Application Of Gamma-aminobutyric Acid Research Articles

Exogenous Application of Gamma Aminobutyric Acid Improves the Morpho-Physiological and Biochemical Attributes in Lavandula dentata L. under Salinity Stress

Exogenous Application of Gamma Aminobutyric Acid Improves the Morpho-Physiological and Biochemical Attributes in Lavandula dentata L. under Salinity Stress

Combined application of acetylcholine (ACh) and gamma-aminobutyric acid (GABA) mitigates the effects of water deficit in soybean

Bioregulatory substances, such as acetylcholine (ACh) and γ-aminobutyric acid (GABA), have shown promise in mitigating water deficit effects on plants. Their action on plant physiology, particularly in stomatal regulation and osmoprotection, contributes to enhanced agricultural productivity. Regarding soybean plants, changes in the metabolic profile that could justify the improvement in physiological performance and growth are still unknown. This study investigated the impact of combined ACh:GABA application during soybean V4 and R2 stages using physiological assessments and NMR-based metabolomics. Two equimolar doses (2 and 8 mM) of ACh:GABA were applied to soybean plants subjected to two water regimes: 100 % of field capacity (continuously irrigated) and water deficit (water suspension). Results demonstrated enhanced gas exchange, biomass, and chlorophyll content, alongside favorable enzymatic activity. NMR analysis revealed metabolites countering oxidative stress, supporting osmoprotection, and contributing to soybean development and energy supply. The 8 mM ACh:GABA application notably improved plant performance, showcasing potential for water deficit mitigation in soybeans.

Effects of exogenous GABA on physiological characteristics of licorice seedlings under saline-alkali stress

Licorice is widespread in arid and semi-arid areas, but high soil salinity has always been a limiting factor for vegetation growth in these areas. Gamma-aminobutyric acid (GABA) is a signaling molecule that can regulate tolerance in plant. However, the mechanism by which exogenous GABA regulates the response of licorice to saline-alkali stress is not yet clear. In this study, we investigated the effects of exogenous GABA on growth parameters, oxidative damage, hormone levels and photosynthetic indices of licorice seedlings under different combinations of saline and alkali stress conditions. The experiment involved eight treatments: CK, distilled water (control); CK + GABA, 0.1 mM GABA; salt stress (SS), 150 mM NaCl; SS + GABA, 150 mM NaCl + 0.1 mM GABA; alkali stress (AS), 10 mM Na2CO3; AS + GABA, 10 mM Na2CO3 + 0.1 mM GABA; mixed saline-alkali stress (MAS), 150 mM NaCl + 10 mM Na2CO3; MAS + GABA, 150 mM NaCl + 10 mM Na2CO3 + 0.1 mM GABA. Our results showed that the inhibitory effects of SS and MAS on the seedling height, root length and root-shoot ratio were significantly alleviated by exogenous GABA. Although soluble sugars, chlorophyll a, total chlorophyll, and superoxide dismutase (SOD) activity were lower in the leaves of the seedlings in the SS treatment compared with the control, these physiological parameters increased significantly after GABA application. Exogenous GABA improved glutathione (GSH) activity in both the leaves and roots of the seedlings during the AS treatment. Additionally, take advantage of GABA led to an increase in ABA, GA and IAA contents in leaves under SS, AS and MAS treatments. Furthermore, the photosynthetic parameters, including Pn, gs, Tr, ETR and qP, significantly increased following the utilization of GABA in both the SS and MAS treatments. Therefore, the application of exogenous GABA can reduce the accumulation of harmful substances, preserve cell morphology, and enhance cell function under saline, alkali, and saline-alkali stress. This enhances the resistance of licorice seedlings to stress conditions and reduces physiological damage.

Integrating transcriptome and metabolome to explore the growth-promoting mechanisms of GABA in blueberry plantlets.

