Ethylene Accumulation Research Articles

Ethylene works as a possible regulator for the rootlet elongation and transcription of genes for phosphorus acquisition in cluster roots of Lupinus albus L.

ABSTRACT White lupin (Lupinus albus L.) plants are tolerant plants under phosphorus (P)deficiency. They form unique morphological roots, so-called cluster roots (CRs) under P deficiency. CRs contribute to P absorption by the expansion of the root surface area and P mobilization activities. Previous research has implied the involvement of several hormonal functions in CR formation. Ethylene is a key regulator responsible for the modification of root architecture and P acquisition in response to low P in plants. However, understanding the effect of ethylene on CR morphogenesis is not enough. Here, the focus was on the effects of ethylene on CR morphology and gene expression for P acquisition. First, a reanalysis of public RNA-Seq data indicated that the gene expression for ethylene synthesis was induced during CR maturation. In turn, the 10-days application of an ethylene synthesis inhibitor, CoCl2, and an ethylene precursor, ACC, to CR formed in hydroponic culture without P was performed. CR morphology, transcript levels of the genes related to P acquisition, and citrate concentration in roots were determined. The results indicated that the elongation of rootlets in CR was promoted in a Co2+ concentration-dependent manner, suggesting that ethylene is responsible for the arrest of rootlet elongation. mRNA accumulation for acid phosphatases, phosphate transporters, citrate synthases, and a putative citrate transporter increased in ACC-treated immature CR, suggesting that ethylene induces the transcription of genes for P acquisition. Additionally, the trend of citrate concentration in roots among treatments was similar to that in the expression of citrate synthases, supporting that ethylene accumulation promotes citrate synthesis. The roles of the arrest of rootlet elongation and regulation of gene expressions for P acquisition are considered independent functions of ethylene. It was concluded that ethylene works as a possible regulator for the rootlet elongation and transcription of genes for P acquisition in CRs, although further studies are required to elucidate the molecular mechanisms of the arrest of rootlet elongation and transcriptional regulation.

Thidiazuron Promotes Leaf Abscission by Regulating the Crosstalk Complexities between Ethylene, Auxin, and Cytokinin in Cotton.

Thidiazuron (TDZ) is widely used as a defoliant to induce leaf abscission in cotton. However, the underlying molecular mechanism is still unclear. In this study, RNA-seq and enzyme-linked immunosorbent assays (ELISA) were performed to reveal the dynamic transcriptome profiling and the change of endogenous phytohormones upon TDZ treatment in leaf, petiole, and abscission zone (AZ). We found that TDZ induced the gene expression of ethylene biosynthesis and signal, and promoted ethylene accumulation earlier in leaf than that in AZ. While TDZ down-regulated indole-3-acetic acid (IAA) biosynthesis genes mainly in leaf and IAA signal and transport genes. Furthermore, the IAA content reduced more sharply in the leaf than that in AZ to change the auxin gradient for abscission. TDZ suppressed CTK biosynthesis genes and induced CTK metabolic genes to reduce the IPA accumulation for the reduction of ethylene sensitivity. Furthermore, TDZ regulated the gene expression of abscisic acid (ABA) biosynthesis and signal and induced ABA accumulation between 12–48 h, which could up-regulate ABA response factor genes and inhibit IAA transporter genes. Our data suggest that TDZ orchestrates metabolism and signal of ethylene, auxin, and cytokinin, and also the transport of auxin in leaf, petiole, and AZ, to control leaf abscission.

Cucurbitaceae COld Peeling Extracts (CCOPEs) Protect Plants From Root-Knot Nematode Infections Through Induced Resistance and Nematicidal Effects.

