Impact of Foliar Spray of Salicylic Acid on Morpho-Physiological and Biochemical Responses of Pea (Pisum sativum L.) under Drought Stress.

ABSTRACTThe accumulation of total soluble and cell wall-bound phenolics and total soluble proteins in Zea mays plants exposed to drought stress and foliar spray of salicylic acid (SA) at 10−4 mol/L and 10−5 mol/L was investigated. Drought stress was imposed at the four-leaf stage for 10 days (30–35% field capacity). Dehydration of maize leaves was accompanied by the accumulation of both total soluble and cell wall-bound phenolics, reduction in leaf relative water content (LRWC), and shoot and root growth attributes. Foliar spraying of SA further augmented the content of total soluble and cell wall-bound phenolics and total soluble proteins content under drought stress. SA ameliorated the adverse effects of drought stress on LRWC, shoot fresh weight, shoot dry weight, root fresh weight, root dry weight, root length and root area. The accumulation of both soluble and cell wall-bound phenolics by foliar spray of SA may be a mechanism related to SA-induced drought stress tolerance in maize. It was concluded that foliar spraying of SA at 10−5 mol/L can be highly economical and effective for modifying the effects of drought stress on maize at the four-leaf stage.

Drought stress is becoming a major threat to plant productivity loss in agricultural system. The present study was carried out to evaluate the physiological and biochemical alterations induced by salicylic acid (SA) in mustard plant under moderate drought stress conditions. Therefore, a pot culture experiment was conducted to test whether SA application at concentration of 0.5mM through foliar spray could protect the mustard (Brassica juncea L.) cultivar Pusa Jai Kisan subjected to drought stress on the basis of growth and photosynthesis. The treatments were as follows: (i) 100% FC+0mM SA, (ii) 50% FC+0mM SA, (iii) 100% FC+0.5mM SA and (iv) 50% FC+0.5mM SA. The control treatment received 100% field capacity (FC) irrigation, whereas moderate drought stress corresponded to 50% field capacity. Plants subjected to drought stress caused significant reduction in growth and photosynthetic parameters, activity of ribulose 1,5-bisphosphate carboxylase (Rubisco), nitrate reductase (NR), ATP-sulfurylase (ATPS) which accounted for decreased nitrogen (N) and sulfur (S) assimilation. Whereas, a pronounced increase was observed in proline metabolism. Exogenously applied 0.5mM SA alleviated the stress by increasing the proline production through the increase in γ-glutamyl kinase (GK) and decrease in proline oxidase (PROX) activity. In addition SA application restricted the ethylene formation by inhibiting the 1-aminocyclopropane carboxylic acid synthase (ACS) activity more conspicuously under moderate drought stress than no stress. These findings reflect that SA application alleviates the drought-induced decrease in growth and photosynthesis through increased proline content. Higher proline content was a result of increased N and S assimilation and increased synthesis of proline synthesizing enzyme which lowers the oxidative stress in mustard.

Milk thistle (Silybum marianum (L.) Gaertn) is a globally and widely used medicinal plant that contains silymarin. This plant has antioxidant, antimicrobial, anticancer, hepatoprotective, cardiovascular-protective, and neuroprotective effects. Plant quality, yield, and phytochemicals, especially silymarin content, change under various conditions like drought stress. Therefore, this research studied plant growth regulators (PGRs) like salicylic acid, spermidine, and brassinosteroid to increase plant tolerance to drought stress. Experimental treatments include different levels of irrigation (25%, 50%, 75%, and 90% field capacity), and foliar spraying including salicylic acid (75 and 150 mg/L), spermine (70 and 140 mg/L), and brassinosteroid (1 and 1.2 μM), separately, and water as a control and a secondary factor. The results revealed that the highest amount of leaf phenolic compounds was observed in the highest drought stress level (25%) and 75 mg/L salicylic acid application. Furthermore, brassinosteroid at different concentrations and salicylic acid (75 mg/L) increased leaf flavonoid content compared to other treatments. In 50% field capacity, foliar application of salicylic acid (150 mg/L) significantly increased seed yield by approximately 75% compared to control under the same stress level. Brassinosteroid application (1 μM) under 75% field capacity significantly increased the seed's taxifolin amount by 159%. Additionally, salicylic acid noticeably increased the silychristin concentration. The concentration of silydianin in the seed has also been increased under drought stress and foliar spraying with PGRs. Compared to the control, using spermidine below 75% field capacity caused an increase in its concentrations by over seven times. The highest silybin A amount was obtained in 50% field capacity and foliar150 mg/L salicylic acid. Taxifolin, silychristin, silydianin, silybinin B, iso-silybinin A, and iso-silybinin B compounds were identified in the seed extract. Generally, foliar spraying using plant growth regulators increased the number of silymarin compounds under drought stress conditions and field cultivation conditions.

