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Animal-derived plant biostimulant alleviates drought stress by regulating photosynthesis, osmotic adjustment, and antioxidant systems in tomato plants

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Abstract

Drought stress is one of the major abiotic factors limiting crop growth and yield production. Protein hydrolysates have been used as plant biostimulants in agriculture due to their positive impacts on plant productivity under abiotic stress; however, little is known about their roles in inducing drought tolerance and the underlying mechanisms. Therefore, we investigated the effects of a new pig blood-derived protein hydrolysate (PP) in increasing tomato tolerance to drought stress. We found that foliar PP application reduced the inhibited impacts of drought stress (10% PEG-6000) on tomato growth, as indicated by improved plant growth parameters. Exogenous PP application inhibited the degradation of chlorophyll, maintained chloroplast structures, increased stomatal aperture, and thereby improved photosynthetic rate under drought stress. The higher accumulation of proline, soluble sugars, soluble proteins, inorganic ions including K+, Ca2+, and Mg2+, and subsequently higher relative water content were observed in PP-treated tomato leaves and roots. Moreover, PP application mitigated oxidative damages of drought affected-tomato plants by increasing the activities of superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), and ascorbate peroxidase (APX) and the accumulation of total phenolic, total flavonoid, ascorbic acid, and glutathione. These findings indicated that foliar PP application could obviously alleviate drought stress by regulating stomatal aperture, chloroplast ultrastructure, osmotic alteration, and antioxidant systems. Therefore, protein hydrolysate derived from animal protein is an effective, economical, and environmental plant biostimulant for improving plant performances under drought stress.

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Drought stress considered as a major environmental constraint that frequently limits crop production globally. In the current investigation, drought stress-induced alterations in growth, ion homeostasis, photosynthetic pigments, organic osmolytes, reactive oxygen species (ROS) generation, antioxidative components, and metabolic profile were examined in order to assess the role of silicon (Si) in mitigation of drought effects and to understand the drought adaptive mechanism in two contrasting peanut genotypes (GG7: fast growing and tall, TG26: slow growing and semi-dwarf). Si application significantly improved the leaf chlorophyll content, relative water content % (RWC %), growth and biomass in GG7 compared with TG26 genotype under water stress. Si supplementation considerably promotes the uptake and transport of mineral nutrients under drought condition in both the genotypes, which, eventually promote plant growth. Exogenous application of Si protects the photosynthetic pigments from oxidative damage by reducing membrane lipid peroxidation and either maintained or reduced H2O2 accumulation in both the genotypes. The activity of enzymatic antioxidants like superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX), guaiacol peroxidase (GPX), and glutathione reductase (GR) and non-enzymatic antioxidants like ascorbate (AsA) and glutathione (GSH) were either maintained or increased in both the genotypes in response to Si under drought as compared to those without Si. Silicon-induced higher accumulation of metabolites mainly sugars and sugar alcohols (talose, mannose, fructose, sucrose, cellobiose, trehalose, pinitol, and myo-inositol), amino acids (glutamic acid, serine, histidine, threonine, tyrosine, valine, isoleucine, and leucine) in GG7 genotype as compared to TG26, provides osmo-protection. Moreover, Si application increased phytohormones levels such as indole-3-acetic acid (IAA), gibberellic acid (GA3), jasmonic acid (JA), and zeatin in GG7 genotype under drought stress compared to non-Si treated seedlings suggesting its involvement in signalling pathways for drought adaptation and tolerance. Noteworthy increment in polyphenols (chlorogenic acid, caffeic acid, ellagic acid, rosmarinic acid, quercetin, coumarin, naringenin, and kaempferol) in the Si treated seedlings of GG7 genotype as compared to TG26 under drought stress suggests an efficient mechanism of ROS sequestration in GG7 genotype. Our findings provide comprehensive information on physiological, biochemical, and metabolic dynamics associated with Si-mediated water stress tolerance in peanut. This study indicates that the drought tolerance efficacy of peanut genotypes can be improved by Si application.
