Showing papers on "Gibberellic acid published in 2020"

Antagonistic regulation of the gibberellic acid response during stem growth in rice

Abstract: The size of plants is largely determined by growth of the stem. Stem elongation is stimulated by gibberellic acid1–3. Here we show that internode stem elongation in rice is regulated antagonistically by an ‘accelerator’ and a ‘decelerator’ in concert with gibberellic acid. Expression of a gene we name ACCELERATOR OF INTERNODE ELONGATION 1 (ACE1), which encodes a protein of unknown function, confers cells of the intercalary meristematic region with the competence for cell division, leading to internode elongation in the presence of gibberellic acid. By contrast, upregulation of DECELERATOR OF INTERNODE ELONGATION 1 (DEC1), which encodes a zinc-finger transcription factor, suppresses internode elongation, whereas downregulation of DEC1 allows internode elongation. We also show that the mechanism of internode elongation that is mediated by ACE1 and DEC1 is conserved in the Gramineae family. Furthermore, an analysis of genetic diversity suggests that mutations in ACE1 and DEC1 have historically contributed to the selection of shorter plants in domesticated populations of rice to increase their resistance to lodging, and of taller plants in wild species of rice for adaptation to growth in deep water. Our identification of these antagonistic regulatory factors enhances our understanding of the gibberellic acid response as an additional mechanism that regulates internode elongation and environmental fitness, beyond biosynthesis and gibberellic acid signal transduction. Stem growth in rice is regulated by an accelerator gene and a decelerator gene in parallel with gibberellic acid, and the opposite selection of these genes has led to adaptations to different environments.

Effect of exogenous application of IAA and GA3 on growth, protein content, and antioxidant enzymes of Solanum tuberosum L. grown in vitro under salt stress

Abstract: Indole-3-acetic acid (IAA) and gibberellic acid (GA3) are essential for the growth and development of plants. In the present study, the ameliorative potential of these phytohormones on growth, protein content, and antioxidant enzymes was investigated in in vitro-grown Solanum tuberosum L. cultivars ‘Cardinal’ and ‘Desiree’ under salt stress. A 4 × 3 factorial combination of 0, 40, 60, or 80 mM NaCl with 0, 7, or 14 μM IAA, or 0, 14, or 21 μM GA3, were added to Murashige and Skoog (MS) basal medium, followed by inoculation of nodal explants or callus cultures. The data for root and shoot number and length, number of nodes and leaves, fresh weight of plants, increase or decrease in fresh weight of callus cultures, total soluble protein, and superoxide dismutase (SOD) and peroxidase (POD) activities were recorded after 30 d. The growth of both callus cultures and nodal explants subjected to NaCl stress was substantially reduced compared with the control. Both IAA and GA3 successfully alleviated the harmful effects of salt stress on all of the growth parameters studied. Salt stress resulted in decreased protein content, which increased when the media also contained phytohormones. The activities of SOD and POD were increased with either IAA or GA3 under NaCl stress. Therefore, the exogenous application of both IAA and GA3 not only played a positive role in terms of in vitro potato growth but also significantly affected the biochemical parameters tested.

Molecular and Functional Characterization of CaNAC035, an NAC Transcription Factor From Pepper (Capsicum annuum L.).

Abstract: NAC (NAM, ATAF1/2, and CUC2) proteins are the plant-specific transcription factors (TFs) which are important in plant response to abiotic stresses. However, knowledge about the functional role that NACs play in pepper abiotic stress tolerance is limited. In this study, we isolated a NAC TF gene, CaNAC035, from pepper (Capsicum annuum L.), where the protein is localized in the nucleus and functions as a transcriptional activator. CaNAC035 expression is induced by low and high temperatures, osmotic stress, salt, gibberellic acid (GA), methyl-jasmonic acid (MeJA), salicylic acid (SA), and abscisic acid (ABA). To understand the function of CaNAC035 in the abiotic stress responsep, we used virus-induced gene silencing in pepper to knockdown the CaNAC035 and overexpressed the CaNAC035 in Arabidopsis. The results showed that pepper seedlings in which CaNAC035 was silenced, showed more damage than the control pepper plants after cold, NaCl, and mannitol treatments. Correspondingly increased electrolyte leakage, a higher level of malondialdehyde (MDA), H2O2, and superoxide radicals were found after cold treatments. CaNAC035-silenced seedlings exhibited lower chlorophyll content while CaNAC035-overexpressed Arabidopsis plants had higher germination rate and fresh weight after mannitol and NaCl treatments. We also reported 18 proteins that potentially interact with CaNAC035 and may participate in processes such as the stress response, resistance, and photosynthesis. Our results suggest that CaNAC035 is a positive regulator of abiotic stress tolerance in pepper which acts through multiple signaling pathways.

