Biochemical Responses Of Plants Research Articles

Biochemical responses of Echinochloa polystachya inoculated with a Trichoderma consortium during the removal of a pyrethroid-based pesticide

The biochemical response of plants exposed to pesticides and inoculated with microorganisms is of great importance to explore cleaning up strategies for contaminated sites with pyrethroid-based pesticides. We evaluated the effects of a Trichoderma consortium on the biochemical responses of Echinochloa polystachya plants during the removal of a pyrethroid-based pesticide. Plants were inoculated or not with the Trichoderma consortium and exposed to commercial pesticide H24®, based on pyrethroids. Pesticide application resulted in significant reduction in root protein content (58%), but enhanced content of malondialdehyde (MDA) in shoots, superoxide dismutase (SOD) activity in shoots and roots, and catalase (CAT) activity in roots. Inoculation of Trichoderma consortium in E. polystachya exposed to the pesticide resulted in increased protein content in roots and MDA content in shoots (2-fold). Trichoderma consortium improved protein content and SOD activity (140-fold) in plants. Fungal inoculation increased the removal (97.9%) of the pesticide in comparison to the sole effect of plants (33.9%). Results allow further understanding about the responses of the interaction between plants and root-associated fungi to improving the assisted-phytoremediation of solid matrices contaminated with organic pesticides.

Silicon application enhances wheat defence against Sitobion avenae F. by regulating plant physiological-biochemical responses

Sitobion avenae F. is a highly prevalent and devastating pest in wheat crops, leading to significant yield losses. Silicon (Si) has been widely recognized as an effective inducer of plant resistance against aphids. Nevertheless, the underlying mechanisms governing the physiological and biochemical responses of plants induced by Si defense against S. avenae F. remain incompletely understood. In this study, we conducted experiments by treating wheat leaves with varying concentrations of Tetraethyl orthosilicate (TEOS) spray under aphid infestation. We meticulously observed and recorded the life cycle of S. avenae F. and measured the content of plant hormones, secondary metabolites, and the activity of defense enzymes in wheat leaves. Furthermore, we utilized structural equation modeling to discern the causal correlation between aphid performance and the physiological-biochemical responses of wheat under TEOS sprays. Our findings revealed that a concentration of 3 mmol/L TEOS significantly shortened the net reproductive rate, intrinsic rate and finite rate of increase, and mean generation time of S. avenae F., while simultaneously prolonging the population doubling time. Additionally, the content of lignin, total phenolics, flavonoids, alkaloids, tannin, jasmonic acid (JA), and salicylic acid in wheat leaves exhibited a substantial increase. Furthermore, the activity of phenylalanine ammonia-lyase (PAL), polyphenol oxidase (PPO), catalase, and lipoxygenase in wheat leaves was significantly enhanced. Our results suggest that TEOS spray reduced the survival and population growth of S. avenae F. while enhancing the defense response of wheat against aphids by activating the activity of PAL and PPO in wheat, and increasing the content of total phenolic and JA. This work provides valuable insights for the development of appropriate Si fertilizers for effective pest management and offers robust theoretical support for wheat aphid control through agricultural fertilization strategies.

Mancozeb associated with water deficit: Physiological and biochemical responses of soybean plants

Can oxidative stress from xenobiotics be intensified under water deficit conditions? Based on the hypothesis that the exposure to a xenobiotic aggravates the oxidative damages induced by water deficit, soybean plants were cultivated in pots eqquipped with soil water potential sensors to continuously monitor soil moisture levels. The experiment was conducted in 2020, in a protected environment, using a randomized block design with three replications. To comprehensively evaluate physiological and biochemical responses of plants, we conducted a range of analyses, including measurements of stomatal conductance, leaf temperature, chlorophyll, chlorophyll fluorescence, relative water content, membrane damage, electrical conductivity, lipid peroxidation, concentration of reactive oxygen species – hydrogen peroxide and superoxide, activity of antioxidative enzymes – ascorbate peroxidase, superoxide dismutase, catalase, non-enzymatic compounds – non protein thiols, nitric oxide and proline. Plants that received the application of the fungicide mancozeb showed 1 °C higher temperature compared to the control plants. Irrigated soybean plants had higher nitric oxide content when treated with mancozeb, but under water deficit the higher content was observed in control plants. No deleterious effects of mancozeb as a xenobiotic were observed when applied at the recommended dose for soybean cultivation, even under water deficit conditions. The plants exhibited deleterious effects caused by water deficit, particularly in relation to oxidative stress induced by water shortage. The combination of two stresses (water deficit and xenobiotics) did not result in the maximization of negative effects caused by water stress. By refuting the working hypothesis, it becomes evident that the application of mancozeb to plants under water deficit conditions did not exacerbate the damage induced by this stress. Responses to this combination are contingent upon various factors, including the stress duration, its severity, the plant species involved, and, in the case of xenobiotics, their inherent properties and mode of action within the plant.