The appraisal of foliar treatment of iron (Fe) and salicylic acid (SA) on plant under artificial magnetism is very crucial in understanding its impact on growth and development of plants. The present study was designed to document the potential role of Fe and SA on pea (Pisum sativum L.) Matore variety exposed to different magnetism treatments (geomagnetism and artificial magnetism). Thus a pot experiment was conducted using Completely Randomized Design under factorial with three replicates. Various artificial magnetic treatment were applied in pots prior to sowing. Further, 15 days germinated pea seedlings were foliarly supplemented with 250 ppm Fe and 250μM SA, moreover after 20 days of foliar fertilization plants were harvested to analyze and record various morpho-physiological attributes. Data elucidate significant variations in pea plants among different treatments. Artificial magnetism treatments in combination with foliar application of Fe and SA significantly improved various growth attributes (root and shoot length, fresh and dry weights of root and shoot, leaf area), photosynthetic pigments (Chl a, b and carotenoids) and the contents of soluble sugars. However, oxidative stress (H2O2 and MDA) enhanced under different magnetism treatment but foliar application of Fe and SA hampered the production of reactive oxygen species thereby limiting the concentration of H2O2 and MDA in plant tissues. Furthermore the accumulation of nutrients (iron, potassium and nitrate) profoundly increased under artificial magnetism treatment specifically under Fe and SA foliar treatment excluding nitrate where Fe foliar treatment tend to limit nitrate in plant. Consequently, the present research interestingly highlights progressive role of Fe and SA foliar treatment on pea plants under artificial magnetism. Thus, foliar supplementation may be suggested for better growth and development of plants combined with magnetic treatments.

Horticultural crops especially vegetables are most vulnerable to drought due to their higher irrigation needs. Hence, this study was undertaken to evaluate the adverse effects of drought stress and the beneficial effects of salicylic acid (SA) on physiological and biochemical attributes of okra plants under drought stress. For this purpose, a pot experiment was laid out in Complete Randomized Design (CRD) design. Okra seeds were primed with four different SA treatments i.e., 0 (control), 1, 2 and 3 mM and sown in pots (Ø 20 cm). After 14 days of germination, the plants were subjected to two drought levels i.e., 25% and 50% field capacity (FC) and after 20 days of germination regular foliar sprays of SA at 7 days interval were performed with aforementioned SA levels. Physiological parameters like fresh weight, dry weight, and length of plants along with biochemical attributes like chlorophyll (‘a’, ‘b’ and total), total carotenoids, total protein and proline contents, and electrolyte leakage were recorded. Results revealed that drought stress (25% FC) significantly reduced all the studied parameters and resulted in the lowest values of fresh weight (5.04 g), dry weight (1.33 g), length of plants (11.68 cm), chlorophyll ‘a’ content (5.97 mg/g FW), chlorophyll ‘b’ content (8.86 mg/g FW), total chlorophyll (14.84 mg/g FW), total carotenoids (4.96 mg/g FW) and total protein (1.05 mg/g FW), except proline content (6.81 mg/g FW) and electrolyte leakage (77.31%) which was increased. Application of SA under drought stress reduced the harmful effects of drought and application of 2 mM SA produced the maximum fresh weight (8.60 g), dry weight (2.51 g), length of plants (16.23 cm), chlorophyll ‘b’ content (14.47 mg/g FW), total protein (3.73 mg/g FW) and proline content (5.11 mg/g FW); whereas application of 3 mM SA showed the highest values of chlorophyll ‘a’ (8.91 mg/g FW), total chlorophyll content (23.20 mg/g FW) and carotenoids (7.93 mg/g FW), and the lowest value for electrolyte leakage (62.00%).