Tissue culture technology is the main method for the commercial propagation of blueberry plants, but blueberry plantlets grow slowly and have long growth cycles under in vitro propagation, resulting in low propagation efficiency. In addition, the long culturing time can also result in reduced nutrient content in the culture medium, and the accumulation of toxic and harmful substances that can lead to weak growth for the plantlets or browning and vitrification, which ultimately can seriously reduce the quality of the plantlets. Gamma-aminobutyric acid (GABA) is a four-carbon non-protein amino acid that can improve plant resistance to various stresses and promote plant growth, but the effects of its application and mechanism in tissue culture are still unclear. In this study, the effects of GABA on the growth of in vitro blueberry plantlets were analyzed following the treatment of the plantlets with GABA. In addition, the GABA-treated plantlets were also subjected to a comparative transcriptomic and metabolomic analysis. The exogenous application of GABA significantly promoted growth and improved the quality of the blueberry plantlets. In total, 2,626 differentially expressed genes (DEGs) and 377 differentially accumulated metabolites (DAMs) were detected by comparison of the control and GABA-treated plantlets. Most of the DEGs and DAMs were involved in carbohydrate metabolism and biosynthesis of secondary metabolites. The comprehensive analysis results indicated that GABA may promote the growth of blueberry plantlets by promoting carbon metabolism and nitrogen assimilation, as well as increasing the accumulation of secondary metabolites such as flavonoids, steroids and terpenes.

Investigation into the Relationship between Spermidine Degradation and Phenolic Compounds Biosynthesis in Barley Seedlings under Ultraviolet B Stress.

Barley germination under ultraviolet B (UV-B) illumination stress induces effective accumulation of phenolic compounds in the barley. Spermidine can enhance the biosynthesis of phenolic compounds and alleviate the oxidative damage caused by UV-B. To better understand the function of spermidine, inhibitors of enzymes that are involved in the degradation of spermidine and the synthesis of gamma-aminobutyric acid (GABA), the product of spermidine degradation, were applied to barley germinated under UV-B treatment. The results showed a more severe oxidative damage, and a decrease in phenolic acid contents were observed when spermidine degradation was inhibited. However, GABA application did attenuate an increase in electrolyte permeability and MDA content caused by UV-B induced oxidative damage and improved the respiration rate. Meanwhile, GABA application can elevate the accumulation of phenolic compounds by ca. 20%, by elevating the activities of some key enzymes. Furthermore, the application of GABA, together with the inhibitor of spermidine degradation, can alleviate its suppression of the synthesis of phenolic acids, and resistance to UV-B stress. In conclusion, spermidine alleviated oxidative damage and enhanced the accumulation of phenolic compounds using its degradation product.

Resilient and sustainable production of peanut (Arachis hypogaea) in phosphorus-limited environment by using exogenous gamma-aminobutyric acid to sustain photosynthesis

Globally, many low to medium yielding peanut fields have the potential for further yield improvement. Low phosphorus (P) limitation is one of the significant factors curtailing Arachis hypogaea productivity in many regions. In order to demonstrate the effects of gamma-aminobutyric acid (GABA) on peanuts growing under P deficiency, we used a pot-based experiment to examine the effects of exogenous GABA on alleviating P deficiency-induced physiological changes and growth inhibition in peanuts. The key physiological parameters examined were foliar gas exchange, photochemical efficiency, proton motive force, reactive oxygen species (ROS), and adenosine triphosphate (ATP) synthase activity of peanuts under cultivation with low P (LP, 0.5 mM P) and control conditions. During low P, the cyclic electron flow (CEF) maintained the high proton gradient (∆pH) induced by low ATP synthetic activity. Applying GABA during low P conditions stimulated CEF and reduced the concomitant ROS generation and thereby protecting the foliar photosystem II (PSII) from photoinhibition. Specifically, GABA enhanced the rate of electronic transmission of PSII (ETRII) by pausing the photoprotection mechanisms including non-photochemical quenching (NPQ) and ∆pH regulation. Thus, GABA was shown to be effective in restoring peanut growth when encountering P deficiency. Exogenous GABA alleviated two symptoms (increased root-shoot ratio and photoinhibition) of P-deficient peanuts. This is possibly the first report of using exogenous GABA to restore photosynthesis and growth under low P availability. Therefore, foliar applications of GABA could be a simple, safe and effective approach to overcome low yield imposed by limited P resources (low P in soils or P-fertilizers are unavailable) for sustainable peanut cultivation and especially in low to medium yielding fields.