Low water availability increases susceptibility to peanut smut (Thecaphora frezzii) in peanut crop

AbstractPeanut smut (causal agent Thecaphora frezzii) and seasonal drought are the two main factors reducing peanut yields in Argentina. There are no previous studies about the effect of drought on peanut smut occurrence. We evaluated the effect of soil water limitation on smut symptoms in greenhouse and field assays. Additionally, we analysed the biochemical responses of plants to the combined stress caused by water limitation and smut infection in greenhouse experiments. We found that a moderate water deficit (30% of soil water‐holding capacity) increased smut symptoms and differentially increased proline and reduced chlorophylls in the host. Subsequently, we studied the correlation between field precipitation data and smut damage from 2015 to 2020 in naturally infected fields with a high T. frezzii spore load in the soils. Strong correlations between precipitation and severely affected pods, severity disease index and incidence were found from January to March (susceptibility window for T. frezzii infections). We suggest a strategy of irrigation in a specific time frame to mitigate smut damage when there is a water deficit in the growing season.

Effect of NPK fertilizer on the biochemical response of tomatoes (Solanum lycopersicum L.)

Increasing nutrient inputs affect plants and soil. Long-term, repeated mineral fertilizer applications may alter the agro-ecosystem. The application of the right amount of fertilizer is primordial to maintaining and improving sustainable plant productivity. The physiological response of the plant provides meaningful information on yield and makes it possible to better choose the doses of fertilization amendments. In order to determine the adequate dose of NPK fertilizer under economically profitable and more environmentally sustainable conditions, we investigated the impact of the chemical fertilizer amended at different NPK fertilizer doses (15, 20, and 25 kg ha-1) on the growth parameters, oxidative metabolism, and yield of Solanum lycopersicum. A complete random block experimental set-up with three doses and four replicates was performed for a greenhouse tomato crop. The results showed that NPK fertilizer influences morphological parameters, and phenolic compounds with the best data correlated to the medium treatment. Likewise, the content of flavonoids, lycopene, and β-carotene in tomato fruits displays a similar trend of variation with all treatment doses. The biochemical responses of plants to mineral fertilizer indicate that a medium dose is suitable, without overuse of fertilizers and pesticides, to reduce the negative impact on the agro-ecosystem.

Morphological and Biochemical Responses of Vigna unguiculata ssp. sesquipedalis in Different Zinc Concentrations

Zinc is an essential trace element required by plants. However, high zinc concentrations can lead to environmental pollution and plant toxicity. This research aimed to investigate how plants respond to different concentrations of zinc (0, 100, 200 and 300 ppm) in soil, using Vigna unguiculata ssp. sesquipedalis (Yard long bean) as a model plant. A total of 12 parameters were collected including plant morphological characteristics such as plant height, leaf number, yield, root length, pod length and fresh weight. Furthermore, key biochemical properties including chlorophyll content, total protein content, total phenolic and flavonoid content in plants were analyzed, in addition to soil pH and electrical conductivity. These parameters were used to determine the morphological and biochemical responses of plants under zinc-stress conditions. The results indicated that different concentrations of zinc significantly decreased the leaf number and pod length V. unguiculata. Soil electrical conductivity was significantly high at 200 ppm zinc. Significant changes in total protein were observed in stems and pods. Moreover, the total phenolic content in leaves showed a significant increase with higher zinc concentrations, while the opposite trend was observed for total phenolic content in V. unguiculata pods. In summary, varying concentrations of zinc had a significant impact on various morphological and biochemical properties of V. unguiculata, exhibiting a distinct pattern specific to each organ. This suggests that V. unguiculata is responsive, adaptive and capable of tolerating abiotic stress induced by a broad range of zinc concentrations.

