Biological and Chemical Substances as Stimulants-Inducing Growth and Oil Yield in Lemongrass Under Salinity Stress

Abstract

This experiment was conducted at the Experimental Farm of Floriculture, Faculty of Agriculture, Assiut University, Assiut, Egypt during the two successive seasons of 2019 and 2020 to study the effect of some natural and synthetic growth stimulants on the growth measurements, percentage and oil yield and photosynthetic pigments of lemongrass (Cymbopogon citratus) plants under water salinity stress. Plants were treated with four growth stimulants (control, Moringa oleifera leaf extract (MLE) at 5% as spray, Bacillus subtilis + arbuscular mycorrhiza fungi as soil drench, benzylaminopurine (BAP) at 100 mg l -1 as pray). Irrigation water salinity treatments were control, 1000, 2000 and 4000 mg l -1 NaCl. The results showed that the higher salinity levels (2000 and 4000 mg l -1 NaCl) caused significant decreases in the morphological characteristics and oil yield, as well as the leaf content of photosynthetic pigments (chlorophyll a, b and carotenoids) of lemongrass plants compared to control and the lowest salinity level (1000 mg l -1 NaCl). The highest salinity level (4000 mg l -1 ) recorded the lowest values of these measurements. Among growth stimulants used, MLE gave the highest values of vegetative growth measurements, percentage and yield of oil/plant and chlorophyll content in fresh leaves, followed by B. subtilis + mycorrhiza fungi. Therefore, the study recommends spraying lemongrass plants with M. oleifera leaf extract at 5% or adding a mixture of B. subtilis with mycorrhizal fungi as natural growth stimulants to obtain the best morphological characteristics, percentage and yield of volatile oil under water salt stress conditions.