With nematicides progressively being banned due to their environmental impact, an urgent need for novel and sustainable control strategies has arisen. Stimulation of plant immunity, a phenomenon referred to as “induced resistance” (IR), is a promising option. In this study, Cucurbitaceae COld Peeling Extracts (CCOPEs) were shown to protect rice (Oryza sativa) and tomato (Solanum lycopersicum) against the root-knot nematodes Meloidogyne graminicola and Meloidogyne incognita, respectively. Focusing on CCOPE derived from peels of melon (Cucumis melo var. cantalupensis; mCOPE), we unveiled that this extract combines an IR-triggering capacity with direct nematicidal effects. Under lab conditions, the observed resistance was comparable to the protection obtained by commercially available IR stimuli or nematicides. Via mRNA sequencing and confirmatory biochemical assays, it was proven that mCOPE-IR in rice is associated with systemic effects on ethylene accumulation, reactive oxygen species (ROS) metabolism and cell wall-related modifications. While no negative trade-offs were detected with respect to plant growth or plant susceptibility to necrotrophic pests or pathogens, additional infection experiments indicated that mCOPE may have a predominant activity toward biotrophs. In summary, the presented data illustrate a propitious potential for these extracts, which can be derived from agro-industrial waste streams.

Expression Analysis of Mitogen-Activated Protein Kinases (MAPKs) Gene Family in Grapevine Berries

Plants, as sessile living organisms, are dependent on signalling mechanisms. Mitogen-activated protein kinases (MAPKs) are a highly conserved gene family that take a role in switching an extracellular signal into an intercellular signal. Ripening-related processes in non-climacteric fruits are not as well understood as in climacteric fruits. In this regard, studying MAPKs in grape berries during developmental stages may lead to a better understanding of physiological interactions during commercially relevant stages, such as pigmentation, ripening, and phenolics accumulation in the berries. Each MAPK cascade involves three or four MAPK proteins that facilitate signal transduction by phosphorylation of downstream targets. We examined the relative expression of VvMAP2Ks and VvMAP4Ks in berries at two-weekly intervals, from flowering to over-ripening. Expression analysis of 5 MAP2Ks and 7 MAP4Ks suggested that both gene families may play an active role in development of berries. Expression of VvMAP2K1 showed a correlation with abscisic acid (ABA) and ethylene accumulation. Moreover, the expression pattern of VvMAP2K2 and VvMAP2K3 shows a correlation with auxin, and ABA accumulation respectively. Furthermore, VvMAP2K4 may have a role in berry size increment and halting stomatal development. In addition, VvMAP2K5 may play a role in floral organ development. VvMAP4Ks expression pattern moves them forward to be excellent markers for monitoring the effect of for instance climate changerelated stress on berry development.

DA-6 improves sunflower seed vigor under Al3+ stress by regulating Al3+ balance and ethylene metabolic

Aluminum (Al3+) stress restricts plant seed germination and seedling growth seriously. Here, the sunflower “S175″ variety was used to explore the technique of improving seed vigor under Al3+ stress and investigate the effect of diethyl aminoethyl hexanoate (DA-6) on physiological characteristics in sunflower seeds during germination under Al3+ stress. The results showed that 3.0 mmol·L−1 Al3+ treatment significantly suppressed the sunflower seed germination and seedling growth. Al3+ stress significantly increased Al3+ content and secretion rates of citric and malic acids in sunflower seeds during germination. Besides, endogenous ethylene content was increased in Al3+-treated seeds. DA-6 serves as a positive signal to regulate the sunflower seed germination under Al3+ stress. Moreover, DA-6 enhanced the activities of malic dehydrogenase, citrate synthase, and isocitrate dehydrogenase, up-regulated the expressions of organic acid transport-related genes (ALMT and MATE), resulting in reduced accumulation of Al3+. Furthermore, exogenous DA-6 mitigated excessive accumulation of ethylene by decreasing the 1-aminocyclopropane-1-dihydrodipicolinate synthase activity and related-gene expression. However, DA-6 treatment had no effect on abscisic acid or gibberellin metabolism in sunflower seeds under Al3+ stress. These results confirmed that DA-6 application enhanced the germination capacity through induction of the synthesis and transport of malic and citric acids, and suppression of the excessive accumulation of endogenous ethylene, thus contributing to alleviate Al3+ toxicity in sunflower seeds.

Hydrogen cyanamide enhances flowering time in tea oil camellia (Camellia oleifera Abel.)

