Maryam Haghighi; Atena Sheibanirad
Abstract
Introduction: Plants are constantly faced with abiotic and biotic stresses during their whole life. Abiotic stresses are various adverse environmental factors, including drought, high salinity, heavy metals, cold or heat shock, and ozone. Resulting in dehydration and osmotic stress, drought has caused ...
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Introduction: Plants are constantly faced with abiotic and biotic stresses during their whole life. Abiotic stresses are various adverse environmental factors, including drought, high salinity, heavy metals, cold or heat shock, and ozone. Resulting in dehydration and osmotic stress, drought has caused a dramatic reduction in crop production globally. Grafting can reduce the content of Malondialdehyde (MDA); prevent the accumulation of reactive oxygen species (ROS); increase activities of antioxidant enzymes; and maintain fresh and dry weights, grain yield, and relative water content in a variety of plants in response to drought stress. On the other hand, a range of abiotic and biotic elicitors can confer tolerance to drought stress in plants. Grafting of herbaceous fruit vegetables can reduce detrimental effects of biotic and abiotic challenges and cultural practices. Grafting can increase yield of cucurbits, initiate shoot growth, aid in resistance against nematodes and viruses, withstand high and low temperatures, improve nutrient and water absorption, resist against high concentration of salt, drought and waterlogging stresses. Grafting elite commercial cultivars onto selected vigorous rootstocks is a special method of adapting plants to counteract environmental stresses. Grafting is currently regarded as a rapid alternative tool to the relatively slow breeding methodology for increasing the environmental-stress tolerance of fruiting vegetables. Potential approach to reduce losses in production and improve water use efficiency under drought conditions in high-yielding genotypes would be to graft these varieties onto proper rootstocks capable of reducing the effect of water stress on the shoot and to increase tolerance to abiotic stresses. Cucumber (Cucumis sativus L.) is one of the main greenhouse vegetable crops widely grown in Saudi Arabia. The total greenhouse area for cucumber production in 2013 was 2605 hectares produced 236,087 tons. Major factor influencing growth and yield of cucumber is water quantity. The effects of different rootstocks on plant growth, yield, fruit quality and water consumption in cucumber was studied. The highest yield was obtained from 9075 (19.02 kg m2), which was 24.5 and 23.5% higher than in the non-grafted and self-grafted treatments, respectively. The plant height also increased with the use of rootstocks. The increase in the dry weights of the leaves and fruits depended on rootstocks. They concluded that grafting improved plant growth and yield depending on the rootstock genotype. Grafting has the potential to be as a strategy to increase the tolerance of plants to promote water use efficiency (WUE). The present study was aimed to evaluate the grafting biochemical and physiological effects on inducing drought stress resistance in cucumber. Materials and Methods: This experiment was conducted in complete randomized design with three replications and treatments are included grafted and ungrafted plants, and water potential level 0 (control), -0.4 and -0.8 MP. The Isfahan endemic cucumber specious as a scion with the hole method grafted on Ferro rootstock. The physiological and growth traits were measured. Photosynthesis (stomata conductance, photosynthesis, water use efficiency), growth (root and stem growth), and antioxidants (SOD, POD, protein) parameters, and transpiration were measured. Results and Discussion: Result indicated that grafting with increasing root nutrient absorption and its development drought stress resistance improved. Although, grafting reduced potassium content. Grafting and the interaction of rootstock ×scion impressed many morphological and physiological characteristics. Under stress condition, some features improved plant water relationship, growth and development. Gas exchange indices like photosynthesis, transpiration and stomatal conductance were lower in grafted plant compare to ungrafted plants. Proline content was significantly increased in grafted treatments compare to ungrafted ones. Higher potassium under -0.8 MP in grafted plants showed the maintenance osmotic stability and potassium hemostasis were the draught stress mechanism in resistant rootstocks. Conclusion: Finally, grafting as an efficient method to increase cucumber yield and improve drought resistance recommend. These results suggest that the use of drought tolerant Cucurbita rootstock can improve cucumber photosynthetic capacity under drought stress and consequently crop performance. The results revealed that grafted plants had better vegetative growth than ungrafted (control) ones. Furthermore, photosynthetic parameter, antioxidant activity and fresh and dry weight of stem and leaves were improved, but grafting had no significant effect on fruit quality and yield. In conclusion it is recommended that grafting procedure in some crops include cucumber should be done only after assuring the benefits and risks of grafted seedlings.
Bahareh Ghorbani; Zahra Pakkish
Abstract
Introduction: Chilling injury (CI) is the primary postharvest problem of orange (Citrus sinensis L.) and many other horticultural crops during storage. Washington Navel orange fruits are susceptible to CI during storage below 5°C, and the main CI symptoms are surface pitting, browning, discoloration ...