The Auxin Signaling Repressor IAA8 Promotes Seed Germination Through Down-Regulation of ABI3 Transcription in Arabidopsis.

Abstract: Seed germination is a complex biological process controlled by various regulators, including phytohormones. Among these, abscisic acid and gibberellic acid inhibit and promote seed germination, respectively. Many studies have addressed the biological roles of auxin in plant growth and development, but very few have considered its role in seed germination. Here, we identified a novel function of the auxin signaling repressor Aux/IAA8 during seed germination. The IAA8 loss-of-function mutant iaa8-1 exhibited delayed seed germination. The phenotype of iaa8-1 was restored by ectopic expression of IAA8. Interestingly, IAA8 accumulated to high levels during seed germination, which was achieved not only by increased protein synthesis but also by the stabilization of IAA8 protein. We also showed that IAA8 down-regulates the transcription of ABSCISIC ACID INSENSITIVE3 (ABI3), a negative regulator of seed germination. Our study, thus strongly suggest that the auxin signaling repressor IAA8 acts as a positive regulator of seed germination in Arabidopsis thaliana.

Rice GERMIN-LIKE PROTEIN 2-1 Functions in Seed Dormancy under the Control of Abscisic Acid and Gibberellic Acid Signaling Pathways.

Abstract: Seed dormancy is a natural phenomenon in plants. It ensures that seeds complete the grain-filling stage before germination and prevents germination in unsuitable ecological conditions. In this study, we determined the previously unknown function of the rice (Oryza sativa) gene GERMIN-LIKE PROTEIN 2-1 (OsGLP2-1) in seed dormancy. Using artificial microRNA and CRISPR/CAS9 approaches, suppression of OsGLP2-1 expression in rice resulted in the release of dormancy in immature seeds. Conversely, overexpression of OsGLP2-1 driven by the OsGLP2-1 native promoter led to greater seed dormancy. Seed scutellum-specific expression of OsGLP2-1 was increased by exogenous abscisic acid, but decreased with gibberellic acid treatment. We provide evidence that OsGLP2-1 is antagonistically controlled at the transcriptional level by ABA INSENSITIVE5 and GAMYB transcription factors. We conclude that OsGLP2-1 acts as a buffer, maintaining appropriate equilibrium for the regulation of primary dormancy during seed development in rice.

Gibberellic Acid Can Improve Seed Germination and Ornamental Quality of Selected Cyclamen Species Grown Under Short and Long Days

Abstract: Cyclamen species (swinebread spp.) are perennial herbaceous plants which belong to the Primulaceae family, widely used as medicinal or ornamental plants. Currently, gibberellic acid (GA3), an environmentally friendly bioregulator is widely used to enhance the productivity and phenotypic characteristics of multiple ornamental crops. A dual experiment was conducted to evaluate the influence of gibberellic acid (50, 100 or 150 mg/L), on germination earliness of seeds, along with growth and ornamental quality of selected Cyclamen species. Additionally, a greenhouse experiment with long and short sunlight photoperiod was conducted to evaluate its importance in the development of Cyclamen plants. Our results indicated that under short sunlight exposure, seeds germinated earlier than those kept in long sunlight photoperiod. Plants treated with foliar applications of GA3 exhibited higher plant height, leaf area, number of leaves, root length and tuber development. Significant differences were found in germination percentage (GP), mean germination time (MGT) and seedling vigor index (SVI), within different GA3 supplementation and greenhouse sunlight intensity (short and long days). In conclusion, our study suggests that seedling vigor and ornamental quality can be increased by GA3 application, an economic strategy for enhancing germination and growth of selected Cyclamen species.

Water Uptake and Germination of Caper (Capparis spinosa L.) Seeds

Abstract: Caper is a perennial deciduous sub-shrub that grows in almost all circum-Mediterranean countries. The specialized literature presents three possible dormancy types that can cause low germination of caper seeds: Physiological dormancy (PD), physical dormancy (PY), and combinational dormancy (PY + PD). We conducted three experiments to analyze the imbibition, viability, and germination of seeds of different ages, provenances, and the level of deterioration of the seed cover. None of the commercialized lots of standard seeds tested exceeded 6% germination, nor 35% viability, while the owned seeds reached 90% in both parameters, indicating that all viable seeds germinated. The seed moisture content along the soaking period followed the first two phases of the typical triphasic model of water uptake in seed germination: The imbibition and lag phases (phase I and II of germination, respectively). Seed hydration began through the hilar region. The fact that all viable owned seeds germinated, together with their moisture content being lower than that of standard seeds, indicated that caper seeds do not have a water-impermeable coat sensu stricto, i.e., they do not show PY; nevertheless, the need to use gibberellic acid to obtain high germination percentages, demonstrated the presence of PD.