Appropriate flowering time is one of the most important traits for oilseed production and crop yield in tea oil camellia (Camellia oleifera Abel.). It secures the availability of pollinators and balances the growth period after flowering with respect to cold winter temperatures and rainfall. However, the effective regulator of flowering time and its mechanisms in C. oleifera are not clearly understood. This study demonstrates that hydrogen cyanamide (HC), rather than gibberellin A3, gibberellin A4+7, thidiazuron, or 6-benzylaminopurine, acts as a potentially effective agent to promote flowering time by ~12 days. Accumulation of indole acetic acid, ethylene, salicylic acid, and reactive oxygen species (ROS) in floral buds of C. oleifera was significantly increased by HC treatment. Transcriptome analysis suggested that exogenous HC application promoted flowering via regulating genes involved in auxin metabolism, ethylene-MAPK (mitogen-activated protein kinase) signaling, and ROS metabolism. These results demonstrate that HC can advance flowering by enhancing cell expansion, cell cycle progression, and flower development in floral buds. These findings help understand the role of HC in flowering regulation in autumn/winter-flowering perennials and provide new insights into the potential utilization of HC as a flower inducer in C. oleifera cultivation.

The phytotoxicity mechanism of florpyrauxifen-benzyl to Echinochloa crus-galli (L.) P. Beauv and weed control effect

Weeds infest rice causing high yield losses, leading to the increasing use of herbicides for weed control. However, many weeds have evolved resistance to common commercial herbicides, including penoxsulam, metamifop and quinclorac. This study investigated the weed control effect and the phytotoxicity mechanism of florpyrauxifen-benzyl, a novel synthetic auxin herbicide registered for weed management in rice fields in China. The greenhouse study showed that florpyrauxifen-benzyl was highly efficient (GR50 < 6 and GR90 < 15 g a.i ha−1) at controlling 10 weed species commonly found in rice fields, including penoxsulam- and quinclorac- resistant(R) biotypes of Echinochloa Beauv. and bensulfuron-methyl-R biotype of Ammannia arenaria. The typical plant hormone content showed that following florpyrauxifen-benzyl treatment, indole-3-acetic acid (IAA) production changed only slightly at 12 h, while abscisic acid (ABA) production increased with time in the treated group, whose content was significantly higher than that of the control. Besides, ethylene biosynthesis was stimulated by florpyrauxifen-benzyl, ethylene production, 1-aminocyclopropane-1-carboxylic acid (ACC) content, and 1-aminocyclopropane-1-carboxylate synthase (ACS) and 1-aminocyclopropane-1-carboxylate oxidase (ACO) activities, which evidently increased in the treated group, and ethylene peaked at 36 h. For the antioxidant enzyme activities and malondialdehyde (MDA) content in the treated group, results showed that MDA content continuously increased with time and was greater than that in the untreated group at 48 h and 72 h, superoxide dismutase (SOD) activity changed with exposure time and was significantly higher in the treatment group than the control at 48 h. A similar phenomenon was observed in peroxidase (POD) activity, which reached a peak at 48 h, and no distinct difference in catalase (CAT) activity was observed among groups except for the higher activity in the treated groups than control at 36 h and 48 h. Our results showed that that the stimulation ethylene biosynthesis and accumulation of ABA and reactive oxygen species (ROS) play important roles in the phytotoxicity mechanism of florpyrauxifen-benzyl in plants. Our findings demonstrate the potential of florpyrauxifen-benzyl to provide an alternative weed management strategy for rice fields.