Specific Streptomyces strain enhances the growth, defensive mechanism, and fruit quality of cucumber by minimizing its fertilizer consumption

BackgroundThe required amounts of chemical fertilizers (NPK) are determined by plant yield, and product quality is given less consideration. The use of PGPRs is an environmentally friendly approach that, in addition to increasing yield, also improves fruit quality. This study examined the role of specific Streptomyces strains in aiding cucumber plants to 1) use fewer NPK fertilizers in the same quantity 2) improve the quality of cucumber fruit, and 3) promote growth and defense system.ResultsIn this study, the effect of 17 Streptomyces strains on the vegetative traits of cucumber seedlings of the Sultan cultivar was evaluated as the first test. Four strains of Streptomyces with the highest root and shoot dry weight were selected from the strains. This experiment was performed to determine the interaction effect of selected strains and different amounts of NPK on cucumber yield, quality, physiological and biochemical responses of plants. The first experiment’s results revealed that strains IC6, Y7, SS12, and SS14 increased significantly in all traits compared to the control, while the other strains dramatically improved several characteristics. Analysis of variance (ANOVA) revealed significant differences between the effect of strains, NPK concentrations, and their interactions on plant traits. The treatments containing 75% NPK + SS12, yielded the most fruit (40% more than the inoculated control). Antioxidant enzymes assay showed that SS12 substantially increased the activity of POX, PPO, and the expression of the genes related to these two enzymes. Hormone assay utilizing HPLC analysis revealed that various strains employ a specific mechanism to improve the immune system of plants.ConclusionsTreatment with strain SS12 led to the production of cucumbers with the highest quality by reducing the amount of nitrate, and soluble sugars and increasing the amount of antioxidants and firmness compared to other treatments. A specific Streptomyces strain could reduce 25% of NPK fertilizer during the vegetative and reproductive growth period. Moreover, this strain protected plants against possible pathogens and adverse environmental factors through the ISR and SAR systems.

Overviewing Drought and Heat Stress Amelioration—From Plant Responses to Microbe-Mediated Mitigation

Microbes (e.g., plant-growth-promoting rhizobacteria, arbuscular mycorrhizal fungi and endophytes) are the natural inhabitants of the soil-plant-environment ecosystem having the potential to ameliorate the negative effects of environmental extremities. Plant-microbe interactions are integral events of agricultural ecosystems which must be studied in order to modulate the systemic mechanisms in field crops. Under changing climatic scenarios, drought and heat stresses tend to induce numerous physiological, morphological, metabolic and biochemical alterations in crop plants, while microbes hold the potential to mitigate these adverse impacts in a sustainable way. However, plant-microbe interaction mechanisms remain understudied owing to their complexities in the rhizosphere and within the cellular systems of plants. In this review, we have attempted to summarize microbes’ interactions with crop plants that tend to influence hormonal and nutrients balance, and the biosynthesis of metabolites and phytohormones, etc. In particular, focus has been kept on the underlying mechanisms related to plant-microbe interactions which confer abiotic stress tolerance. Moreover, various physiological, morphological, metabolic and biochemical responses of plants subjected to water scarcity and elevated temperatures have been synthesized objectively. Lastly, from the perspective of microbes’ application as biofertilizers, both challenges and future research needs to develop microbe-mediated tolerance as a biologically potent strategy have been strategically pointed out.

A meta-analysis on morphological, physiologicaland biochemical responses of plants with PGPR inoculation under drought stress.

Plant growth-promoting rhizobacteria (PGPR) can help plants to resist drought stress. However, the mechanisms of how PGPR inoculation affect plant status under drought remain incompletely understood. We performed a meta-analysis of plant response to PGPR inoculation by compiling data from 57 PGPR-inoculation studies, including 2, 387 paired observations on morphological, physiological and biochemical parameters under drought and well-watered conditions. We compare the PGPR effect on plants performances among different groups of controls and treatments. Our results reveal that PGPR enables plants to restore themselves from drought-stressed to near a well-watered state, and that C4 plants recover better from drought stress than C3 plants. Furthermore, PGPR is more effective underdrought than well-watered conditions in increasing plant biomass, enhancing photosynthesis and inhibiting oxidant damage, and the responses of C4 plants to the PGPR effect was stronger than that of C3 plants under drought conditions. Additionally, PGPR belonging to different taxa and PGPR with different functional traits have varying degrees of drought-resistance effects on plants. These results are important to improve our understanding of the PGPR beneficial effects on enhanced drought-resistance of plants.