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Sodium nitroprusside (SNP) has a decisive function for mitigating water deficit; nevertheless, the specific roles of SNP on chlorophyll biosynthesis, water relation, and osmotic adjustment in marjoram (Origanum marjorana L., Lamiaceae) have not well been established. To assess the function of SNP in alleviating water stress (50% of field capacity), potted marjoram herbs were subjected to watering regimes (well-watered or water-deficit) with or without SNP concentrations (0, 30, 60 μM). Drought caused a significant reduction in water potential (Ψw), osmotic potential (Ψs), turgor potential (Ψp), relative water content (RWC), photosynthetic pigment, chlorophyllide (chlide)a, chlideb, chlorophyll (chl)a/chlidea, chlb/chlideb, and ions, however increased pheophytina (pheoa), protoporphyrin (Proto), Mg-protoporphyrin (Mg-proto), and protochlorophyllide (pchlide). Conversely, osmotic adjustment (OA) was improved, associated with the hyper-accumulation of osmotic adjustment solutes (OAS) leading to an increase in water saturation deficit (WSD), which induced a decrease in dry matter accumulation and shoot fresh weight. Application of SNP decreased Ψw, Ψs, and Ψp and WSD while maintained higher RWC, comparing the plants devoid of SNP supplementation. Supplementary SNP additionally motivated the energetic buildup of various OAO in drought-affected plants that improved OA aptitude, improved water retention capacity, and increased plant growth. Additionally, SNP application increased chlorophyll, carotenoid, pheoa, chlidea, chlideb, chla/chlidea, chlb/chlideb, and decreased Proto, Mg-proto, pchlide, and ions. The findings of the present study clarified that the SNP application improved drought tolerance of marjoram plants, through maintaining ion homeostasis, enhanced OA capacity, increased OAO accumulation, and stabilized chlorophyll biosynthesis.
Article
Drought stress, which causes a decline in quality and quantity of crop yields, has become more accentuated these days due to climatic change. Serious measures need to be taken to increase the tolerance of crop plants to acute drought conditions likely to occur due to global warming. Drought stress causes many physiological and biochemical changes in plants, rendering the maintenance of osmotic adjustment highly crucial. The degree of plant resistance to drought varies with plant species and cultivars, phenological stages of the plant, and the duration of plant exposure to the stress. Osmoregulation in plants under low water potential relies on synthesis and accumulation of osmoprotectants or osmolytes such as soluble proteins, sugars, and sugar alcohols, quaternary ammonium compounds, and amino acids, like proline. This review highlights the role of osmolytes in water‐stressed plants and of enzymes entailed in their metabolism. It will be useful, especially for researchers working on the development of drought‐resistant crops by using the metabolic‐engineering techniques. This article is protected by copyright. All rights reserved.
Article
Drought stress is one of the most adverse abiotic stresses that hinder plants’ growth and productivity, threatening sustainable crop production. It impairs normal growth, disturbs water relations and reduces water-use efficiency in plants. However, plants have evolved many physiological and biochemical responses at the cellular and organism levels, in order to cope with drought stress. Photosynthesis, which is considered one of the most crucial biological processes for survival of plants, is greatly affected by drought stress. A gradual decrease in CO2 assimilation rates, reduced leaf size, stem extension and root proliferation under drought stress, disturbs plant water relations, reducing water-use efficiency, disrupts photosynthetic pigments and reduces the gas exchange affecting the plants adversely. In such conditions, the chloroplast, organelle responsible for photosynthesis, is found to counteract the ill effects of drought stress by its critical involvement as a sensor of changes occurring in the environment, as the first process that drought stress affects is photosynthesis. Beside photosynthesis, chloroplasts carry out primary metabolic functions such as the biosynthesis of starch, amino acids, lipids, and tetrapyroles, and play a central role in the assimilation of nitrogen and sulfur. Because the chloroplasts are central organelles where the photosynthetic reactions take place, modifications in their physiology and protein pools are expected in response to the drought stress-induced variations in leaf gas exchanges and the accumulation of ROS. Higher expression levels of various transcription factors and other proteins including heat shock-related protein, LEA proteins seem to be regulating the heat tolerance mechanisms. However, several aspects of plastid alterations, following a water deficit environment are still poorly characterized. Since plants adapt to various stress tolerance mechanisms to respond to drought stress, understanding mechanisms of drought stress tolerance in plants will lead toward the development of drought tolerance in crop plants. This review throws light on major droughts stress-induced molecular/physiological mechanisms in response to severe and prolonged drought stress and addresses the molecular response of chloroplasts in common vegetable crops. It further highlights research gaps, identifying unexplored domains and suggesting recommendations for future investigations.
