Free Proline Content Research Articles

Heat-Stress-Mitigating Effects of a Protein-Hydrolysate-Based Biostimulant Are Linked to Changes in Protease, DHN, and HSP Gene Expression in Maize

The growth-promoting and heat-mitigating effects of a commercially available protein-hydrolysate-based biostimulant, Kaishi, during the early vegetative stage was investigated by applying it as a foliar spray on soil-grown maize plants or in the nutrient solution of hydroponically grown plants. At 10−3 dilution, the biostimulant inhibited germination and delayed the growth progress, while at 10−6–10−12 dilutions, it promoted shoot and root growth. Heat stress caused biomass reduction, decreased leaf pigment content and the chlorophyll a/chlorophyll b (chl a/b) ratio, caused starch depletion, and increased lipid peroxidation. Kaishi priming resulted in the substantial mitigation of negative stress effects, maintaining growth, stabilizing pigment content and the chl a/b ratio, restoring the leaf starch content, lowering the malondialdehyde (MDA) level, and significantly increasing the free proline content. The expression profiles of a set of genes coding for heat shock proteins (HSPs), dehydrins (DHNs), and proteases were analysed using qRT-PCR after heat stress exposure. The biostimulant-treated plants had higher transcript levels of certain HSPs, DHNs, and protease-coding genes, which remained stable or increased after the applied stress. The results demonstrate that very low concentrations of the biostimulant exerted stress-mitigating effects that could be linked to organ-specific changes in the gene expression of certain stress-inducible proteins.

Comparative transcriptomic analyses of citrus cold-resistant vs. sensitive rootstocks might suggest a relevant role of ABA signaling in triggering cold scion adaption

BackgroundThe citrus genus comprises a number of sensitive tropical and subtropical species to cold stress, which limits global citrus distribution to certain latitudes and causes major economic loss. We used RNA-Seq technology to analyze changes in the transcriptome of Valencia delta seedless orange in response to long-term cold stress grafted on two frequently used citrus rootstocks: Carrizo citrange (CAR), considered one of the most cold-tolerant accessions; C. macrophylla (MAC), a very sensitive one. Our objectives were to identify the genetic mechanism that produce the tolerant or sensitive phenotypes in citrus, as well as to gain insights of the rootstock-scion interactions that induce the cold tolerance or sensitivity in the scion.ResultsPlants were kept at 1 ºC for 30 days. Samples were taken at 0, 15 and 30 days. The metabolomic analysis showed a significant increase in the concentration of free sugars and proline, which was higher for the CAR plants. Hormone quantification in roots showed a substantially increased ABA concentration during cold exposure in the CAR roots, which was not observed in MAC. Different approaches were followed to analyze gene expression. During the stress treatment, the 0-15-day comparison yielded the most DEGs. The functional characterization of DEGs showed enrichment in GO terms and KEGG pathways related to abiotic stress responses previously described in plant cold adaption. The DEGs analysis revealed that several key genes promoting cold adaption were up-regulated in the CAR plants, and those repressing it had higher expression levels in the MAC samples.ConclusionsThe metabolomic and transcriptomic study herein performed indicates that the mechanisms activated in plants shortly after cold exposure remain active in the long term. Both the hormone quantification and differential expression analysis suggest that ABA signaling might play a relevant role in promoting the cold hardiness or sensitiveness of Valencia sweet orange grafted onto Carrizo citrange or Macrophylla rootstocks, respectively. Our work provides new insights into the mechanisms by which rootstocks modulate resistance to abiotic stress in the production variety grafted onto them.

Foliar Application of Spermidine Reduced the Negative Effects of Salt Stress on Oat Seedlings.

The effects of foliar application of spermidine (Spd) on the physiological aspects of salt-stressed oat seedlings were studied under greenhouse conditions. At the seedling stage, the salt-sensitive variety, namely, Caoyou 1 and the salt-tolerant variety, namely, Baiyan 2 were treated with 70 and 100 mM of salt, followed by the foliar application of 0.75 mM Spd or distilled water. Results showed that Spd application increased the activities of superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), and ascorbate peroxidase (APX), and reduced the rate of O2⋅– production and the accumulation of H2O2 and malondialdehyde (MDA). In addition, it increased the level of zeatin riboside (ZR) and the content of endogenous polyamines. The application of Spd increased the contents of soluble sugar, soluble protein, and free proline and helped maintain the osmotic balance of oat leaves. At the same time, foliar Spd treatment helped in maintaining the ion nutrition balance. Specifically, it reduced the content of Na+ and thereby stabilized the ratio of Na+/K+, Na+/Ca2+, and Na+/Mg2+. The effects of Spd application were more obvious for the salt-sensitive cultivar Caoyou 1 and under the lighter 70 mM salt stress.