The Role of Gibberellic Acid and Paclobutrazol on Oxidative Stress Responses Induced by In Vitro Salt Stress in Sweet Sorghum

Abstract: Gibberellic acid (GA3) application has been shown to affect salinity tolerance through modulating oxidative stress processes. Moreover, paclobutrazol (PBZ) as a GA3 biosynthetic inhibitor has been reported to mitigate salt stress in some plant species. In this study, we investigated how GA3 and its inhibitor, PBZ, reduced the negative effects of salt stress in leaves of sweet sorghum (Sorghum bicolor [L.] Moench cv. Sofra) by changing content of osmoprotectants and activity of ROS-scavenging enzymes. After germination, seedlings of sorghum were cultured in Hoagland solution containing sodium chloride (0, 100 and 200 mM NaCl) supplemented with GA3 and PBZ for 12 days. The results were analyzed using principal component analysis (PCA) to identify the best target(s) under salinity, GA3 and PBZ in sweet sorghum. Based on PCA, our findings showed that PBZ and GA3 treatments acted by different mechanisms under salinity. GA3 primarily affected the activity of superoxide dismutase (SOD), peroxidase (POD), glutathione reductase (GR), catalase (CAT), and glycine betaine (GB) contents under salinity, whereas PBZ treatment had significant influence on the activity of Δ1-pyrroline-5-carboxylate synthetase (P5CS), proline content, activity of CAT, GR, and total antioxidant capacity in leaves of sweet sorghum plants.

Micropropagation of Alocasia longiloba Miq and Comparative Antioxidant Properties of Ethanolic Extracts of the Field-Grown Plant, In Vitro Propagated and In Vitro-Derived Callus.

Abstract: In this study, an efficient micropropagation protocol was developed for A longiloba and the antioxidant properties of field-grown plant, in vitro-derived greenhouse-grown plant and in vitro-derived callus extracts were compared The A longiloba seeds tested using tetrazolium chloride salt exhibited 89% viability Due to poor germination capacity of A longiloba seeds, the seeds were treated with gibberellic acid (GA3) or sulfuric acid (H2SO4) The maximum seed germination of 87% was observed at 30% H2SO4 treatment after 1900 d, whereas GA3 treatment showed maximum germination of 53% after 22 d In vitro shoot multiplication was carried out using various types of cytokinins alone or in combination with auxin Among them, 6-benzyl amino purine (BAP) single treatment was found to be the best hormone The highest shoot-length (726 cm) and maximum number of shoots per explant (18) were recorded at 3-mg L-1 BAP For in vitro rooting, indole-3-acetic acid at 05-mg L-1 was found to be the optimum concentration Callus was induced using various types of auxins alone or in combinations with cytokinins The highest percentage of callus of 91 and fresh weight of 6 g was obtained with 3-mg L-1 IAA The plantlets produced in the current study were subjected to acclimatization The combination of topsoil and peat moss at 1:2 ratio was found to be the best soil media In this study, in vitro-derived callus extract showed the highest phenolic content (538 mg GAE), followed by extracts of field-grown plant parts, ie, fruit and petiole (504 and 300 mg GAE) while in vitro plant extract showed the lowest (98 mg GAE) Meanwhile, the highest flavonoids was recorded in petiole extract Comparative antioxidant activity study shows, in vitro-derived callus exhibited better DPPH-radical-scavenging activity (IC50: 0113-mg mL-1) whereas the extracts of petiole, fruit and in vitro plant showed 0126-, 0137- and 0173-mg mL-1, respectively At the same time, the fruit extract showed better (IC50: 0088-mg mL-1) ABTS radical scavenging activity than all extracts tested In conclusion, the in vitro-derived callus extract could be favored for high TPC and better DPPH scavenging activity Hence, the present study was conducted to establish an efficient micropropagation protocol and to compare the antioxidant activity of the field-grown plant, in vitro plant and in vitro derived callus extracts of A longiloba

Improved reproductive growth of euhalophyte Suaeda salsa under salinity is correlated with altered phytohormone biosynthesis and signal transduction

Abstract: Phytohormones are essential for plant reproductive growth. Salinity limits crop reproductive growth and yield, but improves reproductive growth of euhalophytes. However, little is known about the mechanisms underlying salinity's effects on plant reproductive growth. To elucidate the role of plant hormones in flower development of the euhalophyte Suaeda salsa under saline conditions, we analysed endogenous gibberellic acid (GA3,4), indoleacetic acid (IAA), zeatin riboside (ZR), abscisic acid (ABA), and brassinosteroids (BRs) during flowering in control (0 mM) and NaCl-treated (200 mM) plants. At the end of vegetative growth, endogenous GA3, GA4, ABA and BR contents in stems of NaCl-treated plants were significantly higher than those in controls. During flowering, GA3, GA4, IAA and ZR contents showed the most significant enhancement in flower organs of plants treated with NaCl when compared with controls. Additionally, genes related to ZR, IAA, GA, BR and ABA biosynthesis and plant hormone signal transduction, such as those encoding CYP735A, CYP85A, GID1, NCED, PIF4, AHP, TCH4, SnRK2 and ABF, were upregulated in S. salsa flowers from NaCl-treated plants. These results suggest that coordinated upregulation of genes involved in phytohormone biosynthesis and signal transduction contributes to the enhanced reproductive growth of S. salsa under salinity.

