The Effect of Anti-Transpiration and Plant Protective Materials on Vegetative and Physiological Traits of (Hyssopus officinalis L.) under Drought Stress

Hyssop (Hyssopus officinalis L.) is a perennial and belongs to the Lamiaceae family. Drought is the most critical environmental stress that adversely affects crop plant performance. The use of anti-transpiration and plant protective materials is one way that has recently been raised to improve plant resistance under stress conditions. The purpose of this experiment was to investigate the effect of anti-transpiration and plant protective materials on vegetative and physiological traits of Hyssop under drought stress and foliar application time.

This research was conducted as a split-plot factorial experiment based on a completely randomized design with three replications in 2016-2017. The experimental treatments included irrigation in three levels: 25% water available from the soil (control), 50% water available from the soil (mild stress), and 75% water available from the soil (severe stress) Were the main plots. Foliar application in four levels: water (control), kaolin (2.5%), chitosan (0.4 g/ l) and glycine amino acid (2.5 per thousand), and foliar application time: (vegetative and flowering, flowering) were the subplots. In the present study, dry leaf weight, flower dry weight, essential oil yield, shoot dry weight, economic yield, harvest index, proline, and soluble sugar were measured.

The results showed that at control stress level, the foliar application of water had the highest leaf dry weight (81.3 g/m2), shoot dry weight yield (140.5 g/m2), essential oil yield (9.40 g/m2), economic yield (81.3 g/ m²), and proline content (8.558 (µM/g FW). Moreover, during flowering and vegetative + flowering, kaolin's foliar application during vegetative+flowering had the highest dry flower weight (53 g/m2). At mild stress level, the foliar application of water during vegetative+flowering included the highest amount of soluble sugar (0.396 mg/g FW), and glycine foliar application at the flowering time had the highest harvest index (79%). Also, kaolin spraying during vegetative+flowering had the highest economic yield (73 g/m), and chitosan foliar application during vegetative+flowering had the highest shoot dry weight (111 g/m²) and essential oil yield (7.55 g/m2).

Due to the beneficial effects of antiperspirants and plant protection, they can be used as suitable solutions to increase plant production and reduce drought stress in arid and semi-arid regions.