Preharvest fumigation of 1-Methylcyclopropene, aminoethoxyvin-ylglycine, chlorine dioxide and nitric oxide for improving postharvest quality of durian (Durio zibethinus) fruit

1-Methylcyclopropene, aminoethoxyvinylglycine, chlorine dioxide and nitric oxide were widely applied as ethylene synthesis inhibitors for crops at pre-harvest stages for various purposes. Durian (Durio zibethinus) was a seasonal fruit commonly cultivated in tropical regions. Durian was highly perishable at ambient condition due to its high respiration rate and ethylene accumulation. Preharvest treatment was considered as a promising strategy to regulate some physiological behaviors of durian during postharvest storage. This research was conducted during 2020 at Soc Trang Nanotech laboratory, Vietnam to evaluate the effectiveness of preharvest fumigation at dose 200 μL/L at 14 days before harvesting with 1-Methylcyclopropene (1-MCP), aminoethoxyvinylglycine (AVG), chlorine dioxide (ClO2) and nitric oxide (NO) on quality of durian fruit. After harvesting, the treated fruits were kept at 4°C for 28 days. In 7 day-interval, sample was taken to evaluate respiration rate, ascorbic acid content, glutathione content and ascorbic peroxidase activity. Results showed that 1-MCP-treated durian had the lowest respiration rate (101.24±1.27 mg CO2/kg/h) while maintained the highest ascorbic acid content (21.73±0.22 mg/100 g), glutathione content (29.30±0.11 μmol/kg) and ascorbic peroxidase activity (2.31±0.02 U/g) at the end of 28 days of storage. Preharvest treatment by 1-MCP significantly enhanced quality of durian fruit in an extended stability.

Melatonin Relieves Ozone Stress in Grape Leaves by Inhibiting Ethylene Biosynthesis.

Ozone (O3) stress severely affects the normal growth of grape (Vitis vinifera L.) leaves. Melatonin (MT) plays a significant role in plant response to various abiotic stresses, but its role in O3 stress and related mechanisms are poorly understood. In order to understand the mechanism of MT in alleviate O3 stress in grape leaves, we perform a transcriptome analyses of grapes leaves under O3 stress with or without MT treatment. Transcriptome analysis showed that the processes of ethylene biosynthesis and signaling were clearly changed in “Cabernet Sauvignon” grapes under O3 and MT treatment. O3 stress induced the expression of genes related to ethylene biosynthesis and signal transduction, while MT treatment significantly inhibited the ethylene response mediated by O3 stress. Further experiments showed that both MT and aminoethoxyvinylglycine (AVG, an inhibitor of ethylene biosynthesis) enhanced the photosynthetic and antioxidant capacities of grape leaves under O3 stress, while ethephon inhibited those capacities. The combined treatment effect of MT and ethylene inhibitor was similar to that of MT alone. Exogenous MT reduced ethylene production in grape leaves under O3 stress, while ethephon and ethylene inhibitors had little effect on the MT content of grape leaves after O3 stress. However, overexpression of VvACO2 (1-aminocyclopropane-1-carboxylate oxidase2) in grape leaves endogenously induced ethylene accumulation and aggravated O3 stress. Overexpression of the MT synthesis gene VvASMT1 (acetylserotonin methyltransferase1) in tobacco (Nicotiana tabacum L.) alleviated O3 stress and reduced ethylene biosynthesis after O3 stress. In summary, MT can alleviate O3 stress in grape leaves by inhibiting ethylene biosynthesis.

Gelatin-TiO2-coated expanded polyethylene foam nets as ethylene scavengers for fruit postharvest application

The efficacy of polyethylene foam nets coated with gelatin-TiO2 photocatalytic nanocomposite to postpone the climacteric fruit ripening was evaluated. The gelatin-TiO2 nanocomposite was deposited on the foam nets by dip-coating and used to degrade ethylene produced by papayas. Fruit treated with TiO2 photocatalysis showed an ethylene accumulation 60 % less than the control experiment fruit after four days under UV-A light. The photocatalytic degradation of ethylene produced by papayas over four days caused an effective delay of their ripening. It was characterized by the respiration rate reduction during the climacteric peak, absence of scalds and superficial fungi growth and more remarkable preservation of green color and firmness than control samples. The results showed that nanocomposite foam nets degraded ethylene under UV-A light and postponed the fruit ripeness and quality changes.

TINY BRANCHED HAIR functions in multicellular trichome development through an ethylene pathway in Cucumis sativus L.