Salicylic acid ameliorates salinity tolerance in maize by regulation of phytohormones and osmolytes

Abstract: Salinity is one of the most widespread stresses responsible for water and soil pollution across the globe. Salicylic acid (SA) has a major role in defence responses against various abiotic stresses. In the current study, SA (0.05 mmol) influences were evaluated in mitigation of the negative impact of salinity (40 and 80 mmol NaCl) in the maize plant. NaCl stress-induced significant accumulation of organic osmolytes (total soluble sugars (TSS), total soluble protein (TSP), and proline) by 35.6, 66.2, and 89.2%, respectively, with 80 mmol NaCl. In addition, salinity is also responsible for the elevated accumulation of inorganic osmolytes (Na+ and Na+/K+ ratio) by 202.4% and 398.8%, respectively, and for the reduction in the K+ and Ca2+ levels by 48.6% and 58.9%, respectively, with 80 mmol NaCl. Moreover, salinity stress reduced phytohormones (indoleacetic acid (IAA) and gibberellic acid (GA3)) by 48.8% and 59.8%, respectively, with 80 mmol NaCl; however, abscisic acid (ABA) was increased by 340.5% with 80 mmol NaCl. Otherwise, SA application caused an additional enhancement in TSS, TSP, proline, K+, Ca2+, IAA, and GA3 contents but decreased the Na+, Na+/K+ ratio, and ABA to an appreciable level. In conclusion, SA pre-soaking mitigates the negative impact of NaCl toxicity in maize through the regulation of phytochromes and various organic and inorganic osmolytes, which may ameliorate salinity tolerance in maize.

Gibberellic Acid-Priming Promotes Fluoride Tolerance in a Susceptible Indica Rice Cultivar by Regulating the Antioxidant and Phytohormone Homeostasis

Abstract: Excessive utilization of groundwater for anthropogenic purposes has led to severe depletion of the water table, resulting in contamination of fluorides from the mineral bed. Irrigation of rice seedlings with such fluoride-infested water leads to high fluoride bioaccumulation and compromised growth physiology. In the present study, we showed that the priming of seeds with gibberellic acid 3 (GA) alleviated prolonged fluoride-induced toxicity in the fluoride-susceptible indica rice cultivar, IR-64 (grown in soil) by reducing the accumulation of the xenobiotic within the seedling biomass. The primed seeds showed improved percentage of germination during fluoride stress compared to the non-primed seeds. The stressed seedlings grown from the GA-primed seeds exhibited increased endogenous accumulation of GA and the auxin, indole-3-acetic acid which stimulated shoot and root growth and relative water content, compared to the stressed seedlings germinated from the non-primed seeds. GA-priming reduced the chlorophyll degradation, affected the homeostasis of the accessory pigments and lowered the electrolyte leakage during stress. Upon GA-priming, the fluoride-induced oxidative stress was ameliorated by an increase in proline, anthocyanin, flavonoid and total phenolic contents, reducing power, total antioxidant capacity and DPPH-radical scavenging activity. The altered activity of the antioxidative enzymes like catalase, ascorbate peroxidase and guaiacol peroxidase also enabled efficient H2O2 scavenging in the stressed plants germinated from the primed seeds. Thus, seed pre-treatment with GA promoted fluoride tolerance by activating the antioxidant machinery and elevating the endogenous level of the two most important classes of plant growth regulators, gibberellic acid and auxin.

Effect of Gibberellic Acid on Production of Biomass, Polyphenolics and Steviol Glycosides in Adventitious Root Cultures of Stevia rebaudiana (Bert.).