Melatonin Pretreatment Alleviated Inhibitory Effects of Drought Stress by Enhancing Anti-Oxidant Activities and Accumulation of Higher Proline and Plant Pigments and Improving Maize Productivity

Drought stress has been shown to have harmful effects on crop productivity worldwide, including in Pakistan, due to rapid climate change scenarios. Extensive work has been reported on the influential role of melatonin (MEL) in either foliar or seed-primed applications; however, its role in root application is seldom reported. We investigated plant biochemical responses, including anti-oxidants, plant pigments, leaf water characteristics, and maize crop production, with MEL treatment under mild and severe drought stress. Maize Cvar. Jalal was subjected to drought stress (60% and 80% of full irrigation) at the four-leaf stage, and MEL was applied as pretreatment with irrigation water at different doses (0, 100, and 200µM). The findings of the study revealed that the Chl a, b, and a + b contents and the carotenoid content significantly increased with MEL application during severe and mild drought stress. After applying 200 µM MEL, leaf water attributes, comprising relative water content (RWC), leaf water content (LWC), and relative saturation deficit (RSD), increased by 1.9%, 100%, and 71.2%, respectively, during mild drought and 17%, 133%, and 32% under severe drought. The anti-oxidant activities of POD, CAT, and APX were remarkably enhanced with MEL during drought stress. Our results showed that root application of 200 µM melatonin boosted seed yield and water productivity by 31% and 38%, and plant biomass increased by 32% and 29% under mild and severe drought stressors compared to plants with no MEL, leading to increased drought tolerance.

Light Spectral Composition Modifies Polyamine Metabolism in Young Wheat Plants.

Although light-emitting diode (LED) technology has extended the research on targeted photomorphogenic, physiological, and biochemical responses in plants, there is not enough direct information about how light affects polyamine metabolism. In this study, the effect of three spectral compositions (referred to by their most typical characteristic: blue, red, and the combination of blue and red [pink] lights) on polyamine metabolism was compared to those obtained under white light conditions at the same light intensity. Although light quality induced pronounced differences in plant morphology, pigment contents, and the expression of polyamine metabolism-related genes, endogenous polyamine levels did not differ substantially. When exogenous polyamines were applied, their roborative effect were detected under all light conditions, but these beneficial changes were correlated with an increase in polyamine content and polyamine metabolism-related gene expression only under blue light. The effect of the polyamines on leaf gene expression under red light was the opposite, with a decreasing tendency. Results suggest that light quality may optimize plant growth through the adjustment of polyamine metabolism at the gene expression level. Polyamine treatments induced different strategies in fine-tuning of polyamine metabolism, which were induced for optimal plant growth and development under different spectral compositions.

Role of phosphorus in Vallisneria natans and biofilm exposure to Pb2+ and Cd2+ stress

Phosphorus (P) could improve the stress resistance and adaptability of submerged macrophytes. This study investigated the physiological and biochemical responses of plants exposed to different P and Pb, Cd concentrations. Alterations of protein synthesis, the DNA methylation (5-mC) level, and the microbial community of biofilm were also evaluated. Results indicated that lower P (0.5 mg·L−1) could promote plant growth and metal enrichment while mitigating the toxicity of metals. Higher P (5.0 mg·L−1) induced a degree of oxidative stress, as confirmed by increased activity of superoxide dismutase, peroxidase, and acid phosphatase, as well as increased malondialdehyde contents. While the variation of metallothionein synthesis and DNA methylation level of the plant was dependent on the level of P and metals in the water. These responses indicated potential mechanisms of P detoxification and intoxication. In addition, more abundant microbial communities were observed in biofilms exposed to P and metals. These findings provide theoretical support for the metal detoxification of P in submerged plants.