Article
Pumpkin seed protein hydrolysate (PH) is a biostimulant product that contains high antioxidant activities, peptides and amino acids. This biostimulant is able to improve plant tolerance to abiotic stresses, including salinity. A pot experiment was conducted during summer season of 2018, with the aim of determining growth and productivity, physio-biochemical attributes, and antioxidant system components in salt (3.9 or 7.8 dS m −1 using NaCl)-stressed Phaseolus vulgaris plants treated with PH (1000 or 2000 μL L-1). Salt stress was applied in irrigation water, and PH was applied three times as foliar application. Under 7.8 dS m −1 , Na + content was significantly increased, however, PH application at 1000 or 2000 μL L-1 reduced it by 11 or 13%, respectively. The negative impacts of salinity on essential nutrients (e.g., N, P, K + , Ca 2+ , and Mg 2+) contents, leaf photo-synthetic pigments contents, and tissue health (in terms of relative water content, membrane stability index, and excised leaf water retention) were considerably mitigated by PH application. Increase in malondialdehyde (MDA) content was associated by increases in proline, soluble sugars, and glutathione contents, and antioxidant enzyme activities under salt stress, however, PH application further improved these parameters along with a worthy reduction in MDA content in salt-stressed plants. PH can maintain plant anatomical features, growth and yield measurements, which were disrupted by salt stress. Results of this study recommend the use of PH as foliar application, especially at 2000 μL L-1 to obtain satisfactory growth and yield of Phaseolus vulgaris plants grown under salt stress up to 7.8 dS m −1 .
Article
The aim of this study was to purify and identify antioxidant peptides from watermelon seed protein hydrolysates (WSPHs-I: Mw<1 kDa) and further evaluate their cytoprotective effects against H2O2-induced oxidative stress in HepG2 cells. After purification by Sephadex G-15 and semi-preparative reversed-phase high performance liquid chromatography (RP-HPLC), five peptides, RDPEER (P1), KELEEK (P2), DAAGRLQE (P3), LDDDGRL (P4), and GFAGDDAPRA (P5) were sequenced by LC-MS/MS and synthesized with solid-phase synthesis method. These peptides showed desirable 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging capacity (IC50: 0.216±0.01∼0.435±0.03), 2,2'-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) radical scavenging capacity (IC50: 0.54±0.02∼1.23±0.03), and oxygen radical absorbance capacity (ORAC) (82.36±1.2∼130.67±2.2 μM TE/mg). Among them, peptide P1 exhibited the strongest antioxidant capacity. Moreover, the results suggested that peptide P1 may protect HepG2 cells from H2O2-induced oxidative damage by significantly inhibiting reactive oxygen species (ROS), [Ca²⁺]i, malondialdehyde (MDA) levels and increasing antioxidative enzyme activities.