The fruit trichomes of Cucurbitaceae are widely desired in many Asian countries and have been a key determinant of cucumber (Cucumis sativus L.) cultivar selection for commercial production and breeding. However, our understanding of the initiation and development of cucumber trichomes is still limited. Here, we found that the cucumber TINY BRANCHED HAIR (TBH) gene is preferentially expressed in multicellular trichomes. Overexpression of CsTBH in tbh mutants restored the trichome phenotype and increased the percentage of female flowers, whereas silencing of CsTBH in wild-type plants resulted in stunted trichomes with a lower rate of female flowers. Furthermore, we provide evidence that CsTBH can directly bind to the promoters of cucumber 1-Aminocyclopropane-1-Carboxylate Synthase (CsACS) genes and regulate their expression, which affects multicellular trichome development, ethylene accumulation, and sex expression. Two cucumber acs mutants with different trichome morphology and sex morphs compared with their near-isogenic line further support our findings. Collectively, our study provides new information on the molecular mechanism of CsTBH in regulating multicellular trichome development and sex expression through an ethylene pathway.

Dichromate-induced ethylene biosynthesis, perception, and signaling regulate the variance in root growth inhibition among Shaheen basmati and basmati-385 rice varieties.

Heavy metals, including a hexavalent form of chromium (Cr(VI)) increasing accumulation in agricultural soil, cause a significant reduction in quality, yield, and growth of rice varieties worldwide. Screening for the selection of tolerant varieties is essential for conventional and molecular breeding. Shaheen basmati (SB) and basmati-385 (B-385) rice varieties, a subspecies of indica, show different sensitivity to Cr(VI), but the underlying mechanisms of this different sensitivity remain elusive. In the current study, we examine the sensitivity of SB and B-385 based on the root, which is the primary organ that encounters water and soil containing Cr(VI), elongation assay, and ethylene's possible role (a stress-responsive phytohormone) in the process. Our results show that SB's seedlings exhibit hypersensitivity as a higher root elongation inhibition than B-385 under different Cr(VI) concentrations. Hypersensitive SB consistently expresses a higher level of ethylene biosynthesis and signaling-related genes than B-385. Moreover, ethylene signaling antagonist (silver, Ag) and biosynthesis inhibitor (aminoethoxy vinyl glycine, AVG) alleviate the difference in Cr(VI)-induced root growth inhibition between SB and B-385, respectively. Taken together, we conclude that ethylene mediates difference in sensitivity based on the difference in root growth inhibition in different rice varieties. The difference in Cr(VI)-induced root growth inhibition in SB and B-385. (A) Root growth of SB is slightly more as compared to B-385 in control conditions in the Hoagland solutions. (B) Seedlings of SB showed hypersensitivity to 200 μM Cr(VI) compared to B-385 in terms of primary root growth inhibition, which was higher in SB than B-385. Interestingly, Cr(VI)-induced relative transcript level of ethylene biosynthesis, perception, and signaling-related genes was significantly higher in hypersensitive SB than B-385. Current results in association with previous literature show that Cr(VI)-induced ethylene biosynthesis is regulating Cr(VI)-induced ethylene perception, signaling, and associated Cr(VI)-induced ethylene-mediated primary root growth inhibition. Conclusively, the difference in ethylene quantities in both varieties mediates the difference in root growth inhibition between SB and B-385 (C and E). The difference in Cr(VI)-induce root growth inhibition between SB and B-385 was significantly alleviated by ethylene signaling inhibitor (10 μM Ag, as AgNO3) and ethylene biosynthesis inhibitor (10 μM AVG) treatment in the presence of 200 μM Cr(VI), respectively. (D) Ethylene biosynthesis precursor (10 μM ACC) treatment-mediated induced root growth inhibition difference between SB and B-385 was not significant, which may be because of enough quantity of the Cr(VI)-mediated ethylene accumulation or unknown limiting factor. Arrows mean addition and an increase in expression, and T-line means suppression or inhibition. The width of the pointers (arrows) is proportional to the gene expression level.