Drought is considered as one of the main environmental threats for plants that limits the growth and development. In the present study, salicylic acid (SA) was applied to mitigate the drought stress of rubber nursery plants. The study was conducted at Monaragala Sub Station, Rubber Research Institute of Sri Lanka during the dry months from May to September in 2015. The experimental design was Randomized Completed Block Design (RCBD) with five replicates. Treatments were drought-stressed (withholding of water), three concentrations of SA (0.1mM, 0.3mM and 0.5mM) and control(C) kept under regular irrigation. Drought was imposed by withholding water by weekly and lifesaving irrigation was done throughout the nursery period. Measurements were taken on morphological and physiological characters of seedling plants. Plants which were treated with SA as a soil drench at 0.1 mM, 0.3 and 0.5mM concentrations showed significant difference on drought stress plants when compare the stressed plant. Chlorophyll content and stomatal conductance (gs) in seedlings reduced drastically under moisture stressed conditions. Dry matter accumulation also decreased in drought stressed plants as compared to those treated with SA at 0.3 and 0.5mM concentrations. This indicates that the application of SA had a positive effect on stomatal conductance and biomass accumulation under water stressed conditions. In conclusion, the drought-stress decreased the growth of rubber nursery plants to a greater extent and exogenous application of SA at 0.3 mM and 0.5 mM concentrations found to be effective in alleviating drought stress under sub optimal conditions in the Intermediate zone in Sri Lanka.

Foliar application and seed priming of salicylic acid affect growth, fruit yield, and quality of grape tomato under drought stress

Trehalose (Tre) and salicylic acid (SA) are increasingly used to mitigate drought stress in crop plants. In this study, a pot experiment was performed to study the influence of Tre and SA applied individually or in combination on the growth, photosynthesis, and antioxidant responses of sweet basil (Ocimum basilicum L.) exposed to drought stress. Basil plants were watered to 60% or 100% field capacity with or without treatment with 30 mM Tre and/or 1 mM SA. Drought negatively affected growth, physiological parameters, and antioxidant responses. Application of Tre and/or SA resulted in growth recovery, increased photosynthesis, and reduced oxidative stress. Application of Tre mitigated the detrimental effects of drought more than SA. Furthermore, co-application of Tre and SA largely eliminated the negative impact of drought by reducing oxidative stress through increased activities of antioxidant enzymes superoxide dismutase, peroxidase, and catalase, as well as the accumulation of the protective osmolytes proline and glycine betaine. Combined Tre and SA application improved water use efficiency and reduced the amount of malondialdehyde in drought-stressed plants. Our results suggested that combined application of Tre and SA may trigger defense mechanisms of sweet basil to better mitigate oxidative stress induced by drought stress, thereby improving plant growth.

اسطوخودوس راست جزء گیاهان دارویی اسانس‌دار از خانواده نعناع و بومی ایران می باشد و به صورت سنتی و صادراتی در درمان درد مفاصل، دل‌پیچه و زکام کاربرد دارد. به منظور بررسی اثر پیش تیمار اسیدسالیسیلیک بر جوانه زنی بذر اسطوخودوس راست، در سطوح یکسان تنش شوری و خشکی دو آزمایش در قالب طرح کاملا تصادفی با سه سطح اسیدسالیسیلیک (0، 1/. و 5/. میلی مولار) و چهار سطح تنش شوری و خشکی (0، 2-، 4- و 6- بار) در سه تکرار انجام شد. از NaCl وPEG به ترتیب برای ایجاد تنش شوری و خشکی استفاده گردید. نتایج دو آزمایش نشان داد که با افزایش تنش شوری و خشکی به طور معنی دار از درصد جوانه زنی، طول ریشه چه، ساقه چه و بنیه بذر کاسته شد. در زمان عدم تنش شوری و خشکی، پیش تیمار با اسیدسالیسیلیک منجربه افزایش معنی داری در صفات مورد بررسی در مقایسه با شاهد نشد. ولی با اعمال تنش شوری و خشکی در سطح 4- و 6- بار، پیش تیمار باعث افزایش معنی دار تمامی صفات مورد بررسی شد. طول ساقه چه در بین سایر صفات از حساسیت بالاتری نسبت به تنش شوری و خشکی‌ برخوردار بود. علاوه‌‌بر آن مشاهده گردید که جوانه زنی بذرهای اسطوخودوس راست تا حدودی شرایط تنش خشکی را بهتر از شرایط شوری تحمل می‌کند. در مجموع نتایج نشان داد که پیش تیمار بذر توسط اسیدسالیسیلیک در مناطق شور و خشک می تواند باعث مقاومت بذر گیاه دارویی اسطوخودوس راست در مرحله جوانه زنی شود.