Gamma-aminobutyric acid (GABA) improves the cadmium phytoremediation capacity of Galinsoga parviflora Cav.

ABSTRACT Gamma-aminobutyric acid (GABA) is a signalling substance that related to the stress condition. To improve the cadmium (Cd) phytoremediation capacity of hyperaccumulator Galinsoga parviflora Cav., the effects of exogenous GABA on the Cd accumulation of G. parviflora were studied. The treatment of Cd (0.1 mg/L) decreased the biomass and photosynthetic pigment content of G. parviflora, indicating that Cd treatment produced stress to G. parviflora. Under Cd stress, exogenous GABA increased the biomass and photosynthetic pigment content of G. parviflora to some extent, and the applications of GABA at 1 and 2 g/L increased the shoot biomass by 10.36% and 28.83%, respectively, compared with Cd treatment. Exogenous GABA also increased the Cd content, bioconcentration factor, and Cd extraction of G. parviflora. The applications of GABA at 1 and 2 g/L increased the shoot Cd content by 13.39% and 16.53%, respectively, and increased the shoot Cd extraction by 25.25% and 49.83%, respectively, compared with Cd treatment. Therefore, GABA can alleviate Cd stress to G. parviflora and improve its phytoremediation capacity.

Effect of gamma-aminobutyric acid on resistance against stripe rust (caused by Puccinia striiformis f. sp. tritici) in wheat cultivars

Aim: The present study was undertaken to screen wheat cultivars for resistance against stripe rust and the improvement of resistance by exogenous gamma-aminobutyric acid (GABA) under field conditions and studying two contrasting cultivars for antioxidant related defense activities at 1, 2 and 4 d of GABA, Puccinia striiformis f. sp. tritici (Pst) and GABA+Pst treatments given to one-month-old seedlings. Methodology: Wheat cultivars (PBW723, PBW725, PBW677, PBW550, PBW343, PBW621, HD2967) were grown and exposed to Puccinia striiformis f. sp. tritici (Pst) and GABA+Pst in fields and studied for yield parameters. Subsequently, two cultivars found varying in resistance (PBW725 and HD2967) were analyzed for antioxidant enzymes in leaves and roots at 1, 2, and 4 day of GABA, Pst, and GABA+Pst and water as control given to 30 days old seedlings in the greenhouse. Results: Field analysis found that the most resistant cultivar PBW725 reduced vegetative growth but not yield compared to other resistant cultivars (PBW723 and PBW677) under Pst and improved both growth and yield under GABA+Pst. GABA+Pst improved yield parameters in other cultivars also. In defense analysis, superoxide dismutase (SOD), ascorbate peroxidase (APX) and glutathione-S-transferase (GST) increased in the leaves of PBW725 while only APX increased in HD2967 at 1 d of Pst. In roots also, SOD and GST increased 2-fold in PBW725 while only GST increased 1.3-fold in HD2967 at 1 d of Pst. There was persistence of catalase (CAT), monodehydroascorbate reductase (MDHAR), and dehydroascorbate reductase (DHAR) during Pst in the leaves of PBW 725 while CAT decreased at 4 d in HD2967. In roots also, CAT and MDHAR increased at 4 days of Pstin PBW725 while DHAR decreased in HD2967. Under GABA, cultivar differences were not significant. GABA+Pst improved deficient antioxidant enzymes in HD2967. Interpretation: Energy conservation and timely regulation of antioxidant enzymes during infection was utilized by PBW725 against stripe rust. GABA deficiency can be a reason for poor regulation of antioxidants in HD2967 under Pst. GABA application improved resistance against stripe rust in wheat. Key words: Antioxidant, Ascorbate, Gamma-aminobutyric acid, Glutathione, Stripe rust, Triticum aestivum

Bacillus amyloliquefaciens Increases the GABA in Rice Seed for Upregulation of Type I Collagen in the Skin