Modifying the effect of stressed spring wheat seeds on intact ones

Spring wheat seeds react to the effect of stress factors of various natures with a nonspecific adaptive reaction, accompanied by intense emission of stress ethylene in trace amounts during the entire time, while. On the one hand, they remain viable, and on the other hand, have mechanical, radiation-chemical and temperature damage. Damaged air-dry seeds are not able to regenerate damaged organs and tissues and, being in a state of chronic stress, permanently induce ethylene biosynthesis. The effect of stressed seeds on intact ones is achieved remotely when they are stored together in the air environment and are blocked by active aeration, air-insulating materials and a decrease in temperature. The stronger the damaging effect on seeds is caused by the stress factor, the more intense is the accumulation of stress ethylene. An increase in the duration of exposure of intact by stressed seeds is accompanied by a more pronounced physiological modifications in seedlings of intact seeds with a sequential change in time in their stimulation of the initial growth processes and a sharp deterioration in sowing qualities.

AgNO3 improved micropropagation and stimulate in vitro flowering of rose (Rosa x hybrida) cv. Sena

Abstract Rose is one of the most important cut flower in the world. Rose micropropagation was used for production of clonal and disease-free plantlets and to breeding purposes. However, many important rose cultivars showed physiological disorders as early-leaf senescence and very low multiplication rate under in vitro conditions. Our hypothesis is that these symptoms were associated with high sensibility of these cultivars to ethylene accumulation on in vitro environment. The rose cv. Sena was in vitro cultivated under different concentrations of AgNO3 and two light sources, LED and fluorescent lamps, as a way to investigate in vitro similar symptoms to ethylene accumulation. AgNO3 at 1.0-2.0 mg L-1 solved the main in vitro physiological disorders observed in this rose cultivar. Also, AgNO3 stimulated induction of 50% of rose shoots to in vitro flowering at 2.0 mg L-1. Higher concentrations also resulted in flowering induction, but with imperfect flower development.

Promotion of tomato growth by the volatiles produced by the hypovirulent strain QT5-19 of the plant gray mold fungus Botrytis cinerea

Our previous study identified a hypovirulent strain QT5-19 of Botrytis cinerea, the causal agent of the plant gray mold disease, and found that QT5-19 can produce volatile organic compounds (VOCs) with high antifungal activity and high control efficacy against B. cinerea. However, impact of the QT5-19 VOCs on plant growth remains unknown. This study was conducted to investigate the impact of the QT5-19 VOCs on tomato growth, and to elucidate the mechanisms for the plant growth-promoting (PGP) activity of the QT5-19 VOCs. Results showed that compared to the control treatment, the QT5-19 VOCs significantly (P < 0.05) promoted tomato growth, and the PGP activity of the QT5-19 VOCs acted in dose- and time-dependent manners. Results also showed that the values of photosynthetic assimilation, stomatal conductance and transpiration, water use efficiency and chlorophyll content in the treatments of the QT5-19 VOCs were significantly (P < 0.05) higher than the corresponding values in the control treatment. The QT5-19 VOCs up-regulated expression of the genes for expansins (EXP2, EXP9 and EXP18), IAA (SlIAA1, SlIAA3 and SlIAA9), cytokinins (SlCKX1) and gibberellins in leaves and/or roots, whereas down-regulated expression of the gene ACO1 for ethylene in both organs. Moreover, enhanced accumulation of auxins and decreased accumulation of ethylene were observed in tomato roots in the treatment of the QT5-19 VOCs, compared to the control treatment. These results suggest that the QT5-19 VOCs probably promote tomato growth through improving photosynthesis and biosynthesis of expansins and IAA, and reducing ethylene biosynthesis. This study suggests that QT5-19 is a versatile biocontrol control agent.