Abstract: In current study, the effect of gibberellic acid was tested for production of biomass, polyphenolics and Steviol glycosides in adventitious root cultures of Stevia rebaudiana. Adventitious cultures were induced from the roots of in vitro grown plantlets on Murashige and Skoog (MS) medium containing combination of gibberellic acid (GA3; 0.5, 1.0, 1.5 and 2.0 mg/L) and naphthalene acetic acid (NAA; 0.5 mg/L). Initially, a known mass of inoculum roots were shifted into suspension media augmented with various GA3 concentrations. The growth behavior of adventitious roots was recorded every 3 days for a period of 30 days. Maximum biomass biosynthesis (13.12 g/flask) was noticed in exponential phase on 27th day in the suspension containing 2.0 mg/L of GA3. Other GA3 concentrations also displayed optimum patterns of biomass accumulation as compared to the control. Adventitious roots were investigated for total phenolic content (TPC) and production (TPP), total flavonoid content (TFC) and production (TFP), and 1, 1-diphenyl-2-picrylhydrazyl (DPPH)-based antioxidant potential. Maximum phenolics (TPC 9.84 mg gallic acid equivalent (GAE)/g-dry weight (DW)) and TPP (147.6 mg/L), TFC (5.12 mg Quercitin equivalent (QE)/g-DW) and TFP (76.91 mg/L) were observed in 2.0 mg/L GA3 treated cultures. The same concentration of gibberellic acid enhanced antioxidant activity (77.2%). Furthermore, maximum stevioside (7.13 mg/g-DW), rebaudioside-A (0.27 mg/g-DW) and dulcoside-A (0.001 mg/g-DW) were observed in roots exposed to 2.0 mg/L GA3. This is the first report on the application of GA3 on biomass accumulation and secondary metabolite production in S. rebaudiana. The current study will be helpful to scale up the adventitious root cultures in bioreactors for the production of biomass and pharmaceutically important secondary metabolites.

Maturation and Conversion of Somatic Embryos Derived from Seeds of Olive (Olea europaea L.) cv. Dahbia: Occurrence of Secondary Embryogenesis and Adventitious Bud Formation.

Abstract: Maturation and conversion of somatic embryos are two crucial steps that hamper the development of efficient somatic embryogenesis systems in olive. Herein, a simple and efficient protocol for the maturation and conversion of olive somatic embryos is reported. Globular somatic embryos derived from seeds of cv. Dahbia were cultured on either half-strength olive (OM) or olive cyclic embryogenesis (ECO) media, with and without plant growth regulators (PGRs). The embryos reached the cotyledonary stage in 9 weeks, but those cultured on ECO medium containing 0.1 mg·L-1 6-(dimethylallylamino)purine (2iP), 0.1 mg·L-1 6-benzyladenine (BA) and 0.05 mg·L-1 indole-3-butyric acid (IBA) exhibited the largest sizes, with an average of 4.7 mm. Somatic embryo conversion into plantlets was evaluated using different culture media (half-strength OM or one-third strength Murashige and Skoog (MS)), light conditions (light or dark) and desiccation pretreatments. The highest rate of somatic embryo conversion (45%) was observed under a 16 h photoperiod on half strength OM medium containing 0.1 mg·L-1 gibberellic acid (GA3) and 0.1 mg·L-1 1-naphthalene acetic acid (NAA). The embryos that failed to germinate showed either necrosis, cotyledon greening with no further conversion, adventitious bud formation or secondary embryogenesis. The findings of this study will be beneficial for biotechnological applications in olive.

Some Physiological and Biochemical Mechanisms during Seed-to-Seedling Transition in Tomato as Influenced by Garlic Allelochemicals

Abstract: The effects of aqueous garlic extracts (AGEs), diallyl disulfide (DADS), and allicin (AAS) were investigated during seed-to-seedling transition of tomato. Independent bioassays were performed including seed priming with AGE (0, 100, and 200 µg∙mL-1), germination under the allelochemical influence of AGE, DADS, and AAS, and germination under volatile application of AGE. Noticeable differences in germination indices and seedling growth (particularly root growth and fresh weights) were observed in a dose-dependent manner. When germinated under 50 mM NaCl, seeds primed with AGE exhibited induced defense via antioxidant enzyme activities (superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT)), lipid peroxidation (malondialdehyde content (MDA)), and H2O2 scavenging. Enzyme-linked immunosorbent analysis (ELISA) of the endogenous phytohormones auxin (IAA), abscisic acid (ABA), cytokinin (ZR), and gibberellic acid (GA3) in the roots and shoots of the obtained seedlings and the relative expression levels of auxin-responsive protein (IAA2), like-auxin (LAX5), mitogen-activated protein kinase (MAPK7 and MPK2), respiratory burst oxidase homolog (RBOH1), CHI3 and SODCC1 suggested allelopathic functions in stimulating growth responses. Our findings suggest that garlic allelochemicals act as plant biostimulants to enhance auxin biosynthesis and transportation, resulting in root growth promotion. Additionally, the relative expressions of defense-related genes, antioxidant enzymes activities and phytohormonal regulations indicate activation of the defense responses in tomato seedlings resulting in better growth and development. These results, thus, provide a basis to understand the biological functions of garlic allelochemicals from the induced resistance perspective in plants.