Integrative Seed and Leaf Treatment with Ascorbic Acid Extends the Planting Period by Improving Tolerance to Late Sowing Influences in Parsley

Abnormal production of reactive oxygen species (ROS) is an undesirable event which occurs in plants due to stress. To meet this event, plants synthesize ROS-neutralizing compounds, including the non-enzymatic oxidant scavenger known as vitamin C: ascorbic acid (AsA). In addition to scavenging ROS, AsA modulates many vital functions in stressed or non-stressed plants. Thus, two-season (2018/2019 and 2019/2020) trials were conducted to study the effect of integrative treatment (seed soaking + foliar spray) using 1.0 or 2.0 mM AsA vs. distilled water (control) on the growth, seed yield, and oil yield of parsley plants under three sowing dates (SDs; November, December, and January, which represent adverse conditions of late sowing) vs. October as the optimal SD (control). The ion balance, osmotic-modifying compounds, and different antioxidants were also studied. The experimental layout was a split plot in a completely randomized block design. Late sowing (December and January) noticeably reduced growth traits, seed and oil yield components, and chlorophyll and nutrient contents. However, soluble sugar, proline, and AsA contents were significantly increased along with the activities of catalase (CAT) and superoxide dismutase (SOD). Under late sowing conditions, the use of AsA significantly increased growth, different yields, essential oil fractions, CAT and SOD activities, and contents of chlorophylls, nutrients, soluble sugars, free proline, and AsA. The interaction treatments of SDs and AsA concentrations indicated that AsA at a concentration of 2 mM was more efficient in conferring greater tolerance to adverse conditions of late sowing in parsley plants. Therefore, this study recommends 2.0 mM AsA for integrative (seed soaking + foliar spraying) treatment to prolong the sowing period of parsley seeds (from October up to December) and avoid damage caused by adverse conditions of late sowing.

Identification of suitable host for sandalwood cultivation in Northern dry zone of Karnataka

Sandalwood (Santalum album L.) is a hemiparasite unable to absorb the required nutrients directly from the soil. Therefore, it needs a suitable host for successful cultivation. The effect of hosts on the growth and development of sandalwood was studied in an eleven-year-old plantation in the Northern dry zone of Karnataka. The sandalwood trees grown with Prosopis (Prosopis juliflora L.) exhibited better growth in terms of tree height (6.58 m), canopy spread (4.64 m), canopy volume (48.60 m3), stem girth (40.70 cm), main stem volume (36.79 dm3) and its annual increment (16.39%). They were also summer hardy and recorded higher chlorophyll, free proline, and soluble sugar in leaves. The summer leafiness of sandalwood was associated with the free proline content in its leaf (r = 0.927), which was in turn correlated with the free proline content in leaves of their respective hosts (r = 0.899). The sandalwood trees with Prosopis also exhibited signs of early heartwood development, thus making Prosopis a suitable host for the commercial cultivation of sandalwood in hot semi-arid conditions.

Capsular polysaccharides and exopolysaccharides from Gloeothece verrucosa under various nitrogen regimes and their potential plant defence stimulation activity

The freshwater and diazotrophic cyanobacterium Gloeothece verrucosa is well-studied for the circadian rhythm of its metabolism but the strain is also known for its production of exopolysaccharides. The impact of the carbon to nitrogen ratio fluctuation on the growth, photosynthetic and nitrogen metabolism and on exopolysaccharide production was investigated. Hence, 4 nitrogen sources at different concentrations were tested: NaNO3, NH4Cl, urea at 1, 2.5 and 17 mM and atmospheric N2 as the sole nitrogen source. The characteristics and composition of the exopolysaccharides were examined. Especially in agriculture, the exopolysaccharides of Gloeothece verrucosa, represented a good alternative to petrochemical derived products due to their non-toxic and biodegradable characteristics. Therefore, the application of the exopolysaccharides as a plant biostimulant is investigated. The results indicated an increase in the growth correlated with an increase in nitrogen concentration, thus a reduction of the carbon to nitrogen ratio. Moreover, the nitrogenase activity of the selected strain is not sufficient for a high biomass production and mimic a nitrogen limiting condition. Exopolysaccharide content follows the inverse tendency with a higher production in the presence of higher carbon to nitrogen ratios. The polymer contains uronic acids, sulphated groups and proteins which reveal an extracellular polysaccharide rich in negative charges. Moreover, the monosaccharide composition is impacted by the nitrogen source. In vitro experimentation on Arabidopsis thaliana and foliar spraying treatment on tomato with various exopolysaccharide solutions indicates that the capsular polysaccharide fraction isolated in this research represents a good candidate for the biostimulation field as it induced an increase in phenylalanine ammonia lyase activity, free proline and anthocyanin content. All these components are known to be implicated in the plant defence mechanisms.

