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.
Maryam Haghighi; Atena Sheibanirad
Abstract
Introduction: Soil salinity is a global problem that affects approx. 20 % of irrigated land and reduces crop yields significantly. Since, salinity is one of the most important abiotic stress and limiting factor for plant growth all around the world. It is necessary to find some way to ameliorate these ...
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Introduction: Soil salinity is a global problem that affects approx. 20 % of irrigated land and reduces crop yields significantly. Since, salinity is one of the most important abiotic stress and limiting factor for plant growth all around the world. It is necessary to find some way to ameliorate these damages. The physiological responses of a plant to salinity are often complex and multi-faceted, which makes experiments difficult to design and interpret. At basic level, the response of plants to salinity can be described in two main phases: the shoot ion-independent response occurs first, within minutes to days, and is thought to be related to Na+sensing and signaling. Tomato is one the most popular crop in open door and greenhouse cultivation which could face with salinity stresses. Salinity with inducing osmotic stress could have irreversible damages on plant growth and function. Three main salinity tolerance mechanisms have been proposed: on exclusion – the net exclusion of toxic ions from the shoot; tissue tolerance – the compartmentalization of toxic ions into specific tissues, cells and subcellular organelles; and shoot ion-independent tolerance – the maintenance of growth and water uptake independent of the extent of Na+ accumulation in the shoot. In order to face with stresses plant make some internal signals which cause producing different compound and inducing stress resistance. Salicylic acid is one these resistances induced agent. Azealic acid is an organic compound which could increase salicylic acid accumulation in plants.
Materials and Methods: So that, the present experiment was conducted to evaluate the effect of azealic acid and saline irrigation on tomato vegetative and photosynthetic parameters in factorial design based on CRD with three replications. The treatments were salinity level (0, 100, 150 and 200 mM) and azealic acid (0, 8, 10, and 24 mg l-1). The experiment was conducted in pot and in the greenhouse. Gradually in a week salinity treatments applied for plants after that each week once azelaic treatments also applied in each plant. Two weeks later each gas exchange parameters and all parameters needed fresh plant were measured and at the end all parameters with dry matter measured. The photosynthesis traits like transpiration, photosynthesis rate, mesophyll conductance, stomata conductance some stress indices like proline and antioxidant phenol were measured.
Results and Discussion: Results indicated that with increasing salinity level biomass production reduced. It seems that with azealic supplement especially in AZ2 treatment with improving photosynthetic water use efficiency, stomatal and mesophyll conductance has positive effect on photosynthesis. Under low salinity level azealic acid was an effective treatment in photosynthetic parameters although when salinity exceeds more than 100 mM photosynthetic parameters even with azealic acid application reduced. Azealic acid causes a kind of osmotic balance following that the proline content of these treatment reduced. In all salinity levels when azaleic acid applied the phenolic compound increased significantly and the highest was in AZ3. Azaleic acid reduced the Na concentration of leaves it causing the most tolerate reason against salinity when the azaleic acid applied. Although the photosynthetic rate increased with azaleic acid it is not because of chlorophyll content, because the chlorophyll content decreased with azaleic acid. The increase of photosynthesis could be due to decreasing Na concentration of leaves and increasing defense system of plants. Chlorophyll florescence decreased even with azaleic acid in salinity, it means that azaleic acid cannot completely compensate the stress harmful effect. The growth was improved with azaleic acid in salinity; the improvement was greater in root weight compare with shoot weight. Azaleic acid not only prevent decreasing the weight but also improved them in salinity. In defense system of tomato it seems that antioxidant and phenol content were more effective than proline because they are increased with azaleic acid in saline condition effectively compare with proline.
Conclusions: Finally, it seems that until 100mM salinity level azealic acid with maintaining gas exchange capacity in optimum level and inducing osmotic balance could reduce salinity damages. Conclusively, when azaleic acid was applied in 8mg/l that it improved photosynthetic traits like stomata conductance, mesophyll conductance, and photosynthetic water use efficiency compare with control. Azaleic acid can improve the photosynthetic traits when salinity was in low level like 100mM. Proline which is amino acid role as a defense system of plants increased the osmotic adjustment in plant in response to azaleic acid
