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.