Silver nanoparticles improved explant disinfection, in vitro growth, runner formation and limited ethylene accumulation during micropropagation of strawberry (Fragaria × ananassa)

One of the common problems in strawberry (Fragaria × ananassa) micropropagation is the vitrification phenomenon (succulent plantlets, brittle stems, yellow leaves, etc.) leading to the reduction of plantlets quality and low survival rate in the greenhouse. In this study, the effects of silver nanoparticles (AgNPs) on explant disinfection, in vitro growth (shoot multiplication, and root formation), runner formation as well as ethylene accumulation during micropropagation of strawberry were investigated. The results showed that leaf explants treated with 200 mg/L AgNPs solution for 20 min was more effective in explant disinfection and shoot regeneration than using 1 g/L HgCl2. In addition, AgNPs stimulated the growth of shoot and plantlet and as well shortened the duration of root formation (4 days) as compared to those in control without AgNPs during micropropagation. Besides, AgNPs reduced the ethylene gas accumulation in the culture’s vessels of shoots (0.66 ppm) and plants (0.06 ppm) compared to controls (1.77 ppm; 0.15 ppm; respectively). Moreover, AgNPs combination with culture period (5; 10 or 15 days) effect root formation stage and acclimatization in the greenhouse. The plantlets that cultured on MS medium supplemethed with 0.5 mg/L AgNPs during 10 days showed higher survival rate (93.33%) after 15 days as well as runner formation per plant (8.00 runners) after 60 days in greenhouse than those in control. AgNPs improved explant disinfection and in vitro growth. AgNPs improved runner formation in the greenhouse. AgNPs limited ethylene accumulation during micropropagation.

Synergistic effect of calcium chloride and 1-Methylcyclopropene on storage of watermelon (Citrullus lanatus (Thunb.) Matsum. &amp; Nakai

Watermelon (Citrullus lanatus (Thunb.) Matsum. &amp; Nakai was a climacteric variety with a high respiration rate and ethylene accumulation. Therefore the fruit matures and softeness quickly during post-harvest period. Calcium chloride was popularly utilized as stabilizing agent. 1-methylcyclopropene (1-MCP) has been known to be highly effective inhibitor of ethylene reaction. This research evaluated the synergistic effect of CaCl2 and 1-methylcyclopropene (1-MCP) treatment to weight loss, firmness, total soluble solid, carotenoid, ascorbic acid and decay rate of watermelon during storage. Results showed that a combination of 2.5% CaCl2 and 0.6 ppm 1-MCP in 20 min of immersion could extend watermelon shelf life for 15 days. After 15 days of ambient storage, the weight loss (1.43±0.02 %), firmness (4.38±0.00 N), total soluble solid (13.60±0.01 oBrix), carotenoid (16.31±0.02 µg/100g), ascorbic acid (13.36±0.03 mg/100g), decay rate (0.47±0.02 %) were clearly presented. Meanwhile, the treatment of 2.5% CaCl2 alone showed the weight loss (2.11±0.02 %), firmness (3.03±0.02 N), total soluble solid (10.83±0.02 oBrix), carotenoid (12.97±0.03 µg/100g), ascorbic acid (9.57±0.02 mg/100g), decay rate (2.14±0.01 %). The incorporation of CaCl2 and 1-MCP created a synergistic effect on the improved quality of watermelon fruit during ambient storage.

The effect of silver nanoparticles on the limitation of ethylene gas and hydrolytic enzymatic activity in micropropagation of rose (Rosa hybrida L. 'Baby love')

Micropropagation of rose (Rosa hybrida L. ‘Baby Love’) often encounter some abnormal phenomena such as yellow and abscission leaf, hyperhydricity, etc. These phenomena effect on the quality of shoots cultured in vitro as well as the survival rate of plantlets after transferred to greenhouse. This is due to the accumulation of ethylene in culture vessel, which leads to an increase in enzyme activity of cellulase and pectinase resulted in disrupting the cell wall binding and inducing organ abscission. In this study, the effect of silver nanoparticles (AgNPs) to overcome these abnormal phenomena as well as its effect on the growth and development of shoots and plantlets in rose cultured in vitro were evaluated. The results showed that after 6 weeks of shoot culture, the medium supplemented with 2 ppm AgNPs was the most suitable for in vitro shoot multiplication with the highest number of shoots/explant (6.67 shoots), shoot height (3.06 cm), fresh weight (451.00 mg), dry weight (58.33 mg), SPAD (32.28) and dry mass ratio(12.33%). Adding 3 ppm AgNPs into in vitro rooting medium may improve the growth and develop involve in plant height (3.06 cm), number of leaves (6.33), leaf length (1.50 cm), leaf width (1.50 cm), fresh weight (137.67 mg), dry weight (13.00 mg), number of roots (4.33), SPAD (39.37), dry mass ratio (9.40%) of rose plantlet after 4 weeks of culture. After treatment with AgNPs, the abnormal phenomena including ethylene gas accumulation (0.30 ppm), cellulase enzyme activity (0.14 UI/mL) and pectinase enzyme activity (0.40 UI/mL) was reduced compare with the other treatments and the control. In addition, the high survival rate (93.33%) of plantlets was also observed after 4 weeks transferred to greenhouse. On the other hand, the treatment with 5 ppm AgNPs also induced early rose in vitro flowering; however, when using AgNPs at high concentrations (7 ppm) inhibited growth, development, toxicity and even death of explants.

