ABSTRACT.The environmental stress such as, drought are serious obstacles for field crops in further areas of the world, especially in arid and semiarid regions. In order to investigate drought stress on seed reserve utilization and seedling growth of treated seeds of mountain rye (Secale montanum), an experiment was carried out. Factorial experiment was carried out in completely randomized design with three replications. The first factor was the seed treatments (unpriming, hydropriming and osmopriming) and the second factor was drought stress. To create drought stress, polyetylenglycol 6000 (PEG 6000) in osmotic levels at 0 (as control), -0.4, -0.8, -1.2 and -1.6 MPa were used. The results indicated that for these traits: germination percentage (GP), timson index (TI), energy of germination (EG), weight of utilized (mobilized) seed (WMSR), seed reserve utilization efficiency (SRUE), seedling dry weight (SLDW), and seed reserve depletion percentage (SRDP), was a significant treatment × drought interaction. Thus hydropriming and osmopriming improvement study traits in Secale montanum under drought stress. While in higher osmotic pressure the highest seed reserve utilization were obtained from osmopriming.
To evaluate the response of proline and soluble sugars content, catalase (CAT) and ascorbate peroxidase (APX) activity in wheat leaves to different irrigation regimes at two growth stages, a greenhouse factorial experiment was conducted in a completely randomized design (CRD) with three replications. The factors consisted of four different irrigation regimes as 100% (I 0), 75% (I 1), 50% (I 2) and 25% (I 3) of field capacity and growth stages: 50% emergence to booting stage (GS 1) and booting stage to physiological maturity (GS 2). Fresh leaf tissues were used to determine proline and soluble sugars content, CAT and APX activity. According to the results, irrigation regimes had significant effect on proline content, soluble sugars and APX activity, but no significant differences were detected among irrigation regimes for catalase (CAT) activity. Limited irrigation increased proline concentration and total soluble sugars in leaves. None of studied traits were affected by growth stages. Interaction between irrigation regimes and growth stages was not significant for all studied traits. Results indicated that the highest proline content (12 μmol/g DW), total soluble sugars (49 mg/g DW) and APX activity (42 μmol min-1 g-1 FW) were related to irrigation at 25% of field capacity (I 3). It was concluded that proline and soluble sugar levels were increased in wheat leaves under deficit irrigation regimes.
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.
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