effect of natural antitranspirant compounds on physiological and biological properties of basil (ocimum basilicum) under water stress condition

in order to study the effect of natural antitranspirant compound and water stress on growth, development and essential oil content of ocimumbasilicum a factorial experiment based on completely randomized design with three replicates was conducted. 3 levels of water stress (500 as control, 375 and 250 ml/day) and 3 antitranspirant compound (chitosan, plantago mucilage and psyllium mucilage) in 3 levels of 0.5, 1 and 1.5% (m/v) and applied during the plant growth. photosynthesis, transpiration, stomatal conductance, stomatal chamber co2, leaf temperature, fresh and dry weight of herb, essential oil percentage and content were measured. the results showed that water stress and antitranspirant application had a significant effect on all measured traits (p≤0.05 and p≤0.01). the highest values of these traits were observed in control for water stress treatment and different levels of antitranspirant compounds. transpiration levels from leaf were significantly decreased by antitranspirant compounds application. chitosan (1 and 1.5%) decreased transpiration by 200% over control. photosynthesis was also increased up to 30% by chitosan treatment (0.5 and 1) in comparison to control.also, antitranspirant compounds increasing dry matter yield in water stress condition but reducing essential oil % and yield in comparison with control. in general, according to the result of this experiment, antitranspirant compounds with natural origin are safe, biodegradable, easy available, low cost and alternatives which can be used in substitution with common chemical types.