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Introduction: Chilling injury (CI) is the primary postharvest problem of orange (Citrus sinensis L.) and many other horticultural crops during storage. Washington Navel orange fruits are susceptible to CI during storage below 5°C, and the main CI symptoms are surface pitting, browning, discoloration and decay. Several promising methods have been developed to alleviate CI symptoms of orange fruit. These include postharvest physical treatments with UV-C, modified atmosphere packaging, temperature conditioning, and chemical treatments with plant growth regulators. Oxidative stress from excessive reactive oxygen species (ROS) has been associated with appearance of chilling damage in fruits. The oxidation of ROS is due to their reaction with numerous cell components coursing a cascade of oxidative reactions and consequent inactivation of enzymes, lipid peroxidation, protein degradation, and DNA damage. Aerobic organisms have evolved well-developed defense systems to establish a fine-tuned balance between ROS production and removal plants are protected against ROS effects by a complex antioxidant system. This involved both lipid soluble antioxidant (α- tocopherol and carotenoids) and water soluble reductants (glutathion and ascorbate) and enzymes, such as catalase (CAT), ascorbate peroxidase (APX), superoxide dismutase (SOD) and peroxidase (POD). Previous studies have shown that there is a positive relationship between the antioxidant enzymes activity and the chilling tolerance in harvested fruits. Nitric oxide (NO) is an important signaling molecule involved in many plant physiological processes. It has also been indicated that NO protects plant cells against oxidative stress by reducing ROS accumulation. When exogenously applied, NO has been shown to result in an improved chilling tolerance and reduced incidence of chilling injury in several fruits. The objectives of this study were to evaluate the effects of NO on chilling injury, lipid peroxidation content, peroxide hydrogen content, and the induction of antioxidant enzymes in Washington Navel orange (Citrus sinensis L.) fruit during storage at 5±1°C.
Materials and Methods: Washington Navel orange (Citrus sinensis L.) fruits were harvested at commercial maturity from a commercial orchard in Kerman, Iran, and transported to the laboratory on the same day. Orange fruits were treated with 0.25 and 0.5 mM nitric oxide for 5 min and then stored at 5±1°C and relative humidity of 85-90 % for 5 months. No nitric oxide use was considered as control. The experiment was arranged in completely randomized design (CRD) with three replicates. Characteristics such as chilling injury, total soluble solids, titratable acidity, pH, ascorbic acid, and activity of antioxidant enzymes (peroxidase and catalase) were evaluated in the present experiment.
Results and Discussion: The results showed that use of nitric oxide in fruits reduced significantly chilling injury, ion leakage, lipid peroxidation and hydrogen peroxide compared to control, though it increased activity of antioxidant enzymes. According to these results, unlike organic acids which decreased in treated and non-treated fruits, total soluble solids, ascorbic acid and pH of the fruits increased during storage, however, nitric oxide treatment reduced the rate of changes, be either reducing or increasing, in the mentioned parameters compared to control. So, fruits treated with 0.5 mMol nitric oxide showed the highest effect on the reduction of chilling injury.
In the present study, the results indicated that NO significantly reduced CI of orange fruits during storage at 5±1 °C. NO has been applied to reduce the development of chilling injury symptoms in a number of horticultural crops. Thus NO has the potential of application in postharvest treatment by alleviating chilling injury and maintaining quality, and the aim of this study was to determine how NO alleviates the anti-oxidative systems, probably one of the mechanisms of improved chilling tolerance, of orange fruit during chilling stress. This indicates that the chilling tolerance of orange fruit was also enhanced by postharvest treatment with NO. Lipid peroxidation and protective enzyme systems are often evaluated in studies of plant mechanisms under various stresses. Low temperature disrupts the balance of active oxygen species metabolism, leading to their accumulation and destruction of scavenging enzymes such as catalase and peroxidase. In the present study, exogenous per-treatment with nitric oxide at 0.25 and 0.5 mM significantly decreased the lipid peroxidation content and electrolyte leakage of cold stored orange fruit compared to untreated fruits. The level of H2O2 was maintained by NO treatment, which led to an increase in chilling tolerance. It has been reported that the improvement of chilling tolerance in harvested horticultural crops is related to the enhancement in activates of antioxidant enzyme. Researchers found that chilling-tolerant mandarins have a higher antioxidant enzyme activity than the chilling-sensitive ones. A number of postharvest treatments that induce chilling tolerance and alleviate chilling injury also enhanced antioxidant enzyme activity. However, to the best of our knowledge, this is the first paper reporting the beneficial effects of NO on CI of postharvest orange fruits. In this study, there was a continuous increase in peel and pulp lipid peroxidation content in all fruits, but the application of NO significantly delayed the increase of lipid peroxidation. Moreover, the change in membrane permeability (revealed by H2O2 content) showed trends similar to lipid peroxidation content; in other words, peel and pulp H2O2 content increased with storage duration, but NO markedly delayed the increase. NO has been considered to be involved in a network of interacting signal transduction pathways, which regulate defense responses to abiotic stress. The detoxification of ROS is dependent on antioxidant enzymes such as CAT and POD. The increase in these enzymes’ activity contributes to the adaptation of plants to cold stress and ameliorates oxidative damage such as lipid peroxidation (lipid peroxidation increase as indicator) and H2O2 content.
