جستجوی مقالات مرتبط با کلیدواژه « drought » در نشریات گروه « زیست شناسی »

This study was performed to compare some physiological and molecular responses of lemon balm to osmotic stress imposed by drought and salinity stresses with equal osmotic potential in hydroponic culture. Growing lemon balm plants in hydroponic culture were treated with drought and salinity stress using polyethylene glycol 6000 and sodium chloride for 14 days. Then, seedlings were sampled to evaluate the amount of photosynthetic pigments, proline, phenolic compounds, malondialdehyde, ion leakage percentage, phenylalanine ammonialyase activity and the amount of rosmarinic acid. Also, the expression of phenylalanine ammonialyase and rosmarinic acid synthase genes was examined by real-time PCR. This experiment was performed as a completely randomized design with three replications. The results showed that photosynthetic pigments, phenolic compounds, free proline, malondialdehyde, ion leakage, enzyme activity and relative expression of phenylalanine ammonialyase gene, relative expression of rosmarinic acid synthase and rosmarinic acid content affected by drought and salinity stresses at one percent level of probability. Also, a significant reduction in photosynthetic pigments was observed in drought and salinity stresses. The phenolic compounds content in plants under salinity stress increased compared to the plants under drought stress and untreated. The increase in free proline in plants under drought and salinity stresses was 11% and 25%, respectively. The amount of malondialdehyde and the percentage of ion leakage in plants under drought and salinity stress increased compared to the control plants. Relative gene expression and phenylalanine ammonialyase activity increased in salinity stress. Increasing the relative gene expression of rosmarinic acid synthase in drought and salinity stresses increased rosmarinic acid content by 42 and 60% compared to untreated plants. According to the results, lemon balm responded differently to drought and salinity with iso-osmotic potential. In another words, the plant had a better response to osmotic stress induced by salinity than drought with more increase in proline, phenolic compounds, rosmarinic acid contents, relative gene expression and phenylalanine ammonialyase enzyme activity.

Due to the dry climate and water shortage in Iran, the use of substances that can increase the plant's tolerance to water stress is very important. In this study, the effects of exogenous application of salicylic acid (SA) and kaolin (KL) on drought stress tolerance of tomato plants was evaluated in field conditions. Experimental factors included foliar application (including control, 0.5 mM SA, 2.5% KL and simultaneous application of SA + KL) and irrigation intervals (at four levels of 2, 4, 6 and 8 days). The results showed that increasing the irrigation interval in tomato plant led to a decrease in growth and yield in this plant. As compared to the controls, irrigation intervals of 4, 6 and 8 days decreased total yield as much as 9, 11 and 21%, respectively. The relative water content, total chlorophyll, transpiration and photosynthesis decreased while malondialdehyde, proline, peroxidase and hydrogen peroxide increased with the increase of irrigation intervals. Both SA and KL were effective in reducing the adverse effects of drought stress on plant growth and productivity.  Application of SA and KL improved plant growth and yield by increasing chlorophyll, relative water content, peroxidase activity, photosynthesis rate and transpiration. The highest effect of foliar spraying was observed at irrigation intervals of 6 and 8 days. The results also showed that the simultaneous application of SA + KL did not have a synergistic effect on plant growth and productivity in comparison to their separate application. According to the obtained results, the use of KL or SA is recommended to reduce the effects of prolonged irrigation on the tomato plant.

In order to study the effect of melatonin foliar application on photosynthetic pigments’ composition, phenolic compounds and soluble sugars on plants grown from different seed quality of safflower under water deficit condition, two field trials were conducted at Aburaihan Campus, University of Tehran in 2017 and 2018 growing seasons. The experimantal design was split-factorial randomized complete block design with four replicates. The treatments consisted of two levels of drought stress (1- normal irrigation (no-stress) and 2- irrigation after reaching 85% of soil moisture depletion of field capacity at flowering stage (drought stress)) were randomized to the main plots. Subplots were 4 treatments in number and consisted of a factorial combination of seed quality (1-stored seed and 2-recently harvested seeds) and foliar application (1-control (distilled water foliar application) and, 2- melatonin foliar application at 0.2 Mm concentration). The results showed that plant grown from recently harvested seed positively response to melatonin foliar application and this led to increase in chlrophyll a content by 33.33 % in comparison with control (distilled water foliar application). Also the results indicated that melatonin foliar application was successful to increase the flavonoids content only under non-stress condition over two seed quality treatments but on the contraty decreased flavonoids content under water deficit condition. The results demonstrated that melatonin foliar application decreased soluble sugars over both water deficit treatments. It’s seems that melatonin foliar application ameliorated the severity of stress because of its antioxidative charachteristic and provide an unstressed environment for plant so that there is no need to increase the level of metabolites that usually increased under drought condtition.