Postharvest UV-A radiation affects flavonoid content, composition, and bioactivity of Scutellaria baicalensis root

Ultraviolet A (UV-A) radiation is the main component of solar radiation and can elicit a wide range of biochemical responses in plants. In this study, the effects of UV-A radiation on the flavonoid content, composition, and bioactivity in postharvest Scutellaria baicalensis roots were investigated. The total flavonoid content in S. baicalensis roots under postharvest UV-A radiation increased in a time-dependent manner and reached its maximum value (183.64 g kg−1) on the fifth day. Compared with the control group, the contents of four main flavonoids—baicalin, baicalein, wogonoside, and wogonin increased by 1.68 times, 3.00 times, 2.07 times, and 1.57 times, respectively; and new chemicals including pectolinarigenin, puerarin, isokaempferide, and jaceosidin were detected after 5 d of UV-A radiation. In addition, extracts of S. baicalensis roots exposed to postharvest UV-A radiation showed stronger antioxidant and antibacterial activities than control root extracts. Further correlation analysis revealed that baicalin and baicalein contents in the roots of S. baicalensis after postharvest UV-A radiation were positively correlated with antioxidant activity, while the main flavonoids showed different correlations with various bacteria. These results suggest that the appropriate duration of postharvest UV-A radiation is an effective way to enhance bioactive compound contents and their bioactivities in S. baicalensis roots.

Effect of saccharides on secondary compounds production from stem derived callus of Datura inoxia

Datura inoxia is a subshrub plant known for its toxicity which results from the presence of the tropane alkaloid scopolamine and hyoscyamine. Saccharides are one of the most important elicitors that can alter physiological and biochemical responses in plants. This study targeted to increase the production of secondary metabolites in Datura inoxia avoiding genetic alteration and processes using different nontoxic and biodegradable compounds, utilizing calli induced from Datura inoxia stems to observe the effects of mannitol and sorbitol on the production of the two major secondary metabolites, scopolamine and hyoscyamine. Methanolic extract of the whole plant and callus was used to examine the production of two secondary metabolites in Datura inoxia using HPLC in a qualitative and quantitative manner which revealed the increased production of scopolamine and hyoscyamine in calli. The addition of mannitol and sorbitol in the media had a negative effect on both the fresh and dry weight of the calli but production of scopolamine and hyoscyamine increased significantly. In-vitro anti-microbial assay of hyoscyamine against Escherichia coli ATCC25922 and Candida albicans resulted in total inhibition of both the microbes in concentrations as low as 200 µg/ml.

Important changes in germination, seedling tolerance, and active components content due to drought stress on three licorice (Glycyrrhiza) species

Drought stress triggers complex physiological and biochemical responses in plants. Different plant species have also evolved several morphological, physiological, biochemical, cellular, and molecular mechanisms to overcome drought stress conditions. However, genotype-specific response factors associated with drought tolerance and the balanced relationship between active components and stress conditions are still not fully elucidated. Licorice (Glycyrrhiza Tourn. L.) is a perennial herb of the Leguminosae family which is widely used as a spice in the food industry. It is favored for its sweet and distinctive aromatic flavor, which is attributed to its glycyrrhizic acid, liquiritin, and other components. The influence of drought stress on different species of licorice was analyzed. Seed germination parameters, the activity of anti-oxidative enzymes, osmoregulation, and active compound contents were compared in three licorice species (Glycyrrhiza glabra L., Glycyrrhiza uralensis Fisch., and Glycyrrhiza inflata Bat.). The results indicated a level of drought stress that balanced relatively good growth trends and high expression of active compounds in individual licorice species. With increasing drought stress, G. uralensis and G. glabra had lower values of early germination indicators (germination energy, germination rate, and germination index), when compared to G. inflata. The highest values of antioxidant enzyme activity and active compound content were detected at lower stress levels in both G. uralensis and G. glabra. The active components (glycyrrhizic acid, liquiritin, isoliquiritin, liquiritigenin, isoliquiritigenin, 4′,7-dihydroxyflavone, and licochalcone A) showed significantly different trends in different species under drought stress. The current study will help understand the effects of drought stress on licorice plants. The results highlight the importance of preserving regional genetic diversity for adaptive evolution in response to global climate change. It also provides a theoretical basis for revealing rational cropping regions and formulating adaptive irrigation strategies.

Unravelling Plant Responses to Stress-The Importance of Targeted and Untargeted Metabolomics.