The role of ACC deaminase producing bacteria in improving sweet corn (Zea mays L. var saccharata) productivity under limited availability of irrigation water

Accumulation of stress ethylene in plants due to osmotic stress is a major challenge for the achievement of optimum sweet corn crop yield with limited availability of irrigation water. A significant increase in earth’s temperature is also making the conditions more crucial regarding the availability of ample quantity of irrigation water for crops production. Plant growth promoting rhizobacteria (PGPR) can play an imperative role in this regard. Inoculation of rhizobacteria can provide resistance and adaptability to crops against osmotic stress. In addition, these rhizobacteria also have potential to solve future food security issues. That's why the current study was planned to examine the efficacious functioning of Pseudomonas fluorescens strains on yields and physiological characteristics of sweet corn (Zea mays L. var saccharata) under different levels of irrigation. Three irrigation levels i.e., 100% (I100 no stress), 80% (I80), and 60% (I60) were used during sweet corn cultivation. However, there were four rhizobacteria strains i.e., P. fluorescens P1, P. fluorescens P3, P. fluorescens P8, P. fluorescens P14 which were used in the experiment. The results showed that severe water stress (60% of plant water requirement) decreased chlorophyll a, chlorophyll b, and total chlorophyll contents, Fv/Fm ratio and nutrients uptake. A significant increase in F0, Fm, proline, total soluble sugars, catalase (CAT) and peroxidase (POX) activity led to less ear yield and canned seed yield. Combination of four strains significantly increased the yield traits of sweet corn i.e., ear and (44%) and canned seed yield (27%) over control. The highest promoting effect was observed in the combination of four strains treatment and followed by P1 strain in reducing the harmful effects of drought stress and improving sweet corn productivity. However, P14 gave minimum improvement in growth and yield indices under limited availability of water. In conclusion, combination of four strains inoculation is an efficacious approach for the achievement of better yield of sweet corn under osmotic stress.

Methyl jasmonate alleviates the reduced release of aroma‐related esters in ‘Nanguo’ pears by regulating ethylene biosynthesis and signal transduction

SummaryCryopreserved fruits usually develop symptoms, which affects the release of aroma. Our study investigated the impact of exogenous methyl jasmonate (MeJA) upon the synthesis of aromatic esters in ‘Nanguo’ pears after cold storage. It found that exogenous MeJA enhanced ethylene accumulation via improving the activity of 1‐aminocyclopropane‐1‐carboxylic‐acid (ACC) synthase (ACS) and ACC oxidase (ACO) and the expression levels of PuACS1 and PuACO1. After cryopreservation for 90 days, the ester aroma of ‘Nanguo’ pears was effectively improved by MeJA during normal temperature shelf life. In addition, the expression of PuERS1, PuETR1, PuEIN4, PuEIN2 and PuERF1 in MeJA‐treated fruits were obviously increased. Therefore, we infer that the influence of MeJA on production of aroma‐related esters in ‘Nanguo’ pears is closely connected with ethylene biosynthesis and signal transduction, namely increase activity of ACS and ACO, and upregulation of the expression level of PuACS1, PuACO1, PuERS1, PuETR1, PuEIN2, PuEIN4 and PuERF1.