Biosynthesis of gamma-aminobutyric acid (GABA) can be achieved by naturally occurring microorganisms with the advantages of cost-effectiveness and safety. In this study, Bacillus amyloliquefaciens EH-9 strain (B. amyloliquefaciens EH-9), a soil bacterium, was used to promote the accumulation of GABA in germinated rice seed. Further, the topical application of supernatant from rice seed co-cultivated with soil B. amyloliquefaciens EH-9 can significantly increase the production of type I collagen (COL1) in the dorsal skin of mice. The knocking down of the GABA-A receptor (GABAA) significantly reduced the production of COL1 in the NIH/3T3 cells and in the dorsal skin of mice. This result suggests that topical application of GABA can promote the biosynthesis of COL1 via its interaction with the GABAA receptor in the dorsal skin of mice. In summary, our findings illustrate for the first time that soil B. amyloliquefaciens EH-9 elicits GABA production in germinated rice seed to upregulate the formation of COL1 in the dorsal skin of mice. This study is translational because the result shows a potential remedy for skin aging by stimulating COL1 synthesis using biosynthetic GABA associated with B. amyloliquefaciens EH-9.

Application of gamma-aminobutyric acid and nitric oxide on turfgrass stress resistance: Current knowledge and perspectives

Gamma-aminobutyric acid (GABA) is a nonprotein amino acid that is well recognized as an endogenous plant signaling molecule. Nitric Oxide (NO) is a signaling molecule that has diverse biological functions in plants. There has been increasing research evidence that elucidates the protective roles of GABA and NO in improving plant growth and abiotic stress resistance of turfgrass species through enhancing photosynthetic and antioxidant defense capacities, maintenance of membrane integrity, osmotic adjustment and ion hemostasis, and increasing gene and protein expressions and accumulation of certain metabolites. Furthermore, the crosstalk between GABA and NO for modulating stress response are of interests in recent years. This review summarizes the current research advances of the physiological and molecular mechanisms involved in GABA- and NO- mitigated abiotic stress effects and discusses knowledge gaps in exploiting role of GABA an NO in turfgrass stress resistance. The review aims at promoting future research work towards a deeper understanding of GABA and NO applications in enhancing turfgrass management, production, and environmental adaptation.

Production of gamma-aminobutyric acid (GABA) by Bacillus subtilis BBEL02 fermentation using nitrogen-rich industrial wastes as crude feedstocks

Industrial-scale fermentation of γ-aminobutyric acid (GABA) is often limited by high cost of the starting raw materials. Increasing commercial applications of GABA in various industries have urged the research on finding the alternative substrates for the GABA production. The effects of concentration of different types of carbon and nitrogen sources; concentration of monosodium glutamate (MSG) in the defined medium for GABA production using the newly isolated Bacillus subtilis BBEL02 were studied. The feasibility of corn steep liquor (CSL) and soybean hydrolysate (SBH) as the replacement of nitrogen sources in the fermentation media for GABA production was also investigated. Highest GABA content (10.9 gL−1) and productivity (3.7 gL−1d−1) were achieved with defined medium containing 1 % (w/v) glucose, 2 % (v/v) SBH and 5 % (w/v) MSG. Dissolved oxygen (DO) of 80 % in 2-L fermenter presented the highest productivity (4.2 gL−1d−1) and GABA concentration (12.5 gL−1), however DO of 50 % was preferred because of the lower rotation speed to prevent cells deterioration.

Exogenous Gamma-Aminobutyric Acid Application Induced Modulations in the Performance of Aromatic Rice Under Lead Toxicity.

