نشریه فیزیولوژی محیطی گیاهی
پیاپی 67 (پاییز 1401)

Applying biological agents for increasing plant growth and their resistance to different tensions is of particular importance. In the present study, an attempt was made to isolate and identify plant growth-promoting bacteria from soil samples and to evaluate their ability to help the tomato plant cope with drought stress. Soil samples were collected from wheat and barley farms around Karaj and after isolation and initial purification of phosphate solubilizing, nitrogen fixing, and siderophore producing strains, they were isolated using PVK media culture, nifH gene PCR, and CAS-agar media culture, respectively. The identified isolates were then analyzed in terms of their drought tolerance in an environment containing polyethylene glycol. Finally, tomato seedlings were inoculated with bacterial isolates (belonging to the Bacillus, Brevibacterium, and Actinomycetes genera) before they were grown under drought stress at three osmotic pressure levels of 0, -0.4, and -0.8 MPa. Then, sodium and potassium ion contents of leaves, roots, and stems were measured using a flame photometer while calcium contents of the same organs were assayed through atomic absorption measurement. Results showed that all five isolates capable of dissolving phosphate, nitrogen fixation, and siderophore production were able to withstand drought up to -0.8 MPa osmotic pressure. All these isolates significantly affected drought stress and the intensity of ions reduction in leaves, roots, and stems compared with the control plants. The results of the present study showed that inoculation of the bacterial isolates considering their ability in siderophore production and nitrogen fixation may help the plant to resist drought stress.

Seed osmopriming is an effective strategy to improve the germination process. Screening and estimating the optimal concentrations of different osmotic compounds is the first step in seed osmopriming. In this study, the effects of treatment with single osmotic compounds were initially evaluated at different concentrations, namely NaCl (0, 1, 2, 3, 4, 5, 10, 20, 30 g/l), ZnSO4 (0, 1, 5, 10, 20, 30 and 40 mM), proline (0, 1, 5, 10, 20, 30 and 40 mM), and trehalose (0, 1, 5, 10, 20, 30 and 40 mM) on wheat seeds. Then, the surface-response method was designed in the form of a Box-Benken design. Results showed a significant increase in wheat seed germination at concentrations of 3 and 10 g/l NaCl, 1 and 20 mM ZnSO4, 1 and 10 mM proline, and 0 and 1 mM trehalose. These concentrations were validated using the surface-response method and experiments. The values of coefficient of determination (R2 = 0.99) and adjusted R2 (R2adj = 0.99) showed that the obtained model is suitable for data analysis. One-way analysis of variance confirmed the quadratic model as the best model to determine the interaction of the studied variables (P<0.0001). The optimal values  were proposed as a combination of 3 g/l NaCl, 1 mM ZnSO4, and 1 mM proline. In another experiment, using the values predicted by the model, it was found that the surface-response method can be used in screening and germination optimization tests. The results of the follow up experiment using the values determined in the model revealed that the surface-response method can be considered in screening and optimization studies of seed germination.

Salinity stress is one of the important factors in decreasing the rate of growth and changing physiologic and metabolic processes of plants. In the present study to investigate the effect of salinity stress on physiological and biochemical performances and also gene expressions of Artemisia absinthium plant, an experiment was conducted with three level of salinity (0, 75, and 15 Mmol NaCl) in a completely randomized design with three replications under greenhouse conditions. Results showed that salinity stress decreased the rate of growth parameters in the plants including shoot length, root length, wet shoot weight, wet root weight, dry shoot weight, and dry root weight. Also, salinity decreased the levels of potassium, calcium, magnesium, and iron ions while increasing sodium levels in the plants. Increased salinity stress increased levels of proline, malondialdehyde, phenolic compounds, and activities of some antioxidant enzymes while it led to protein reduction in the plants under study. The expression of CYP71AV1 and ADS genes reduced to minimum at 150 Mmol and 75 Mmol NaCl treatments, respectively leading to reduced level of artemisinin in the Artemisia absinthium plants. According to the findings of this study, it might be argued that in its attempt to confront salinity stress induced fromsodium chloride, Artemisia absinthium employs the system of increased level of antioxidant enzymes activity, osmotic potential regulators, and phenolic compounds. Also, decreased expression of ADS gene can be an effective factor in reducing artemisinin contents in Artemisia absinthium.