Drought is one of the major constraints to crop plant growth and development. The endophytic fungus, Piriformospora indica increases plant growth and development and enhances abiotic stress tolerance. To better understand the effect of P. indica inoculation on some morphophysiological traits and yield of Barley (Hordeum Vulgare L.) under drought stress condition, we designed a factorial experiment in a completely randomized design with three replications. The experimental factors included two fungal levels (inoculated and non-inoculated) and three drought levels (F.C., 50% F.C., 25% F.C.). The results showed that inoculation of barley plants with P. indica enhances dry weight of colonized plants under both well-watered (7%) and water-deficit conditions (43%). Based on experiment data, P. indica increased carbon (4%), potassium (20%), proline (2.03 times) and GABA (20%) content in inoculated plants compared with control plant under drought stress; Besides, endophyte fungus P. indica promoted the photosynthetic capacity of inoculated plants by increasing K/Na and C/N ratios, hence improve drought stress tolerance. The results also showed that P. indica increases the most of the measured yield parameters like as seed (86%) and spike number (66%), TGW (26%) and seed yield (1.9 times) in inoculated plants compared with control plants under ambient and stress condition. As, P. indica can be easily propagated in the absence of a host plant, it can be concluded that treatment with this endophytic fungus as bio-fertilizer can enhance the growth and yield of barley plants, which may act as an alternative to conventional chemical-based strategies.

To study the Evaluation of foliar application of spermidine, citric acid and proline (zero, 50 and 100 mg / l) on growth and flowering in pot marigold (Calendula officinalis L.) under drought stress (no stress (control), 25, 50 and 75% Crop capacity) was performed as a factorial experiment in a completely randomized design with three replications in a greenhouse located in northern Iran. The results of this study showed that increasing drought stress levels caused a significant decrease in fresh and dry weight of shoots and roots, plant height, root length, number of flowers, and longevity of the flower on the plant. Treatment of plants with different levels of spermidine, citric acid and proline significantly increased the evaluated traits, so that the highest fresh and dry weight of shoots and longevity of the flower on the plant was in proline 100 mg/l and control irrigation level and the highest fresh and dry weight of root and root length was in proline 100 mg/l and 75% of field capacity. Also, the highest plant height was in spermidine 100 mg/l and control irrigation level and the highest number of flowers were obtained in proline 50 mg/l and control irrigation level. In general, the results of this experiment showed that foliar application of 50 and 100 mg/l spermidine, citric acid and proline can partially compensate for the adverse effects of dehydration, but to enhance the growth and physiological characteristics of pot marigold, foliar application with proline 100 mg/l with 75% of field capacity is recommended.

To investigate physiological responses of black cumin to calcium silicate under salinity and drought stress condition with iso-osmotic potentials, a factorial experiment carried out based on the completely randomized design with three replications in research greenhouse of Faculty of Agriculture, Yasouj University, Iran in 2018. The first factor consisted of seven levels (salinity and drought stresses with iso-osmotic potentials of -2.4, -4.9 and -7.4 bar and control treatment) applied in Hoaglandchr('39')s solution. Salinity was applied with sodium chloride (NaCl) and drought with polyethylene glycol 6000 (PEG 6000). The results showed that at calcium silicate levels, salinity and drought stresses increased catalase and peroxidase activity, proline soluble sugars and malondialdehyde and also decreased leaf relative water content and leaf chlorophyll content. Silicate application mitigated the stress effects so that increased catalase and peroxidase activity, chlorophyll, proline and soluble sugars and decreased malondialdehyde content. In iso-osmotic potentials of drought compared with salinity, relative water content decreased but proline content, soluble sugars content, malondialdehyde content and catalase activity increased, indicating that black cumin sensitivity to drought is more than salinity based on physiological traits.