Article
The commonly used herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) has an as yet undetermined protective role in mitigating salinity-induced damage in crop plants. The aim of this study was to explore the possible roles of antioxidant defense and methylglyoxal (MG) detoxification systems in enhancing salt tolerance in wheat (Triticum aestivum L. cv. Norin 61) seedlings following pretreatment with 2,4-D. Wheat seedlings were grown hydroponically, pretreated with 10 μM 2,4-D for 48 h, and then exposed to salt stress (150 and 250 mM NaCl) for the next five days. The protective effect of 2,4-D was associated with increased antioxidant enzyme activity and ascorbate and glutathione content, and with decreased malondialdehyde and hydrogen peroxide content and reduced electrolytic leakage. Application of 2,4-D increased glyoxalase enzyme activity, resulting in greater MG detoxification. Seedlings pretreated with 2,4-D showed improved growth, biomass, and leaf water content due to reductions in Na⁺ accumulation and increases in K⁺, Ca²⁺, and Mg²⁺ uptake. Overall, these results highlight the potential use of this common herbicide as a phytoprotectant against salinity stress.
Article
Antioxidants are highly beneficial to human health, and their accumulation in lettuce, one of the most popular leafy vegetables, depends on both genetic and environmental factors. Nitrogen (N) availability plays an essential role in regulating antioxidant accumulation, but the influence of genotype × N interactions on the antioxidant qualities of lettuce is poorly understood. Therefore, the present study investigated the variation of growth and antioxidant qualities of 20 lettuce (Lactuca sativa L.) genotypes (10 green lettuce genotypes and 10 red lettuce genotypes) under limited N (low N, LN) conditions and standard N (high N, HN) conditions. For all 20 genotypes, LN conditions reduced shoot (i.e., leaf) growth, but increased plant concentrations of vitamin C, glutathione, and phenolic compounds, with the exception of carotenoids, compared with HN conditions. Because of reduced biomass under LN conditions, not all lettuce genotypes exhibited increased antioxidant yields or total antioxidant capacity yield. The variation in antioxidant quality was primarily genetically determined. Generally, the green lettuce genotypes exhibited more pronounced increases in antioxidant yields and total antioxidant capacity yield than the red lettuce genotypes under LN conditions. These results suggest that even though LN conditions generally tend to improve the antioxidant qualities of lettuce, the extent of this effect is highly dependent on genotype. Therefore, genotype should be given priority in future studies that aim to improve antioxidant qualities in lettuce through N management.
Article
A probable strategy for increasing the economic sustainability of algal technology would involve the utilization of microalgal biomass as biofertilizer by off-setting the high production costs. The present study focusses on the utilization of mixed algal consortia as biofertilizer for analysing the growth rate of tomato plant. Algal extracts (20-100%) in the form of seed primer and foliar spray were used as biostimulants for the growth of tomato plant. Characterization of algal consortium showed the presence of 40.90% carbohydrates and 26.18% proteins that could potentially act as precursors for bioactive compounds to stimulate plant growth. Faster germination percentage was found with extract concentrations ranging from 20-60% in 3 days compared to the untreated seeds. Seeds treated with cellular extracts of 40% concentration also showed faster plant growth rate after sowing in terms of increase in shoot length 19.86 ± 0.51 cm and root length of 14.87 ± 0.63 cm with a fresh and dry weight of 3.47 ± 0.04 g and 0.389 ± 0.036 g respectively after 20 days. Foliar spraying of 60% algal extracts resulted in total plant height of 7.98 ± 0.19 cm with root length of 5.8 ± 0.16 cm, 46% higher compared to the control. 11 ± 0.35 leaves with chlorophyll content of 13.45 ± 0.307 mg g⁻¹ were also obtained after 20 days, with fresh and dry biomass content of 0.416 ± 0.015 g and 0.062 ± 0.005 g respectively. Thus, microalgal cellular extracts could act as an environmental-friendly and economical alternative to synthetic liquid fertilizer for promoting sustainable agriculture.