Gamma-aminobutyric acid (GABA) is a non-protein amino acid and has a multi-functional role in abiotic stress tolerance. A pot experiment was conducted to assess the role of exogenous gamma-aminobutyric acid (GABA) application to modulate the growth, yield, and related physio-biochemical mechanisms in two aromatic rice cultivars, that is, Guixiangzhan (GXZ) and Nongxiang 18 (NX-18), under Pb toxic and normal conditions. The experimental treatments were comprised of Ck: without Pb and GABA (control), GABA: 1 mM GABA is applied under normal conditions (without Pb), Pb + GABA: 1 mM GABA is applied under Pb toxicity (800 mg kg−1 of soil), and Pb= only Pb (800 mg kg−1 of soil) is applied (no GABA). The required concentrations of GABA were applied as a foliar spray. Results revealed that Pb stress induced oxidative damage in terms of enhanced malondialdehyde (MDA), electrolyte leakage (EL), and H2O2 contents, while exogenous GABA application improved leaf chlorophyll, proline, protein and GABA contents, photosynthesis and gas exchange, and antioxidant defense under Pb toxicity in both rice cultivars. Moreover, glutamine synthetase (GS) and nitrate reductase (NR) activities were variably affected due to GABA application under Pb stress. The yield and related traits, that is, productive tillers/pot, grains/panicle, filled grain %, 1,000-grain weight, and grain yield were 13.64 and 10.29, 0.37% and 2.26%, 3.89 and 19.06%, 7.35 and 12.84%, and 17.92 and 40.56 lower under Pb treatment than Pb + GABA for GXZ and NX-18, respectively. Furthermore, exogenous GABA application in rice reduced Pb contents in shoot, leaves, panicle, and grains compared with Pb-exposed plants without GABA. Overall, GXZ performed better than NX-18 under Pb toxic conditions.

Exogenous Application of GABA Alleviates Alkali Damage in Alfalfa by Increasing the Activities of Antioxidant Enzymes

Alfalfa (Medicago sativa L.) is a widely grown and important forage crop. However, alkali stress is detrimental to alfalfa yield and nutritional quality. Gamma-aminobutyric acid (GABA) is a signaling molecule, it participates in and responds to metabolic regulation related to plant growth and development and stress. In this study, we clarify the effect of spraying alfalfa seedlings with GABA on the alkali tolerance of the seedlings. We determined that exogenous application of GABA at 75 mmol/L improved the resistance of alfalfa seedlings to alkali stress caused by exposure to 100 mmol/L NaHCO3, pH 8.5. Exogenous GABA significantly increased the chlorophyll content, the accumulation of soluble sugars in the plants, significantly decreased their relative electrical conductivity, malondialdehyde (MDA), superoxide anion (O2−) and hydrogen peroxide (H2O2) contents, and significantly increased the activities of the antioxidant enzymes catalase (CAT), superoxide dismutase (SOD), and peroxidase (POD). Exogenous GABA increased the activities of GAD and GABA-T, increased the content of glutamate and endogenous GABA, and regulated the expression of the genes MsGAD, MsGABA-T and MsGDH. In alfalfa plants that survived for a long time, compared to the control group, root length and fresh weight were significantly higher. Exogenous GABA had a positive effect on the resistance of alfalfa seedlings to alkali stress, and the effect was closely associated with GAD and GABA-T activity, glutamate content and the levels of endogenous GABA and antioxidants. This work provides a new method for the cultivation of early-stage alfalfa seedlings under low or moderate alkali stress conditions through the application of 75 mmol/L GABA.

Characterization of GABA-Transaminase Gene from Mulberry (Morus multicaulis) and Its Role in Salt Stress Tolerance.

Gamma-aminobutyric acid (GABA) has been reported to accumulate in plants when subjected to salt stress, and GABA-transaminase (GABA-T) is the main GABA-degrading enzyme in the GABA shunt pathway. So far, the salt tolerance mechanism of the GABA-T gene behind the GABA metabolism remains unclear. In this study, the cDNA (designated MuGABA-T) of GABA-T gene was cloned from mulberry, and our data showed that MuGABA-T protein shares some conserved characteristics with its homologs from several plant species. MuGABA-T gene was constitutively expressed at different levels in mulberry tissues, and was induced substantially by NaCl, ABA and SA. In addition, our results demonstrated that exogenous application of GABA significantly reduced the salt damage index and increased plant resistance to NaCl stress. We further performed a functional analysis of MuGABA-T gene and demonstrated that the content of GABA was reduced in the transgenic MuGABA-T Arabidopsis plants, which accumulated more ROS and exhibited more sensitivity to salt stress than wild-type plants. However, exogenous application of GABA significantly increased the activities of antioxidant enzymes and alleviated the active oxygen-related injury of the transgenic plants under NaCl stress. Moreover, the MuGABA-T gene was overexpressed in the mulberry hairy roots, and similar results were obtained for sensitivity to salt stress in the transgenic mulberry plants. Our results suggest that the MuGABA-T gene plays a pivotal role in GABA catabolism and is responsible for a decrease in salt tolerance, and it may be involved in the ROS pathway in the response to salt stress. Taken together, the information provided here is helpful for further analysis of the function of GABA-T genes, and may promote mulberry resistance breeding in the future.