Conclusion: In conclusion, application of NO reduced CI of oranges stored at 5±1°C and maintained oranges quality as well. The chilling injury, lipid peroxidation, and peroxide hydrogen were significantly reduced by NO treatment especially at 0.5 mM. Induced cold resistance by NO treatment may be due to the stimulation of antioxidant enzymes, and protection against membrane oxidative damage, decreased lipid peroxidation and H2O2 content in orange fruits. These results may have implications for the use of NO in managing postharvest CI of other subtropical fruits stored at low temperatures.
Fateme Hasanvand; Abdolhossein Rezaeinejad; Mohammad Feizian
Abstract
Introduction: Scented geranium (Pelargonium graveolens) is a perennial plant of the family Geranium (Geraniaceae). Although CaCl2 at higher concentrations than NaCl in the soils and ground water in many areas of the word, most studies have been based on experiments that NaCl is the predominant salt. ...
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Introduction: Scented geranium (Pelargonium graveolens) is a perennial plant of the family Geranium (Geraniaceae). Although CaCl2 at higher concentrations than NaCl in the soils and ground water in many areas of the word, most studies have been based on experiments that NaCl is the predominant salt. Relatively few studies have focused on the effects of CaCl2 on plant growth and physiology. Silicon (Si) is considered as an essential element in several crops enhancing growth and alleviating different biotic and abiotic stresses. In this study, the role of Si in alleviation the deleterious effects of salinity on geranium have been studied.
Materials and Methods: This experiment was conducted in spring-summer 2014 in research greenhouse situated on the Faculty of Agriculture, Lorestan University, Khorramabad, Iran. The greenhouse temperature was 16.5–37.5 ◦C and relative humidity of greenhouse was 30–80%. Terminal stem cuttings with five nodes were obtained from mother plants in the same greenhouse and placed in a sand substrate for rooting in April. Uniform rooted cuttings were then transplanted into plastic pots (22 cm diameter and height) filled with sand substrates and grown hydroponically. Transplanting was done in May and one plant per pot was cultivated. Cultivated plants were irrigated with Hoagland’s medium electrical conductivity (EC) 1.8 dS/m, (pH) 5.8 twice a day. Experiment was arranged as factorial based on a completely randomized design with five replications. Factors consisted of daily application of 1.8, 4 and 6 ds/m CaCl2 and weekly application of 0, 0.5 and 1 mM silicic acid in nutrient solution. Plants were harvested in November. In this research some characteristics include the number of leaf, leaf area, photosynthetic pigments (chla, chlb. Total chl, carotenoids), MDA, EL, RWC, proline, number of stomata in surface unit of leaf, density of stomata and stomata index and antioxidant enzyme include CAT and POD measured.
Results and Discussion: In current study salinity decreased the number of leaf and leaf area and Si increased these characteristics. In general, decrease in the leaf area can result in a reduction in size of individual leaf of plants, decrease in the production of leaves and fall the old leaves. It also reduce the growth rate of leaf in salinity which causes osmotic effect around the roots (rhizosphere). Over time, the rate of cell division and elongation decreased, and finally this changes leads to decrease in the final size of leaf. In this study, salinity increased electrolyte leakage and the use of silicic acid prevents electrolyte leakage. Probably saturation of phospholipids with increasing salinity increased, as a result the fluidity of membrane decreased and finally increased the electrolyte leakage, silicic acid absorbed in plant and deposited in the cell membrane, causing the silica hardened. This causes in stress condition, cell membrane maintains stability and significantly reduced the amount of electrolyte leakage. In this study application Si in various concentrations under salinity stress brought a significant decrease in MDA compared with salinity alone. Salinity increased the MDA and EL so that application of1 mM silicic acid decreased EL to 16.7 and 11.9 percent plants grown in 4 and 6 dS/m EC, respectively, compared with controls. Application of 1 mM silicic acid decreased the MDA to 23.6 and 35 percent plants grown in 4 and 6 dS/m EC, respectively, compared with controls. Therefore, the present results indicate that Si can effectively ameliorate membrane lipid peroxidation, thus protecting plants from oxidative stress. Salinity affected on leaf anatomy and chloroplast ultrastructure, photosynthesis also affected by these factors. Reduction in chlorophyll at height salinity levels due to chloroplast destructive. The results showed that salinity decreased the density and stomatal index in plants and silicic acid increased these characteristics. Salinity decreased the RWC and antioxidant enzymes and application of silicic acid improved them. Increase in salinity increased the leaf proline and application of silicic acid alone in plant on stress decreased it.
Conclusion: Overall, the results of present research showed that high EC induced by CaCl2 negatively affected geranium growth, and weekly application of 1 mM silicic acid alleviated the destructive effects of stress and in high salinity the positive effect of silicic acid is more than in low salinity.