Climate change and an increasing population, present a massive global challenge with respect to environmentally sustainable nutritious food production. Crop yield enhancements, through breeding, are decreasing, whilst agricultural intensification is constrained by emerging, re-emerging, and endemic pests and pathogens, accounting for ~30% of global crop losses, as well as mounting abiotic stress pressures, due to climate change. Metabolomics approaches have previously contributed to our knowledge within the fields of molecular plant pathology and plant–insect interactions. However, these remain incredibly challenging targets, due to the vast diversity in metabolite volatility and polarity, heterogeneous mixtures of pathogen and plant cells, as well as rapid rates of metabolite turn-over. Unravelling the systematic biochemical responses of plants to various individual and combined stresses, involves monitoring signaling compounds, secondary messengers, phytohormones, and defensive and protective chemicals. This demands both targeted and untargeted metabolomics approaches, as well as a range of enzymatic assays, protein assays, and proteomic and transcriptomic technologies. In this review, we focus upon the technical and biological challenges of measuring the metabolome associated with plant stress. We illustrate the challenges, with relevant examples from bacterial and fungal molecular pathologies, plant–insect interactions, and abiotic and combined stress in the environment. We also discuss future prospects from both the perspective of key innovative metabolomic technologies and their deployment in breeding for stress resistance.

Silicon via nutrient solution modulates deficient and sufficient manganese sugar and energy cane antioxidant systems

Manganese (Mn) is highly demanded by Poaceae, and its deficiency induces physiological and biochemical responses in plants. Silicon (Si), which is beneficial to plants under various stress conditions, may also play an important role in plants without stress. However, the physiological and nutritional mechanisms of Si to improve Mn nutrition in sugarcane and energy cane, in addition to mitigating deficiency stress, are still unclear. The objective of this study is to evaluate whether the mechanisms of action of Si are related to the nutrition of Mn by modulating the antioxidant defense system of sugarcane plants and energy cane plants cultivated in nutrient solution, favoring the physiological and growth factors of plants cultivated under Mn deficiency or sufficiency. Two experiments were carried out with pre-sprouted seedlings of Saccharum officinarum L. and Saccharum spontaneum L. grown in the nutrient solution. Treatments were arranged in a 2 × 2 factorial design. Plants were grown under Mn sufficiency (20.5 µmol L−1) and the deficiency (0.1 µmol L−1) associated with the absence and presence of Si (2.0 mmol L−1). Mn deficiency caused oxidative stress by increasing lipid peroxidation and decreasing GPOX activity, contents of phenols, pigments, and photosynthetic efficiency, and led to the growth of both studied species. Si improved the response of both species to Mn supply. The attenuation of the effects of Mn deficiency by Si depends on species, with a higher benefit for Saccharum spontaneum. Its performance is involved in reducing the degradation of cells by reactive oxygen species (21%), increasing the contents of phenols (18%), carotenoids (64%), proteins, modulating SOD activity, and improving photosynthetic and growth responses.

The effect of seed priming at different seed quality by melatonin on seedling emergence and growth characteristic of safflower (Carthamus tinctorius L.) under stress combination of salinity and drought.