Stimulating biolipid production from the novel alga Ankistrodesmus sp. by coupling salt stress and chemical induction

In the present research, the freshwater green alga Ankistrodesmus sp. EHY was isolated from Erhai Lake. To obtain high productivity of biomass and lipids, a joint strategy comprising salinity stress and chemical induction and two-stage cultivation was developed to improve the production of lipids. Coupling salinity stress and gamma-aminobutyric acid (GABA) or CaCl2 addition increased the lipid content to 56.47 ± 1.56% or 59.52 ± 0.00%, which was 1.24 or 1.31 times greater than that of the control, respectively (p < 0.05). The maximum energy yield was achieved under GABA and salt stress conditions of 95.78 kJ L−1. Further data revealed that the combined application of salt stress and GABA or CaCl2 increased the levels of cellular reactive oxidative species (ROS) and lipogenesis genes, accompanied by a further increase in lipids. The quality of the algal lipid-derived biodiesel was within the biodiesel quality ranges for advanced commercial standards. These results suggest that combined application of GABA or CaCl2 and salt stress can stimulate microalgae biolipid synthesis for the production of renewable biodiesel. This work proposes an efficient potential biotechnological method for biolipid production by a novel Ankistrodesmus sp. strain via combined induction of chemical and salt stress under two-stage cultivation.

Host Gamma-Aminobutyric Acid Metabolic Pathway Is Involved in Resistance Against Rhizoctonia solani.

Rhizoctonia solani is a highly destructive necrotrophic fungal pathogen having a diverse host range, including rice and tomato. Previously R. solani infection has been found to cause large-scale readjustment in host primary metabolism and accumulation of various stress-associated metabolites such as gamma-aminobutyric acid (GABA) in rice. In this study, we report upregulation of GABA pathway genes during pathogenesis of R. solani in rice and tomato. The exogenous application of GABA provided partial resistance against R. solani infection in both the hosts. Furthermore, by using the virus-induced gene silencing approach, we knocked down the expression of some of the tomato genes involved in GABA biosynthesis (glutamate decarboxylase) and GABA catabolism (GABA-transaminase and succinic semialdehyde dehydrogenase) to study their role in host defense against R. solani infection. The silencing of each of these genes increased disease susceptibility in tomato. Overall the results from gene expression analysis, exogenous chemical application, and gene silencing studies suggest that the GABA pathway plays a positive role in plant defense against necrotrophic pathogen R. solani.

Synergistic Effects of Melatonin and Gamma-Aminobutyric Acid on Protection of Photosynthesis System in Response to Multiple Abiotic Stressors

GABA (gamma-aminobutyric acid) and melatonin are endogenous compounds that enhance plant responses to abiotic stresses. The response of Vicia faba to different stressors (salinity (NaCl), poly ethylene glycol (PEG), and sulfur dioxide (SO2)) was studied after priming with sole application of GABA and melatonin or their co-application (GABA + melatonin). Both melatonin and GABA and their co-application increased leaf area, number of flowers, shoot dry and fresh weight, and total biomass. Plants treated with GABA, melatonin, and GABA + melatonin developed larger stomata with wider aperture compared to the stomata of control plants. The functionality of the photosynthetic system was improved in primed plants. To investigate the photosynthetic functionality in details, the leaf samples of primed plants were exposed to different stressors, including SO2, PEG, and NaCl. The maximum quantum yield of photosystem II (PS II) was higher in the leaf samples of primed plants, while the non-photochemical quenching (NPQ) of primed plants was decreased when leaf samples were exposed to the stressors. Correlation analysis showed the association of initial PIabs with post-stress FV/FM and NPQ. Stressors attenuated the association of initial PIabs with both FV/FM and NPQ, while priming plants with GABA, melatonin, or GABA + melatonin minimized the effect of stressors by attenuating these correlations. In conclusion, priming plants with both GABA and melatonin improved growth and photosynthetic performance of Vicia faba and mitigated the effects of abiotic stressors on the photosynthetic performance.