Article
Drought alone causes more annual loss in crop yield than all pathogens combined. To adapt to moisture gradients in soil, plants alter their physiology, modify root growth and architecture, and close stomata on their aboveground segments. These tissue-specific responses modify the flux of cellular signals, resulting in early flowering or stunted growth and, often, reduced yield. Physiological and molecular analyses of the model plant Arabidopsis thaliana have identified phytohormone signaling as key for regulating the response to drought or water insufficiency. Here we discuss how engineering hormone signaling in specific cells and cellular domains can facilitate improved plant responses to drought. We explore current knowledge and future questions central to the quest to produce high-yield, drought-resistant crops.
Article
Water scarcity is considered as a key restriction for food production worldwide. Chitosan (Chi) and silicon (Si) play a crucial role in plants metabolic processes under normal or stress conditions. Field experiments were done at the Res. Station, Nat. Res. Cen., El-Nubaria Province, Egypt, in 2014/15 and 2015/16 seasons in a split-plot based on randomized complete block design with three replications, for assessing the defensive role of Chi and/or Si on wheat growth, yield, some physio-anatomical attributes and water use efficiency under different irrigation regimes. The experimental treatments included three irrigation water regimes (100, 70, and 40% of drip irrigation water requirement "IWR") as the main factor, as well as Chi and/or Si (water, 125 mg L⁻¹ Si, 250 mg L⁻¹ Chi, and 125 mg L⁻¹ Si+250 mg L⁻¹ Chi) as the sub-factor. Water deficit significantly decreases plant growth, yield, photosynthetic pigment, and relative water content; whereas significantly induced noticeable changes in leaf and stem anatomy as well as organelle's ultrastructure. Application of Chi + Si gave the highest plant growth and yield attributes, maintaining plant water status, along with improved physiological trials under irrigation regimes. Additionally, the application of Chi + Si under severe drought showed an ameliorative effect on cell ultrastructure compared with drought-affected plants only including well-developed chloroplasts, increased plastoglobules and maintained nucleus and mitochondria structure. Overall, this investigation proposes that the application of 125 mg L⁻¹ Si plus 250 mg L⁻¹ Chi twice at 50 and 70 days from sowing had potential to mitigate the water deficit effects, improving water use efficiency as well as increasing the wheat yield and its quality.
Article
Plant biostimulants (PBS) increase crop productivity inducing beneficial processes in plants. Although PBS can stimulate plant tolerance to some abiotic stresses, their effect in improving crop resistance to herbicide injuries has been barely investigated. Therefore, a study on the effect of a biostimulant (Megafol® - Megafol) on maize (Zea mays L.) tolerance to a chloro-acetanilide herbicide (metolachlor) was carried out. We found that Megafol reduced the negative effects of metolachlor on maize. Indeed, biostimulated samples showed increases in germination, biomass production, vigor index and EC50, with respect to the samples treated with metolachlor alone. Furthermore, plants treated with the herbicide in combination with Megafol showed lower levels of malondialdehyde (MDA). Antioxidant enzymes, namely ascorbate peroxidase (APX), guaiacol peroxidase (GPX) and catalase (CAT), were assayed in samples treated with metolachlor alone or in combination with Megafol, and higher enzymes activities were found in biostimulated plants. The results of this study open the perspective of using Megafol, as well as other suitable plant biostimulants, in improving crop’s capacity to cope with injuries and unwanted effects that herbicide could cause to these species.
Article
Metabolic regulation is one of the main mechanisms involved in the maintenance of cell osmotic potential under abiotic stress. To date, metabolite profiling approaches have been extensively used to characterize the molecular responses to abiotic stress in many plant species. However, studies revealing the specific metabolic responses of plants exposed to water-deficit stress remain limited. Here, we review the most recent developments that advance our understanding of the metabolic response to drought stress in Arabidopsis and rice. We provide an updated schematic overview of the specific metabolic signature of wild-type plants in response to drought.