IntroductionDrought and salinity are major environmental factors that influence crop productivity worldwide .Plants are normally subjected to a combination of various types of abiotic stresses in nature, such as the combined effects of drought and salinity .Studies have revealed that the physiological and biochemical responses of plants to the interaction of drought and salinity are unique and cannot be directly extrapolated from the responses to the two stresses individually.Storage of orthodox seeds for prolonged period induces their deterioration leading ultimately to loss of their viability. The rate of seed deterioration varies among plant species and seed lots, but high moisture content and high temperature accelerate this process. During long-term storage, all seeds undergo aging processes leading to deterioration in seed quality, especially in the humid tropical regions. However, the rate of seed deterioration can vary among various plant species. When aged seeds are sown, they show decreased viability, lower germinability performance, and produce weak seedlings which could not manage to survive in their habitat. Seed priming (osmoconditioning) has been successfully demonstrated to improve seed germination and seedling establishment for many field crops.The beneficial effects of priming have also been demonstrated on germination and seed emergence, as well as seedling establishment of many crops, particularly under drought and salt stress.Use of chemical compounds as priming agents has been found to improve plant tolerancesignificantly in various crop and non-crop species against a range of different individually applied abiotic stresses.Melatonin, due to its pleiotropic effects can play important roles in improving plant tolerance to adverse conditions.Safflower (Carthamus tinctorius L.) is one of the prospective oilseed crops because it yields about 32–40 % seed oil. However, due to its considerable salt resistance than commonly grown oilseed crops, it is cultivated in arid and semi-arid regions where soil salinity is one of the major threats to agriculture.Drought is very unpredictable among abiotic stresses in terms to occurrence, severity, timing. and duration and safflower can be a promising alternate crop in dryland agro-ecosystems due to its growth potential under water stress without a substantial reduction of oil and seed yields. Safflower cultivation constitutes a more profitable crop for the farmers in some countries, compared to other conventional crops such as barley, lentil, and chickpea.The fact that safflower can overcome environmental stresses such as extreme temperatures, drought, and salinity has facilitated its expansion in areas around the world, where soil and climatic restrictions have impeded the cultivation of conventional food and cash crops.In particular, safflower has demonstrated drought resistance with a slight decrease in crop yield and significant stability in water use efficiency Materials and methods In order to study the effect of seed priming of naturally aged seed by melatonin on seedling emergence and growth characteristic of safflower, three experiments were conducted at seed science technology laboratory, greenhouse and research farm of Aburaihan Campus, the University of Tehran in 2017. The experimental design for all experiment was factorial in completely randomized design (laboratory) and randomized complete block design (research farm and greenhouse) with 4 replicates. The main treatments that common between experiments consist of seed quality (1-naturally aged seed 2- new seed) and seed priming (1-without priming 2- hydropriming 3- Melatonin 0.1 mM 4- Melatonin 0.5 mM). Soil water was determined based on soil moisture release curve, which indicates the relationship between soil water potential andsoil moisture content. Prior to the pot experiments, three samples of wet soil (wet soil = drysoil ? soil moisture content) were dried and soil moisture content at the beginning of experiment was determined.Then pots were equally filled with wet soil. Two pots were considered as references and were weighted each day: one for drought stress and one for other abiotic stresses. The soil moisture content could be obtainable after weighing and it was possible to calculate soil water potential from soil moisture release curve. Results and discussionThe results of this research indicated that the highest percentage of seedling emergence of naturally aged seed obtained by hydropriming and melatonin priming at 0.1 mM by %54.50 and %57.50 that increased the seedling emergence up to %39.74 and %47 respectively, in comparison to control in the farm condition. Also, the results showed that highest percentage of seedling emergence under drought condition belong to melatonin priming at 0.1 mM concentration that increased the seedling emergence up to %154 in comparison to control in the greenhouse condition. The results of this experiment indicated melatonin priming at 0.1 mM concentration led to the highest rate and percentage of seedling emergence under salinity and combination of salinity and drought condition while melatonin priming at 0.5 mM concentration has decreased the rate of seedling emergence.ConclusionsIn general, using of seed priming as a cost-effective method also hydropriming and melatonin priming could enhance the seed quality for growth under salinity and drought conditions.

Biochemical changes induced by phytoplasmas in plants

Abstract Phytoplasmas are cell wall-less and pleomorphic bacterial pathogens that cause considerable yield losses in more than 1000 plant species worldwide and transmitted by sap-feeding insects. Phytoplasma-infected plants exhibit symptoms including witches’ broom, phyllody, virescence, yellowing induced by the phytoplasma effector proteins. It has been revealed that phytoplasmas are capable of modulating biochemical responses of plants involved in defense mechanisms. In this respect, phenolic compounds, free amino acids in source leaves, protein contents, some secondary metabolites, and polyamines were found to increase, while chlorophyll content and photosynthetic activity and the number of chemical compounds were reduced as a consequence of phytoplasma infection. Therefore, the objective of this study was to review the chemical composition changes in phytoplasma-infected plants.

English

Water stress is the most important problem in plant growth and development. Greenhouse trial is carried out on 2 durum wheat (Triticum durum Desf) genotypes (MBB and WAHA), to evaluate the effect of water stress on the biochemical content of leaves, and the possibility of reducing this effect by applying a growth regulator Indole-3-acetic acid (IAA) by seeds soaking and foliar spraying. Water stress causes a large accumulation of proline and soluble sugars and a decrease in the chlorophyll content of the leaves. The results obtained show that the effect of the hormone on the above-mentioned parameters is different according to the genotype and the mode of treatment, as well as the growth phase of the plant, without being able to promote application by soaking or spraying. The application of IAA has relatively reduced the effect of water stress by promoting the synthesis of proline and soluble sugars as osmotic regulators, and by increasing the chlorophyll content of the leaves. proline and soluble sugars concentrations showed negative and significant correlations with those of total chlorophyll. Our present study highlights some biochemical responses of plants to tolerate a water deficit and the possible involvement of exogenus application of IAA, as a phytohormone, in these regulatory mechanisms. Key words: Triticum durum Desf, water stress, Indole-3-acetic acid (IAA), seed soaking, foliar spraying.