This study was carried out to investigate the effects of foliar spray of salicylic acid and ascorbic acid on some morpho-physiological traits of Pistacia vera cv. Badami-zarand under drought stress. The experiment was conducted during 2017-2018 in the greenhouse condition, in a factorial randomized complete block design with three replications on pot plants. The soil texture of experimental pots was sandy-loam. Moreover, the three factors were considered as follows: first factor, drought stress treatments at three levels; control (100% usable moisture content), moderate stress (60% usable moisture content), and severe stress (30% usable moisture content); second factor, salicylic acid, at three levels (0, 0.5mM, and 1mM); and ascorbic acid at three levels (0, 0.5mM, and 1mM). At the end of experiment related physiological, morphological, and biochemical traits related to 6-month-old seedlings were assessed including the fresh and dry weight of leaf, stem and root, number of leaves, leaf thickness, diameter and length of stem, length of root, relative water content, rate of electrolyte leakage, rate of proline accumulation, rate of glycine betaine accumulation, chlorophyll a content, chlorophyll b content, and total chlorophyll. Generally, the results indicated that the value of morphological traits showed a significant reduction in stress treatments. In this experiment, it was found that the application of salicylic acid and ascorbic acid can also reduce the adverse effects of moderate drought stress. Furthermore, it was identified that the response of plant to salicylic acid treatment is similar to ascorbic acid. In general, the application of salicylic acid with a concentration of 0.5mM and ascorbic acid with concentrations of 0.5mM and 1mM is recommended to improve the adaptation of pistachio seedlings under moderate stress.

Background: Determination of the most important level of salicylic acid to increase guar yield in drought stress conditions. Methods: In order to study the effect of potassium and salicylic acid on agricultural and physiological traits of guar in different irrigation treatments, a field experiment was conducted during 2020-2021 under the climatic conditions of Jiroft area (Kerman province, Iran) in the farm of research center and agricultural and natural resources education. The experimental treatments include three levels of irrigation (regular irrigation, stress 60 and 80% of the plant’s water requirement) in strip plots, three levels of salicylic acid (no application, 0.1 and 0.5 mM) as foliar spraying and two levels of potassium (no application and use of 100% of the plant’s need for potassium) in horizontal plots. Result: The results showed that drought stress and application of potassium and salicylic acid had a significant effect on all traits. Decreasing the amount of water led to a decrease in the physiological and functional characteristics of guar compared to regular irrigation. But potassium and salicylic acid were able to improve the yield characteristics and yield of guar under stress and non-stress conditions and the use of potassium + 0.5 mM salicylic acid were introduced as the best treatment for both conditions. This treatment at 60% stress led to an increase in plant height (91%), the number of leaves (37%), the number of pods (85%), seed number (70%), seed yield (100%), chlorophyll a (61%), chlorophyll b (59%) and carotenoid (100%) compared to the control treatment.

The role of exogenous individual or combined application of silicon (Si) and salicylic acid (SA) (control, 6mm Si, 1mm SA, and 6mm Si+1mm SA) on grain yield and some key physiological characteristics of wheat (Triticum aestivum L.) cvv. Shiraz (drought-sensitive) and Sirvan (drought-tolerant) was investigated under field water-stress conditions (100% and 40% field capacity). Drought stress caused a considerable reduction in biological yield, yield and yield components, relative water content and leaf water potential of both cultivars. Application of Si and SA effectively improved these parameters in water-deficit treatments. Moreover, water-limited conditions markedly promoted the activities of key antioxidant enzymes including peroxidase, ascorbate peroxidase, catalase and superoxide dismutase as well as the levels of malondialdehyde (MDA) and hydrogen peroxide (H2O2), while enhancing the accumulation of soluble sugars, potassium, magnesium and calcium in leaf tissues. Application of Si and SA further enhanced the activities of the key antioxidant enzymes and accumulation of osmolytes, and decreased the levels of H2O2 and MDA in drought-stressed plants; the positive effects of Si were greatest when it was applied with SA. Synergistic effects of Si+SA application on yield and physiological parameters were apparent compared with Si or SA applied separately. Water-stress alleviation and yield improvement in the wheat cultivars by Si and SA application was attributable to partly improved osmotic adjustment and antioxidant activity as well as to more favourable water status under stress conditions. Overall, Si and SA application proved to have great potential in promoting grain yield of wheat in drought-prone areas.

