The effect of water stress on morphological characteristic and essential oil content of improved sweet basil (Ocimum basilicum L.)

A pot experiment in Randomized Complete Blocks Design (RCBD) with six treatments in four replications was conducted to study the effect of water stress on morphological characteristics and essential oil content of improved basil (Ocimum basilicum c.v. Keshkeni luvelou). The irrigation treatments for induction of water stress were: A: (125 ml/ 12 h), B: (250 ml/ 24 h), C: (250 ml/ 48 h), D: (500 ml/ 72 h),
E: (250 ml/ 72 h), F: (125 ml/ 48 h). According to the results of statistical analysis, different levels of water stress had significant effect (P<0.01) on measured factors (herb fresh and dry weight, plant height, leaf number, root dry weight and essential oil content). The results showed that the highest fresh and dry herb produced in treatment B (250 ml/ 48 h) and the lowest one produced in treatment E (250 ml/72 h). There was not significant difference between treatment A and B as growth factor as concerned that is with increasing of irrigation time and decreasing of water content (250 ml to 125 ml), there was no significant effect on growth factors, in the other hand, with increasing of irrigation time and water content in treatment D, yield was higher than of the treatments except treatments A, B. These results showed that water stress influenced the yield and essential oil content of the plants and the best irrigation regime was determined as 500 ml/ 72 h. In conclusion, the highest essential oil content and yield produced in moderate water stress treatments (C and D).