The current study agreenhouse research was designed to evaluate the reaction of fennel (Foeniculum vulgare Mill.) genotypes to salt stress (NaCl salinity) and Salicylic acid, to study of the proteome profile of leaves for identifying molecular pathway involved in salt stress tolerance. The study was designed as factorial experiment using a randomized complete block design in three replications. Treatments are included NaCl solutions at three levels (0, 100, 200 mM) as salinity stress, Salicylic acid at two levels (0, 0/5 mM) and five genotypes. Agronomic and physiochemical traits were included: fresh and dry weight of ariel plant and roots, plant height, root length, fresh and dry weight of total plant, chlorophyll a, b and carotenoids, total chlorophyll, Na+ and K+ content, K+/Na+ ratio, malondialdehyde (MDA), Hydrogen peroxide (H2O2) and Total soluble carbohydrate (TSC) of leaves. The analysis of variance revealed significant differences for main and interaction effects in examined traits. German and Moghan genotypes were expressed as the most tolerant and sensitive genotypes based on Arunachalam method, respectively.

The aim of this study was to investigate the effect of sesame aqueous extract on growth parameters, proline, chlorophyll pigments, and soluble sugars of leaves and roots of soybean and morning-glory (Ipomoea sp.). To this end, an experiment was conducted as a split plot in a randomized complete block design with three replications in the Research Farm of Golestan Agricultural and Natural Resources Research and Education Center. The main plot included 5 different concentrations of sesame extract (0, 2.5, 5, 10, and 10% with surfactant) and the sub-plot included the target plants at two levels (Soybean and Ipomoea sp). Results showed that the effects of different concentrations of sesame on growth parameters such as root length, fresh and dry weight of shoots and roots, and number of leaves of soybeans and Ipomoea sp were significant different while photosynthetic pigments of these two plants were not influenced by the allelopathic effects of sesame crop extract. Based on the obtained data, increasing the concentration of sesame extract led to increases in the amount of soluble sugars in soybean leaves and roots while decreasing this parameter in Ipomoea sp. Also, the amount of proline in the roots and shoots of soybean and Ipomoea plants increased under effect of sesame extract, in which the increase in the proline content of soybean leaves was significant in comparison with Ipomoea plants. Generally, based on the obtained results, the allelopathic effect of aqueous extract of sesame on morphophysiological parameters of Ipomoea sp. weed in this study was more than those in soybeans, and a complementary research on seed and crop yield, may make it possible to suggest application of sesame extract as a natural herbicide in soybean fields.

In order to study the effects of mycorrhizae and foliar application of nano Fe and Zn oxides on nodulation and quantitative and qualitative yield of lentil under rain fed conditions, a factorial experiment was conducted based on randomized complete block design with three replications in a farm at Zardalo village, Ardabil province during 2017-2018. Treatments included foliar application of nano Fe and Zn oxides at four levels (foliar application with water as control, foliar application of nano iron oxide (0.6 gL-1), nano zinc oxide (0.6 gL-1), combined foliar application of nano Fe and Zn oxides (0.3 g L-1 each), and application of mycorrhiza at four levels (no application of mycorrhiza as control, application of Mycorrhizae mosseae, Mycorrhiza intraradices, and combined application of Mycorrhiza intraradices with mycorrhiza mosseae). Means comparison showed that foliar application of nano Fe-Zn oxides as well as combined application of mycorrhizal mosseae and intraradices increased number of active nodules per plant, percentage of active nodules per plant, 100 grain weight, and grain yield by 173.2, 93.08, 36.58, and 58.34% respectively in comparison with no foliar application of nano Fe-Zn oxide and no application of mycorrhiza. Also, combined foliar application of nano Fe-Zn oxide along with mycorrhiza mosseae and intraradices increased respectively the number of grains per pod, number of pods per plant, dry weight of root, zinc content of grains, and protein contentof grains increased by 42.14, 95.17, 12o, 58.2, and 47.55%, respectively in comparison with no application of mycorrhiza and nano Fe-Zn oxide. It seems that foliar application of nano Fe-Zn oxide and mycorrhiza application owing to improving some morphophysiological traits can be considered as a proper method for increasing quantitative and qualitative yield and mitigating the effects of water deficit in rain fed conditions.

Various environmental factors including altitude and soil properties affect the growth and production of plants in natural ecosystems. Sweet violet (Viola odoratata L.) is a gramineous and perennial plant of the Violaceae family and grows as a wildflower in the mountainous areas of northern Iran and some other regions of the country. This study was performed to compare the phytochemical properties and antioxidant activity of Viola odoratata L. shoot and root extracts in nine habitats of Mazandaran province in March 2020. To investigate the analysis, leaf, flower and root organs of the plant in the flowering stage were collected from nine habitats of Mazandaran province along with soil samples of these areas in March 2018. After collecting the root and shoot samples at the florescence stage and preparing methanolic extract through ultrasonic method, the phenolic and flavonoid contents were determined by Folin-Ciocalteu and aluminum chloride colorimetric methods, respectively, the antioxidant activities were assayed by Diphenyl Picrylhydrazyl (DPPH), and the anthocyanin contents of flowers were measured by Wagner method. According to the findings, phenolic contents of the flowers and leaves decreased and increased, respectively with increasing height, and percentage antioxidant activities of the flowers increased while the amount of flavonoids was not affected by the habitat altitude. Analysis of soil properties revealed that the anthocyanin contents of flowers increased under the effect of deficient absorbable phosphorus in habitat 3 (Firoozjah Babol) and habitat 6 (Mohammadabad Behshahr). Also in the study of secondary metabolites, Sweet violets in habitat 7 had 67.95% and 86.18% antioxidant activities in flowers and roots, respectively; leaf and root phenol contents of 142.32 mg/g and 55.21 mg/g, respectively, and 6.52 μmol/g flower anthocyanin, so it can be selected as the superior region, and samples from this region can be used as gene banks in sexual and asexual reproduction.

