000mg L-1) and calcium phosphate (800 and 1000 Ca3(PO4)2 mg L-1), as well as, tap water. Three foliar applications of the thirteen treatments were made to run-off.; 25, 40 and 55 days after transplanting. The experimental layout was a randomized complete blocks design with five replications. All the foliar application of the twelve treatments (plant extracts, mannitol, sorbitol and calcium phosphate) were more effectively, with substantially higher mean values reported of morphological characteristics, membrane permeability and leaf photosynthetic pigments content comparing to control. Enhancement of the plant physio-biochemical components resulted from this., which reflected on improve productivity and quality of lettuce plants (cv. Big Bell) under the salinized soil stress of the Fayoum Governorate and other comparable areas. In general, foliar application of soybean seed extract at concentration of 200 mg L-1 or palm pollen grains extract at concentration of 100 mg L-1 were superior and particularly increased mean values were recorded for data recorded comparing to other treatments.