Induction of growth and defense mechanism in rice plants towards fungal pathogen by eco-friendly coelomic fluid of earthworm

Abstract: Coelomic fluid (CF) of earthworms, Eudrilus eugeniae, collected by cold stress method (cold CF) was tested for its potential in different growth parameters such as seed germination, lengths of shoot, root and seedlings and vigor index in Oryza sativa L subsp indica Gibberellic acid (GA) was used as a control to compare with cold CF Rate of seed germination and length of roots were better in CF-treated seedlings Other growth parameters were improved by CF when compared to control, but lesser or closer to the levels induced by GA Bioassays with detached leaves from rice plants and the fungal pathogen Rhizoctonia solani revealed that the disease index was reduced in CF-treated rice plants Liquid chromatography and mass spectrometry (LC–MS)​ analysis of CF suggested the presence of compounds with pesticidal, insecticidal, antifungal and plant hormone properties Plant hormone derivative, indole-3-acetyl-L-valine, from CF of earthworms is reported here for the first time Our results provide knowledge on developing new environmentally safe compounds to improve agriculture from organic wastes The biological roles of metabolites in CF on growth parameters of rice and resistance towards R solani are discussed

Gibberellic Acid Modifies the Transcript Abundance of ABA Pathway Orthologs and Modulates Sweet Cherry (Prunus avium) Fruit Ripening in Early- and Mid-Season Varieties.

Abstract: Several phytohormones modulate ripening in non-climacteric fruits, which is triggered by abscisic acid (ABA). Gibberellins (GAs) are present during the onset of ripening in sweet cherry fruits, and exogenous gibberellic acid (GA3) application delays ripening, though this effect is variety-dependent. Although an ABA accumulation delay has been reported following GA3 treatment, the mechanism by which GA modulates this process has not been investigated at the molecular level in sweet cherry. Therefore, the aim of this work is to analyze the effect of GA3 on the fruit ripening process and the transcript levels of ABA pathway orthologs in two varieties having different maturity time phenotypes. The early-season variety had a rapid transition from yellow to pink fruit color, whereas pink color initiation took longer in the mid-season variety. GA3 increased the proportion of lighter colored fruits at ripeness in both varieties, but it produced a delay in IAD—a ripening index—only in the mid-season variety. This delay was accompanied by an increased transcript abundance of PavPP2Cs, which are putative negative regulators of the ABA pathway. On the other hand, the early-season variety had increased expression of PavCYP707A2—a putative ABA catabolic gene–, and reduced transcript levels of PavPP2Cs and SnRK2s after the GA3 treatment. Together these results show that GA modulates fruit ripening, exerting its action in part by interacting with the ABA pathway in sweet cherry.

Gibberellic Acid and Sulfur-Mediated Reversal of Cadmium-Inhibited Photosynthetic Performance in Mungbean (Vigna radiata L.) Involves Nitric Oxide

Abstract: Gibberellic acid (GA) and sulfur (S) have been known to modulate physiological processes of plants in normal and stressful conditions. Cultivars of mungbean (Vigna radiata L.), Pusa Vishal, PusaRatna, Pusa 9531, Ganga, and MH 318 were screened for photosynthetic S-use efficiency (p-SUE) and growth in presence of 200 mg Cd kg−1 soil. Pusa 9531 showed maximum p-SUE, growth, and Cd tolerance. The mechanism of 10 µM GA-induced alleviation of Cd stress in Cd tolerant cultivar Pusa 9531 grown with 100 mg S kg−1 soil (100S) or 200 mg S kg−1 soil (200S) was investigated. Plants receiving GA in presence of 100S maximally utilized available S and improved photosynthetic characteristics of plants through improvement in SUE and antioxidant metabolism and alleviated Cd stress; the addition of 200S was of no additional benefit. Such effects of GA and 100S in protection of photosynthetic performance and growth involved nitric oxide (NO), which was evidenced on the use of NO modulators: 100 µM SNP (sodium nitropruside; NO promoter) or 100 µM c-PTIO (2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide; NO scavenger). The application of SNP improved the mechanisms of N- and S-assimilation and antioxidant metabolism which helped in tolerance of plants to Cd stress. Moreover, c-PTIO supplementation to GA plus S reversed the positive effects of GA and S on photosynthesis and growth, signifying the involvement of NO in mechanisms induced by GA + S under Cd stress. The study provides the evidence that GA and NO interact and mechanisms induced by GA in presence of S were mediated by NO. The inter-relation of GA and NO may be used for augmenting photosynthesis and growth through utilization of S in mungbean grown under Cd stress.