Article
Plant essential oils represent natural compounds that have a wide range of biologically activities on life systems. Various effects of essential oils on plant growth have been shown; however, their effects on nutrient uptake have not been yet assayed. In this study, effects of two concentrations of rosemary essential oil was evaluated on growth characteristics and nutrient uptake of tomato seedlings in a relatively lime soil and under greenhouse conditions. Treatments were foliar spray of 500 or 1000 ppm oil, soil application of 500 μL oil.kg⁻¹ soil, and a no application control. The seedling growth was changed under essential oil applications particularly by 1000 ppm foliar spray. Foliar application of 1000 ppm essential oil reduced plant height, whereas it increased leaf SPAD value, shoot and root fresh weights, leaf soluble carbohydrates and nutrient concentration of nitrogen, potassium, magnesium, iron and zinc of leaves than control plants. Root fresh weight (but not other traits) was also higher under foliar application of 500 ppm oil or soil application of oil than control plants. The results indicate that rosemary oil has beneficial effects on nutrient uptake of tomato seedlings toward a better growth quality.
Article
Chelates are compounds that are applied to improve nutrition, especially the micronutrients status of plant tissues. During past decades, various chelating agents have been synthesized and introduced to agricultural systems. The recent formulas are aminochelates that are synthesized using various amino acids and a single or several nutrient ions aimed at improving fertilizer use efficiency and more adaptation to environment protection. Apart from their primary use as a micronutrient source, aminochelates represent an effective nitrogen (N) fertilizer in plant nutrition that can avoid negative effects from simple N fertilizers, such as urea. In various studies, higher yield and quality as well as higher concentration of nutrient elements have been obtained by application of aminochelates rather than simple chemical fertilizers. These compounds claimed to be more natural and safer forms of chelating agents, with higher use efficiency and without environmental side effects. However, there is lack of sufficient knowledge especially regarding their detailed impacts and their fate within the soil and plant system. This review provides information concerning the role of aminochelates in plant nutrition and to summarize the previous recent studies that have been done using these fertilizers.
Article
Aluminum (Al) toxicity associated with acid soils represents one of the biggest limitations to crop production worldwide. The root apex of plants is the major perception site of Al toxicity. In Al stressed wheat primary roots, Al accumulation and loss of plasma membrane integrity were highest in the root apex (0-5mm), and decreased along the root axis (5-25mm). To further understand these responses in wheat, spatial profiles of antioxidant responses to Al along the 0-25mm root tip of two wheat genotypes differing in Al tolerance were analyzed. Under Al stress, the lowest root elongation was in the 0-5mm root tip, and more severe inhibition was observed in Al-sensitive genotype than Al-tolerant genotype. The highest increase of Al and hydrogen peroxide (H2O2) was in the 0-5mm zone, with the most pronounced increase of malondialdehyde content and Evans blue uptake after Al exposure, especially in Al-sensitive genotype. The activities of superoxides dismutase (SOD), ascrobate peroxidase (APX), catalase (CAT) and peroxidase (POD) and levels of antioxidants (ascorbic acid, reduced glutathione, dehydroascorbate, glutathione disulfide) were significantly increased along the root tip under Al stress, with the 0-5mm region again being the most active zone. In the same zone, the activities of CAT, APX and contents of antioxidants were higher in Al-tolerant genotype while SOD and POD activities were lower. Our results indicate that Al-induced changes in H2O2 production and antioxidative system in root tip are regulated in a spatially-specific manner, suggesting that this response may play an important role in wheat adaptation to Al toxicity.
