Salicylic acid and methyl jasmonate enhance drought tolerance in chamomile plants

Introduction: The dried flowers of chamomile contain many terpenoids and flavonoids contributing to its medicinal properties. Salicylic acid (SA) and methyl jasmonate (MeJA) have antioxidant properties and function as direct radical scavengers. Two Matricaria chamomilla cultivars (Bodgold and Hungary breed seeds) were used in this study to investigate the effects of exogenous application of SA and MeJA on protection against drought stress as well as on changes of malone dialdehyde (MDA) and electrolyte leakage index (ELI), and the fluctuation of proline and soluble sugars content in the leaves under drought stress. Methods: The experiment was conducted in a factorial design based on randomized complete blocks with three replicates. Chamomile plants were treated by two levels of drought stress as well as two different levels of MeJA (i.e., 0.0 and 100 &mu;M) and SA (i.e., 0.0 and 0.5 mM) solutions. Results: There was a dramatic drought induced increase in the MDA content (128) and ELI (49) in the leaves. Deleterious effect of drought stress was more severe in untreated plants than in treated ones. Treatments with SA and MeJA significantly improved drought tolerance in chamomile plants. These treatments effectively maintained membrane integrity, thereby retarding electrolyte leakage and membrane lipid peroxidation (MDA). Treatments with SA and MeJA were also effective in enhancing the antioxidant concentrations of proline and soluble sugars. Conclusion: The production of these antioxidants could have been part of a defence system against drought damage, reducing MDA and ELI and maintaining membrane stability.</p

The effect of drought stress and super absorbent polymer (A200) on agronomical traits of sunflower (Helianthus annuus L.) under field condition

In many areas of Iran, the reproductive growth stage of sunflower is exposed to the drought stress. Therefore, the investigation of irrigation management in the farm was necessary for increasing irrigation efficiency and decreasing water loss. The objective of the present study was to investigate the effect of different amounts of super absorbent polymer (A200) and levels of drought stress on morphological characteristics, such as: head diameter, stem diameter, plant height, 100-seed weight, seed yield and physiological characteristics, such as: relative water content (RWC), chlorophyll concentration of sunflower (cv. Master) under farm conditions. The experiment was carried out as a split plot based on randomized complete block design with three replicates. Three irrigation levels (irrigation after 6, 10 and 14 days) and five amounts of super absorbent polymer (0, 75, 150, 225 and 300 kg/ha) were set as main and sub-factors, respectively. Polymer was added at the fourteen leaf stage of sunflower to soil in deepness of root development. At this same stage, drought stress was applied. Polynomial models of each traits based on the ANOVA were fitted. The results indicated that drought stress has decreased significantly all the measured traits. In this study, seed yield has shown a significant decrease. After 6 days, irrigation has resulted in higher yields than other irrigation intervals. The highest seed yield was related to 300 kg/ha polymer application and the lowest one was related to irrigation after 14 days with no application of polymer. Regarding the limitation of water resources, super absorbent polymer could be a useful strategy for the sustainability of yield under drought stress in sunflower

Response of proline, soluble sugars and antioxidant enzymes in wheat (Triticum aestivum L.) to different irrigation regimes in greenhouse condition

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% (I0), 75% (I1), 50% (I2) and 25% (I3) of field capacity and growth stages: 50% emergence to booting stage (GS1) and booting stage to physiological maturity (GS2). 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 (I3). It was concluded that proline and soluble sugar levels were increased in wheat leaves under deficit irrigation regimes

Effect of drought stress and polymer on osmotic adjustment and photosynthetic pigments of sunflower

Water stress affects plant growth and crop productivity in the vast semi-arid and arid regions of Iran. The present study was aimed at investigating the effect of drought stress and super absorbent polymer (SAP) on the osmotic adjustment and carotenoid content of sunflower (cv. Master) under field condition. The experiment was carried out as a split plot based on randomized complete block design with three replications. Three irrigation levels (irrigation after 6, 10 and 14 days) and five amount of super absorbent polymer (SAP) (0, 75, 150, 225, 300 kg/ha) were set as main and sub factors, respectively. Polymer was added in fourteen leaves stage of sunflower to soil in deepness of roots development (by mixing with soil) and at this same stage drought stress was applied.The results showed that effect of different rates of super absorbent polymer and water stress in all traits were significant (P<0.001) as well as their interactive effect of two mentioned factors were significant (P <0.001).Drought stress significantly increased carotenoid content. Drought stress caused an increase in the concentration of soluble sugar and proline content in the leaves of sunflower. These results indicated that lowest amount in proline and soluble sugars accumulation were achieved at 300 kg ha-1 polymer compared with the control (without polymer) in all rates of water even under drought stress conditions.Our results showed that SAP can absorb and retain extremely large amounts of water, so protects the plants against drought

Seed reserve utilization and seedling growth of treated seeds of mountain rye (Secale montanum) as affected by drought stress

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

Effect of Water Deficit Stress and Foliar Application of Salicylic Acid on Antioxidants Enzymes Activity in Leaves of Thymus Daenensis Subsp. Lancifolius

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

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

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