Influence of Foliar-Applied Humic Acid and Some Key Growth Regulators on Sugar Beet ( Beta vulgaris L.) Under Drought Stress: Antioxidant Defense System, Photosynthetic Characteristics and Sugar Yield

Abstract: To assess the impact of humic acid and three potential growth regulators as salicylic acid (SA), gibberellic acid (GA3) and ascorbic acid (AsA) on sugar beet under drought stress, a field experiment as a split plot based on completely randomized block design was performed. The main plots comprised three watering regimes, well-watered, 60% field capacity (mild water stress) and 45% field capacity (severe water stress). Foliar application of humic acid, SA, GA3 and AsA was allocated into sub-plots. Both drought stress regimes caused a decline in root yield, sugar content, chlorophyll content, relative water content and leaf area index. In contrast, drought stress resulted in a marked rise superoxide dismutase, peroxidase and catalase activities as well as the levels of proline, glycine betaine, malondialdehyde and hydrogen peroxide in sugar beet plants. However, foliar application of humic acid, SA, GA3 and AsA reasonably increased the activities/levels of enzymatic and non-enzymatic antioxidants and vita organic osmolytes. The current findings suggest that exogenous application of humic acid is effective in tailoring the sugar plants to thrive well on drought-prone areas.

A review on role and use of gibberellic acid (GA3) in flower production

Abstract: The plant growth regulators consist of a large group of naturally occurring or synthetically produced organic chemicals and considered as helping tool in the modern production system of flowering plants. Plant growth regulators are being used by the commercial growers of ornamental plants as a part of cultural practice. Plant growth regulators have quicker impact on vegetative as well as flower yield of flowering crops. Among them, Gibberellic Acid (GA3) plays important role in flower production, quality and yield of the flower crops. The Gibberellic Acid (GA3) is a tetracyclic di-terpenoid compound and a plant hormone stimulating plant growth and development. GAs stimulate seed germination, trigger transitions from meristem to shoot growth, juvenile to adult leaf stage, vegetative to flowering, determines sex expression and grain development along with an interaction of different environmental factors viz., light, temperature and water. The production of flower with good quality flowers has greater importance. Their exogenous application helps to improve the different economically important and market desirable characteristics of flower plants. As it have various advantages like less time consuming to treat the plant and environment friendly. Use of growth regulators in flowering crops must be specific their action and toxicologically and environmentally safe. The physiological activities of flowering crops regulate by the application of growth regulators like GA3 has finally affect the growth and flower production in flowering crops. There are various factors contributing to the efficacy of plant growth regulators among them the method of application plays a key role in determining the effectiveness of plant growth regulators, as they can be effective if properly absorbed by plants. The physiological activities of flowering crops regulate by the application of growth regulators and finally affect the growth and flower production in flowering crops. In this review, we have summarised critically on the role and use of Gibberellic Acid (GA3) on flower production of commercial crops.

Revival of Ancient Marine Dinoflagellates Using Molecular Biostimulation.

Abstract: The biological processes involved in the preservation, viability, and revival of long-term dormant dinoflagellate cysts buried in sediments remain unknown. Based on studies of plant seed physiology, we tested whether the revival of ancient cysts preserved in century-old sediments from the Bay of Brest (France) could be stimulated by melatonin and gibberellic acid, two molecules commonly used in seed priming. Dinoflagellates were revived from sediments dated to approximately 150 years ago (156 ± 27, 32 cm depth), extending the known record age of cyst viability previously established as around one century. A culture suspension of sediments mixed with melatonin and gibberellic acid solutions as biostimulants exhibited germination of 11 dinoflagellate taxa that could not be revived under controlled culture conditions. The biostimulants revived some dinoflagellates from century-old sediments, including the potentially toxic species Alexandrium minutum. The biostimulants showed positive effects on germination on even more ancient cysts, showing dose-dependent effects on the germination of Scrippsiella acuminata. Concentrations of 1, 10, and 100 µM melatonin and gibberellic acid promoted germination. In contrast, 1,000 µM solutions, particularly for melatonin, drastically decreased germination, suggesting a potential noxious effect of high doses of these molecules on dinoflagellate revival. Our findings suggest that melatonin and gibberellic acid are involved in the stimulation of germination of dinoflagellate cysts. These biostimulants can be used to germinate long-term stored dinoflagellate cysts, which may promote studies of ancient strains in the resurrection ecology research field.

A New Endophytic Fusarium Oxysporum Gibberellic Acid: Optimization of Production Using Combined Strategies of Experimental Designs and Potency on Tomato Growth under Stress Condition.