Assessing saffron response to salinity stress and alleviating potential of gamma amino butyric acid, salicylic acid and vermicompost extract on salt damage

Detailed information on response of saffron, one of the most economical medicinal plants, to high levels of saline (NaCl) water irrigation is not available. In this study, effect of spraying Gamma amino butyric acid (GABA), salicylic acid (SA) and vermicompost extract (VCE) on root structure, corm and flower production, K+ and Na+ allocation, physiological and photosynthesis aspects along with antioxidant enzymes activity of saffron were evaluated under saline water irrigation. The treatments consisted of adding four salinity doses to irrigation water (0, 5, 10 and 15 dS m−1 of NaCl) as main plot and four exogenous foliar applications (control, distilled water; GABA, 10 mM; SA, 1.5 mM and VCE, 5%) as subplot. The results illustrated that increasing root density; generating larger and heavier corms; and promoting Na+ exclusion and K+ accumulation were the main tolerance mechanisms which help saffron produce a satisfactory economical yield under salt stress conditions. All the foliar application treatments, especially VCE, could nullify the detrimental impacts of salinity. VCE remedied the nutrient deficiency caused by reducing soil osmotic potential and improved aerial K+/Na+ ratio in salinity conditions. Triggering antioxidant defense system was the most notable mechanism of GABA and SA that led to alleviation of adverse effect of salt stress. In conclusion, the results demonstrated that saffron can be introduced as a salt-tolerance crop and exogenous foliar application of VCE, GABA and SA are suggested for minimizing negative effects of salinity on saffron.

Foliar Application of Ascorbic Acid and Gamma Aminobutyric Acid Can Improve Important Properties of Deficit Irrigated Cucumber Plants (Cucumis sativus cv. Us)

Cucumber and other Cucurbitaceae plants have a high transpiration rate and sensitivity to water deficit stress. Ascorbic acid (AsA) and gamma aminobutyric acid (GABA) participate in a variety of plant processes and increase plant resistance to different stresses. The current study was aimed to assess the efficacy of the foliar application of AsA (100, 200 and 300 mg l−1) and GABA (20 and 40 mM) on growth, physiological parameters and water use efficiency related properties of cucumber plants under deficit irrigation (DI) strategy (0, 25 and 50%). Results showed that the highest values of measured morphological properties were recorded in plants treated with GABA at 40 mM and AsA at 100 mg l−1. The highest water use efficiency was observed in plants sprayed with GABA at 40 mM. Also, foliar spraying of GABA at 40 mM was the best treatment to improve the free proline content of leaves and the activity of antioxidant enzymes under drought stress conditions. Findings of this study showed that foliar application of AsA and GABA can be a useful and inexpensive treatment to improve morphological, physiological and water use efficiency related properties of cucumber plant under water deficit stress.

GABA reverses salt-inhibited photosynthetic and growth responses through its influence on NO-mediated nitrogen-sulfur assimilation and antioxidant system in wheat

Gamma-aminobutyric acid (GABA) is a newly recognized signaling molecule participating in physiological processes, growth, and development of plants under optimal and stressful environments. In the present reported research, we investigated the role of GABA in imparting salt stress tolerance in wheat (Triticum aestivum L.). Exposure of wheat plants to 100 mM NaCl resulted in increased oxidative stress, glucose content, nitric oxide (NO) production together with reduced growth and photosynthetic traits of plants. Contrarily, GABA application improved nitrogen (N) metabolism, sulfur (S) assimilation, ion homeostasis, growth and photosynthesis under salt stress. Additionally, GABA mitigated oxidative stress induced by salt stress with the increased ascorbate-glutathione cycle and proline metabolism. The study with NO inhibitor, c-PTIO [2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxy-3-oxide] in GABA experiment suggested that the impact of GABA on improvement of growth and photosynthesis under salt stress was mediated by NO and influenced N and S assimilation and antioxidant systems. The results suggested that the GABA has a significant potential in reversing the salt stress response in wheat plants, and GABA-mediated signals are manifested through NO.