Effect of water deficit stress and foliar application of salicylic acid on antioxidants enzymes activity in leaves of Thymus daenensis subsp. Lancifolius

Abstract

In order to study the effects of water deficit stress and foliar application of salicylic acid (SA) on the activity of five antioxidant enzymes (catalase - CAT; EC 1.11.1.6, ascorbate peroxidase - APX; EC 1.11.1.11, glutathione reductase - GR; EC 1.6.4.2, peroxidase - POD; EC 1.11.1.7 and polyphenol oxidase - PPO; 1.14.18.1) of Thymus daenensis (subsp. lancifolius), an experiment was conducted in factorial based on completely randomized design with three replicates, during 2013. Drought treated seedlings showed elevated levels of reactive oxygen species (ROSs), with a concomitant increase in the activities of the enzymes CAT, APX, GR, POD and PPO, compared to controls. Under medium water deficit, APX and PPO activities significantly increased by higher SA concentration (2 mM), but under control and sever water deficit conditions, there was no significant difference between 1 mM and 2 mM concentrations regarding APX and PPO activity. Under all levels of available water, increase in SA concentration from 0.1 mM to1 mM induced significant increase in GR activity. The maximum amount of GR (under medium water deficit condition) achieved from 1mM of SA. While the maximum amounts of APX, PPO (under medium water deficit condition), CAT and POD (under sever water deficit condition) achieved from 2 mM of SA. In total, our results suggest that application of SA (as a trigger of signal cascade) could be advantageous against water deficit stress, and could protect thyme plants in mentioned conditions.