In this study, the mechanism of cold stress tolerance in cucumber fruits pretreated with folic acid was investigated. Control group and the group treated with 5 mgL-1 folic acid were stored for 15 days at 4 °‌-C. The results showed that, in comparison with the control, treatment with folic acid resulted in reduced chilling injury and decreased electrolyte leakage. The cucumber fruits treated with folic acid showed higher chlorophyll contents in storage conditions with suppressed chlorophyllase enzyme activity. Exogenous folic acid treatment also increased the activity of arginine decarboxylase and ornithine decarboxylase resulting in the accumulation of polyamine contents. Also, higher levels of proline were observed in the fruits treated with folic acid, which is attributed to the increased activity of proline synthesizing enzymes △1-pyrroline-5-carboxylate syntheses and ornithine aminotransferase and also reduced activity of proline dehydrogenase enzyme that decompose proline. Generally, the results showed that folic acid treatment increased the resistance to the cold stress by regulating the activity of enzymes involved in the biosynthesis of proline, chlorophyll, and polyamines.

The transition from transplanting rice cultivation to direct-seeding rice cultivation has recently begun in Iran, especially in Golestan province. No information is yet available on the effect of humic acid and plant density on paddy yield and some of its biochemical traits. For this purpose, an experiment was conducted in a research farm located in Gonbad city during May to September 2019 in the form of split plot-factorial based on randomized complete block design with three replications. Plant density (plant spacing per row) was considered as the main factor with 4 levels (5, 10, 15, and 20 cm) and humic acid consumption at 2 levels (humic acid consumption, no humic acid consumption) was considered as subplots. Humic acid fertilizer with a concentration of 250 ml per hectare was added in three stages including tillering (4-6 leaves), stalking (20-30 days after tillering), and before panicle initiation. Results showed that the effects of plant spacing on row and humic acid application on 1000-seed weight, paddy yield, biological yield, harvest index, grain protein, water use efficiency, and chlorophyll a and b and total chlorophyll were significant. Considering 5 and 10 cm plant spacing on rows along with humic acid application had the highest rice yield and water use efficiency. Also, chlorophyll content showed a significant change with increasing plant density and application of humic acid with a significant increase in chlorophyll a and b, which in turn was effective in increasing paddy yield. Rice protein also showed the highest level in 10 cm spacing between plants on each row along with the application of humic acid.

Drought stress affects various aspects of plant growth (vegetative growth, reproductive growth, flower formation, pollination, fertilization, and seed formation). To reduce the effects of drought stress on plants, it is important to determine the mechanisms of plant response to drought stress. In response to drought stress, plants experience morphophysiological, biochemical, cellular, and molecular changes with the ultimate result of improved root system, leaf structure, osmotic regulation, relative water content, and stomatal regulation. The phenotypic manifestations in plants facing drought stress include drought escape (early or short growing period, day length sensitivity, and tiller control), drought avoidance (developed root system, stomatal conductance, size and frequency of stomata, accumulation of abscisic acid, and cuticle thickness and waxy crust on the leaf), drought tolerance (osmotic pressure regulation, passive regulation, active regulation, proline accumulation, and displacement of sap phloem materials), and recovery (improvement). Management methods to improve drought stress tolerance include the development of tolerant cultivars, the use of external osmotic protectors such as glycine betaine and proline, spraying with plant hormones such as abscisic acid, salicylic acid (aspirin), gibberellic acid, jasmonic acid, brasino steroids, and polyamines, application of foreign substances with antioxidants such as glutathione, ascorbic acid (vitamin C), tocopherol (vitamin E), and nitric oxide, foliar application of micronutrients such as iron and zinc, spraying with trace elements such as silicon and selenium, and microbial interactions of plants such as growth-promoting bacteria and fungi. This review article is a content analysis study that was carried out by searching related articles in reliable sites (Google scholar, Web of science, PubMed, Scopus, Sid) aiming to investigate the effects, mechanisms of tolerance, research methods, important measurable traits, drought stress management, and control.