Article
Aluminum (Al) toxicity in acid soils is a primary factor limiting plant growth and crop yield worldwide. Considerable genotypic variation in resistance to Al toxicity has been observed in many crop species. In wheat (Triticum aestivum L.), Al phytotoxicity is a complex phenomenon involving multiple physiological mechanisms which are yet to be fully characterized. To elucidate the physiological and molecular basis of Al toxicity in wheat, we performed a detailed analysis of reactive oxygen species (ROS) and reactive nitrogen species (RNS) under Al stress in one Al-tolerant (Jian-864) and one Al-sensitive (Yang-5) genotype. We found Al induced a significant reduction in root growth with the magnitude of reduction always being greater in Yang-5 than in Jian-864. These reductions were accompanied by significant differences in changes in antioxidant enzymes and the nitric oxide (NO) metabolism in these two genotypes. In the Al-sensitive genotype Yang-5, Al induced a significant increase in ROS, NO, peroxynitrite (ONOO-) and activities of NADPH oxidase, peroxidase and S-nitrosoglutathione reductase (GSNOR). A concomitant reduction in glutathione and increase in S-nitrosoglutathione contents was also observed in Yang-5. In contrast, the Al-tolerant genotype Jian-864 showed lower levels of lipid peroxidation, ROS and RNS accumulation, which was likely achieved through the adjustment of its antioxidant defense system to maintain redox state of the cell. These results indicate that Al stress affected redox state and NO metabolism and caused nitro-oxidative stress in wheat. Our findings suggest that these molecules could be useful parameters for evaluating physiological conditions in wheat and other crop species under adverse conditions.
Article
The use of natural plant biostimulants is proposed as a promising and innovative approach to ensure improved and sustainable yields and product quality. A greenhouse experiment was performed to assess the yield performance, leaf net assimilation of CO2, mineral composition of leaves and fruits, and fruit physicochemical quality attributes of two tomato cultivars (Akyra and Sir Elyan) in relation to biostimulant treatments (control or two different concentrations of the legume-derived protein hydrolysate Trainer®). Treated tomato plants were sprayed every 10 days with a solution containing 2.5 and 5.0 ml L-1 of biostimulant. Akyra was found to be richest in K, Ca, Mg, lipophilic and hydrophilic antioxidant activities (LAA and HAA), lycopene, total phenolic and total ascorbic acid. Foliar applications of legume-derived protein hydrolysate at 5.0 ml L-1 increased marketable yield of Akyra and Sir Elyan by modulating yield components differently depending on cultivars: higher number of fruits in Akyra and increase of fruit mean weight in Sir Elyan. Improved yield performance with biostimulant foliar applications at the highest rate was related to improved leaf nutritional status (higher K and Mg) and higher net assimilation of CO2. The application of legume-derived protein hydrolysate at 5.0 ml L-1, and to a lesser degree at 2.5 ml L-1, elicited an increase in antioxidant activities, total soluble solids, mineral composition (K and Mg) as well as bioactive molecules such as lycopene and ascorbic acid, thereby increasing the nutritional and functional quality of the fruits. These findings can assist tomato growers in selecting cultivars and application dose for protein hydrolysate to complement high crop productivity with optimal fruit quality.
Article
Plant-derived protein hydrolysates represent new biostimulant products able to improve crop tolerance to abiotic stresses. The aim of the study was to determine growth, root morphology, SPAD index, chlorophyll fluorescence, leaf mineral composition, and metabolic profiling of greenhouse lettuce either untreated or treated (root or leaf-root application) with a plant-derived protein hydrolysate. For foliar application, plants were sprayed with a solution containing 2.5 ml L −1 of biostimulant, whereas for root application, 100 mL of solution with the same concentration was applied to the growing medium at weekly intervals. Lettuce plants were supplied with two nutrient solutions: non-salt control (1 mM NaCl) or 25 mM NaCl. Salt stress decreased shoot and root dry biomass, SPAD index, chlorophyll fluorescence, leaf mineral composition and increased foliar proline concentration. Root and leaf-root application of the biostimulant increased fresh yield, dry biomass and root dry weight of lettuce under salinity conditions. This was associated with an improvement of plant nitrogen metabolism and an increase of the F v /F m-ratio efficiency in biostimulant-treated plants. Oxidative stress mitigation, increase in osmolytes, changes in sterols and terpenes composition, as well as the less expected increase in glucosinolates were also observed in biostimulant-treated plants grown under saline conditions. The present study proves that the application of plant-derived protein hydrolysate increases plant performance when plants are grown under salinity conditions. The most favorable metabolic profile was obtained when biostimulant was applied to both roots and leaves.