The current research was conducted with the aim to investigate the effect of salicylic acid on the growth traits, photosynthetic pigments and the amount of essential oil in Mentha piperita under drought stress. The factorial experiment was carried out in the form of randomized complete block design and with three repetitions. Factors included irrigation round at four levels (90 (control), 75, 45, and 20% field capacity) and salicylic acid at two levels (zero (control) and 60 ppm). The investigated traits included the plant height, number of lateral branches, length of lateral branches, number of nodes, fresh and dry weight of the plant, fresh and dry weight of the stem, chlorophyll a, b, and total, carotenoids, and essential oil percentage and yield. Results from this experiment showed that the effect of drought stress on all studied traits was significant at the statistical level of 1%. The mutual effect of drought stress on salicylic acid hormone for the length of lateral branches, fresh and dry weight of the plant, chlorophyll a, b, and total, and essential oil percentage and yield traits was significant. Stress caused a reduction in all traits except for fresh and dry weight of the stem; and the use of salicylic acid led to the reduced effects of stress such that the highest values of these traits were obtained from 60 ppm salicylic acid. Given the mutual effects, the highest values of essential oil percentage and yield obtained from 90% of field capacity and application of salicylic acid. Overall, the application of this hormone led to the improvement of qualitative and quantitative characteristics of Mentha piperita under drought stress.

Proline is an amino acid with a crucial role in ameliorating environmental stresses, including drought. In order to study the effect of external proline on the response of fennel to drought stress, three fennel genotypes (namely Urmia, Shiraz, and Kerman) were exposed to two levels of irrigation, i.e. control (34-45% of maximum allowable depletion in soil water) and drought (75-85% of maximum allowable depletion in soil water) and two levels of foliar-applied proline (0 and 20 mM) in a 4-replicate factorial randomized complete block pot experiment. Drought led to significant decreases in chlorophyll (Chl) and carotenoids (Cars) concentrations, leaf relative water content (RWC), ascorbate peroxidase (APX) and peroxidase (POX) activities, leaf water potential (ѱw), plant dry mass (DM) and seed weight and significant increases in leaf proline and polyphenols concentrations, and catalase (CAT) activity. Foliar-applied proline resulted in significant increases in membrane stability index (MSI), RWC, ѱw, proline and polyphenols concentrations, APX activity, plant DM and seed weight but it led to significant decreases in CAT and POX activities. Genotype Urmia out-numbered the remaining genotypes in terms of Chl and Cars concentrations, MSI, CAT and APX activities. There were significant correlations between leaf proline concentration and plant DM and seed weight under drought condition. Foliar-applied proline affected Chl and Cars differently in the drought-stressed and non-stressed plants. Furthermore, it affected plant seed weight in a genotype-dependent manner, as evidenced by 150% and 110% increases in Urmia and Shiraz and a 42.5% decrease in Kerman. It may be concluded that drought suppresses fennel growth, but foliar-applied proline is potent to mitigate the depression through increasing the leaf Chl, Cars, proline, and polyphenols concentrations, RWC and certain antioxidative enzymes activities in genotypes such as Urmia and Shiraz.

The present study was aimed to investigate the effect of drought stress on antioxidant defensive responses of three genotypes of Lolium perenne. This investigation was performed as factorial and a randomized complete design with three replications under field conditions. The results indicated that drought stress significantly decreased the relative water content (RWC), fresh and dry weight, chlorophyll a, chlorophyll b and carotenoid contents, while the concentration of H2O2 and proline increased. Also, compared to the control, the activities of catalase (CAT), ascorbate peroxidase (APX), guaiacol peroxidase (GPX) and superoxide dismutase (SOD) increased due to drought stress. Regarding results of the relative water content, the activity of antioxidant enzymes and proline content, it is concluded that genotype 1 had more tolerance to drought compared to the two other genotypes.