Effect of putrescine application on some growth, biochemical and anatomical characteristics of Thymus vulgaris L. under drought stress

Abstract

This study investigated the effect of foliar application of putrescine on growth, biochemical, essential oil percent and morpho-anatomical characteristics of Thymus vulgaris L. under water deficit conditions. In pot experiments, plants were grown under two different irrigation levels 70–80% and 30–40% of water holding capacity and foliar sprayed with putrescine at 0, 0.1 and 0.2 mM twice at 10 and 50 days after transplanting. The results indicated that water stress caused significant reductions in the shoot, root fresh and dry weights whereas there was a significant increase in shoot/root dry matter ratio. Moreover, water stress led to multiple significant decreases in chlorophyll a, b concentration and chlorophyll a/b ratio. Whereas significant increases in the total soluble phenolic compounds and the activities of phenylalanine ammonia-lyase (PAL), polyphenol oxidase (PPO) enzymes and the essential oil percent were detected in plants exposed to drought stress. Stressed plants induced some morph-anatomical changes in roots, stems, and leaves to avoid tissue dehydration. Otherwise, putrescine reduce the impacts of drought by changing anatomical features, keeping chlorophyll concentrations, accumulation of total soluble phenolic compounds and activities some related enzymes. Consequently putrescine has the ability to improve growth and oil yield hence allowing thyme plants to grow better under water stress condition. Keywords: Thyme, Putrescine, Chlorophyll, Antioxidant enzymes, Phenolic compounds, Essential oil, Morphology, Anatomy, Adaptive mechanisms