Moisture stress in rainfed areas has significant adverse impact on plant growth and yield. Exogenous application of plant bio-regulators (PBRs) plays an important role to mitigate drought stress in plants. A field experiment was conducted during rainy (kharif) seasons of 2018 and 2019 to explore the positive role of PBRs on the yield, economic feasibility and water use efficiency of maize grown under rainfed conditions. Ten treatments including PBRs, mulching and control were evaluated in a randomized block design. The result showed that foliar spray of salicylic acid (0.5 mM) with 1% urea solution improved the grain yield of maize by 24% as compared to control plot. Other PBRs such as glycine betaine, gibberellic acid and thiourea also increased the grain yield in the range of 10–21%. Application of 1% urea solution with PBRs synergise the effect of PBR to alleviate drought stress. The foliar applied PBRs maintained higher membrane stability index (73–78%), significantly increased relative water content (5–11%), chlorophyll content and decreased the proline content (11–21%) as compared to plants grown in control plot. Significant increase were noted in the rain and crop water use efficiency of maize with the foliar application of PBRs. Net returns were improved by 33% with application of salicylic acid (0.5 mM) + 1% urea as compared to control (₹49 × 103 /ha). Thus, foliar spray of salicylic acid (0.5 mM) with 1% urea solution could be an economic feasible strategy to reduce the adverse effects of drought and may increase the maize yield and water use efficiency.

Climate change is the biggest concern to the human kind and threat to agri-food security. Deficiency of water in soil and the ability of plants to uptake water is slowed down due rising temperature and microbial imbalance in soil. Salicylic acid plays an important role in mitigating drought stress and improves the overall production of crop. Humic acid is another amendment to cope against water stress and optimizes the yield. Apart from that, there is little known about their impact on soil geochemistry and that how soil health is altered. To investigate the effect of salicylic acid and humic acid on the drought experiment was conducted at University Research Farm (URF), PMAS Arid Agriculture University, Rawalpindi during summer 2023. The experiment was set up in randomized complete block design in two factorial arrangements with four replications. The first factor was comprised of mitigation strategies; salicylic acid, humic acid and chemical fertilizer, while second factor was water regimes; water stress and irrigation maintaining 60% field capacity. Plant attributes including chlorophyll content (SPAD value), total soluble protein content (mg/g), total free amino acid (mg/g), K+ content (mg/g), Na+ content (mg/g), 1000 grain weight (g) and grain yield (kg/ha) were measured and reported. On the other hand, soil parameters that were estimated are: soil pH, soil organic matter content (%), available N (ppm), available P (ppm), available K (ppm) and cation exchange capacity (cmol/kg). According to the data analysis, all of the features under study had a substantial impact from the mitigation approaches. The increased value of chlorophyll content (49.11 mg/g) was obtained in water stressed condition by the application of salicylic acid. Under water stressed regime and salicylic acid boosted the total soluble protein content (1.67 mg/g) and total free amino acid (31.93 mg/g) while grain yield (9451.7 kg/ha) was also boosted up by the amendment salicylic acid in maize. There was also increase in the values of soil pH (6.78), CEC (54.37 cmol/kg), SOM content (0.87%), available N (3.24 ppm), available P (26.14 ppm) and available K (211.23 ppm) drought conditions with the implementation of salicylic acid. Humic acid also positively impacted the drought stress and improved the maize yield (8436.2 kg/ha) under drought condition. Similarly, soil nutrient retention is also improved to large extent under water stress state; SOM content (0.49%), available N (2.36 ppm), available P (15.67 ppm) and available K (171.94 ppm). Overall, the study showed that amendment of salicylic acid and humic acid, is the greatest strategy to increase crop production and quality while also improving the health of the soil.

Seed treatments with salicylic and succinic acid to mitigate drought stress in flowering kale cv. 'Red Pigeon F1'