Abstract: This study reports the potential of the endophytic fungi identified as a Fusarium oxysporum to produce gibberellic acid (GA3). The GA3 production was confirmed by high performance liquid chromatography. To improve the production of this phytohormone under solid state fermentation (SSF), successive optimization strategies were used. Firstly, Plackett-Burman design was applied for screening medium components and culture condition. Under the optimized condition, GA3 yield (7.14 g/kg) was 2.62-fold higher than by the use of the initial condition (2.72 g/kg). The concentration of the most influential parameters and their interaction were optimized with a Box-Behnken experimental design. The optimized condition led to a 1.14-fold enhancement in GA3 production, reaching 8.16 g/kg. The GA3 crude extract obtained by SSF was then used to study its ameliorative role on adverse salinity effect on tomato plants (Solanum lycopersicum L.). The interactive effects of different GA3 concentrations were examined on morphological and physiological parameters of tomato plants. The application of GA3 (10-6 M) under salt stress condition (100 mM) was found to improve growth and physiological parameters including plant height, total chlorophyll, starch, and proline contents. The exogenous application of GA3 is a potent strategy to reverse abiotic stress that affect the agricultural productivity and limit plant growth and yield.

Metconazole on Inhibition of Gibberellin Biosynthesis and Flowering Management in Mango

Abstract: Gibberellins have been shown to suppress floral development in mango, thus farmers have used growth retardants, especially paclobutrazol, to inhibit gibberellin biosynthesis, but in many countries such as Brazil, this is the unique registered molecule, which affects sustainability of the mango industry. The objective of this study was to evaluate the effect of metconazole on gibberellin biosynthesis inhibition and carbohydrate accumulation in ‘Palmer’ mango grown in semi-arid conditions. The experiment was accomplished from 2015 to 2017 in an experimental orchard located in Petrolina, Pernambuco, Brazil. The experimental design were randomized blocks with five treatments, five replications and three plants per replication. The treatments consisted of metconazole (0, 0.7, 1.0 or 1.3 g) and paclobutrazol (1.0 g) application per linear meter of plant canopy. According to the results, metconazole efficiently inhibits gibberellin biosynthesis in mango, but it affects AG1 + AG3 (Gibberellic Acid) and AG4 differently. Therefore, metconazole can potentially be used on mango flowering management, but further studies are required to determine specific management practices.

Isolation and evaluation of the plant growth promoting rhizobacterium Bacillus methylotrophicus (DD-1) for growth enhancement of rice seedling

Abstract: Bacillus methylotrophicus has been demonstrated to promote growth of various plants, whereas the promoting effect of B. methylotrophicus on rice growth has been rarely reported. In this study, B. methylotrophicus DD-1, capable of efficiently promoting the growth of rice, was isolated from the root soil of rice plants. The isolate exhibited potassium-solubilizing (1.18 mg/L), Indole-3-acetic acid (IAA) (87.26 mg/L), Gibberellic acid (GA) (25.91 mg/L) and Siderophore production activity (52.32%). As indicated from the result, plant growth parameters (e.g., dry weight, tiller number, root and shoot length) of rice seedlings treated with the isolate DD-1 were more effective than those of the control group in pot and soilless culture experiments. Moreover, the adsorption capacity of rice roots which were soaked in the bacterial suspension of isolate increased with the increase in concentration and absorption time. In sterilized and unsterilized soil, conformation of root colonization activity by bacterial isolate established by its nearer existence to the rice root. Thus, the B. methylotrophicus DD-1 enhances plant growth promotion by multifarious growth promoting and root colonization traits, thereby augmenting potassium level in soil. Henceforth, the potential bacterium could be exploited for the development of biological fertilizer, leading towards sustainable agronomy.

Seed priming with gibberellic acid rescues chickpea ( Cicer arietinum L.) from chilling stress

Abstract: Chickpea is sensitive to low temperature stress, especially during germination and stand establishment. Present study was planned to rescue the chickpea seedlings from chilling stress through seed priming with gibberellic acid. A study comprising of two chickpea cultivars (cv.) viz. Cagatay (a chilling tolerant cultivar: CTC) and Akcin (a chilling sensitive cultivar: CSC) in combination with 0, hydropriming, 5 µM, 10 µM, 15 µM, 20 µM gibberellic acid (GA3) seed priming treatments was tested in completely randomized design under chilling temperature. Primed and unprimed seeds were sown at 9 ± 0.5 °C day temperature for 14 h and 7 ± 0.5 °C night temperatures for 10 h. Final emergence percentage (FEP) in both cultivars was noted higher in 10 µM GA3 seed priming. Coefficient of uniformity of emergence (CUE) was increased and time taken to 50% emergence (E50) was shorten with the application of 5 or 15 µM GA3. Mean emergence time (MET) was reduced in both cultivars in 20 µM GA3 seed treatment. Emergence energy (EE) and emergence index (EI) of CTC were increased in 15 µM GA3. In CSC 5 µM GA3, seed treatment was most productive treatment under low temperature. Higher doses of GA3 seed treatments in CSC were proved very effective in maintaining high relative water contents and low electrolyte leakage. Plant height, root length and number of flowers were also increased in GA3 primed treatments. In conclusion, seed priming with GA3 can be used in chickpea for good stand establishment, crop growth, reducing electrolyte leakage and maintaining high relative water contents.