Article
Grapes are an important economic crop and are widely cultivated around the world. Most grapes are grown in arid or semi-arid regions, and droughts take a heavy toll in grape and wine production areas. Developing effective drought-resistant cultivation measures is a priority for viticulture. Melatonin, an indoleamine, mediates many physiological processes in plants. Herein, we examined whether exogenously applied melatonin could improve the resistance of wine grape seedlings grown from cuttings to polyethylene glycol-induced water-deficient stress. The application of 10% polyethylene glycol (PEG) markedly inhibited the growth of cuttings, caused oxidative stress and damage from H2O2 and O2•−, and reduced the potential efficiency of Photosystem II and the amount of chlorophyll. Application of melatonin partially alleviated the oxidative injury to cuttings, slowed the decline in the potential efficiency of Photosystem II, and limited effects on leaf thickness, spongy tissue, and stoma size after application of PEG. Melatonin treatment also helped preserve the internal lamellar system of chloroplasts and alleviated the ultrastructural damage induced by drought stress. This ameliorating effect may be ascribed to the enhanced activity of antioxidant enzymes, increased levels of non-enzymatic antioxidants, and elevated amount of osmoprotectants (free proline). We conclude that the application of melatonin to wine grapes is effective in reducing drought stress.This article is protected by copyright. All rights reserved.
Article
Abscisic acid (ABA) regulates ion channel activity and stomatal movements in response to drought and other stresses. Here, we show that the Arabidopsis thaliana gene NRGA1 is a putative mitochondrial pyruvate carrier which negatively regulates ABA-induced guard cell signaling. NRGA1 transcript was abundant in the A. thaliana leaf and particularly in the guard cells, and its product was directed to the mitochondria. The heterologous co-expression of NRGA1 and AtMPC1 in yeast complemented a loss-of-function MPC mutant. The nrga1 loss-of-function mutant was very sensitive to the presence of ABA in the context of stomatal movements, and exhibited a heightened tolerance to drought stress. Disruption of NRGA1 gene resulted in increased ABA inhibition of inward K(+) currents and ABA activation of slow anion currents in guard cells. The nrga1/NRGA1 functional complementation lines restored the mutant's phenotypes. Furthermore, transgenic lines of constitutively overexpressing NRGA1 showed opposite stomatal responses, reduced drought tolerance and ABA sensitivity of guard cell inward K(+) channel inhibition and anion channel activation. Our findings highlight a putative role for the mitochondrial pyruvate carrier in guard cell ABA signaling in response to drought.
Article
Proline, which increases proportionately faster than other amino acids in plants under water stress, has been suggested as an evaluating parameter for irrigation scheduling and for selecting drought-resistant varieties. The necessity to analyze numerous samples from multiple replications of field grown materials prompted the development of a simple, rapid colorimetric determination of proline. The method detected proline in the 0.1 to 36.0 moles/g range of fresh weight leaf material.
Article
Flavonoid content of mulberry leaves of 19 varieties of species, determined spectrophotometrically in terms of rutin equivalent, varied from 11.7 to 26.6 mg g−1 in spring leaves and 9.84 to 29.6 mg g−1 in autumn leaves. Fresh leaves gave more extract than air-dried or oven-dried ones. HPLC showed that mulberry leaves contain at least four flavonoids, two of which are rutin and quercetin. The percentage superoxide ion scavenged by extracts of mulberry leaves, mulberry tender leaves, mulberry branches and mulberry bark were 46.5, 55.5, 67.5 and 85·5%, respectively, at a concentration of 5 μg ml−1. The scavenging effects of most mulberry extracts were greater than those of rutin (52.0%).