Hydrogen Sulfide Promotes Adventitious Root Development in Cucumber under Salt Stress by Enhancing Antioxidant Ability.

As a gas signal molecule, hydrogen sulfide (H2S) can enhance plant stress resistance. Here, cucumber (Cucumis sativus ‘Xinchun NO. 4’) explants were used to investigate the role of H2S in adventitious root development under salt stress. The results show that sodium chloride (NaCl) at 10 mM produced moderate salt stress. The 100 µM sodium hydrosulfide (NaHS) treatment, a H2S donor, increased root number and root length by 38.37% and 66.75%, respectively, indicating that H2S effectively promoted the occurrence of adventitious roots in cucumber explants under salt stress. The results show that under salt stress, NaHS treatment reduced free proline content and increased the soluble sugar and soluble protein content during rooting. Meanwhile, NaHS treatment enhanced the activities of antioxidant enzymes [peroxidase (POD), superoxide dismutase (SOD), ascorbate peroxidase (APX) and catalase (CAT)], increased the content of ascorbic (ASA) and glutathione (GSH), reduced the content of hydrogen peroxide (H2O2) and the rate of superoxide radical (O2−) production, and decreased relative electrical conductivity (REC) and the content of malondialdehyde (MDA). However, the NaHS scavenger hypotaurine (HT) reversed the above effects of NaHS under salt stress. In summary, H2S promoted adventitious root development under salt stress through regulating osmotic substance content and enhancing antioxidant ability in explants.

The Effects of Salt Stress on Germination, Seedling Growth and Biochemical Responses of Tunisian Squash (Cucurbita maxima Duchesne) Germplasm

Salt stress is considered as one of the most common abiotic stresses reducing the productivity and fruit quality of crop plants. The present study was carried out to assess the salt tolerance among 15 local squash (Cucurbita maxima Duchesne) landraces. Different salt (NaCl) concentrations of 0, 100, 200 and 300 mM were selected in order to evaluate the response of the study germplasm to salt stress based on 12 agronomic parameters and 3 biochemical traits, proline, malondialdehyde (MDA) and chlorophylls. A varied effect of the salt stress level was observed among the studied landraces based on germination potential, as well as on growth and biochemical parameters at seedling stage. Results showed that all landraces were drastically affected at high stress level with a significant variation in their stress response, indicating the existence of considerable genetic variability. Landraces “746” and “747” were the best performing cultivars across stress levels, whereas “1007”, “1008” and “1009” were the most negatively affected. Based on the tested landrace performance, four landraceswere selected and further evaluated at biochemical level, focusing on the determination of compounds that play a key role in the ability to withstand salt stress. The mean MDA content across landraces was generally increased in stressed plants, as compared to the control treatment; the increase was attributed to a peak in MDA content at specific stress levels. In particular, “746” and “1007” showed the maximum content at 100 mM NaCl, while in landrace “751”, MDA content reached its peak at 300 mM NaCl. In addition, the response of most landraces to salt stress involved an increase in free proline content, with the exception of “746”, with the maximum content being observed either at 200 mM (“748” and “751” landraces) or at 300 mM NaCl, where only “747” expressed the highest content. These findings can be extrapolated into efforts to develop more salt-tolerant squash landraces and exhaust the possibilities of using saline water or soils under changing climate conditions.

The transcription factor HcERF4 confers salt and drought tolerance in kenaf (Hibiscus cannabinus L.)

Ethylene response factors (ERF) are members of the APETALA2/ERF transcription factor family, and they play an important role in plant growth, development, and response to various environmental stresses. In this study, an ERF transcription factor HcERF4 was isolated and characterized from kenaf. The results showed HcERF4 contained an open reading frame of 702 bp, which comprised of single AP2 domain. Subcellular localization analysis revealed that the HcERF4 gene was localized in the nucleus and cytoplasm. Transactivation assays in yeast demonstrated that HcERF4 functions as a transcriptional activator. Its expression profile was investigated by real-time PCR analysis in different tissues and under salt as well as drought stress condition. The result revealed that HcERF4 could be markedly induced by salt and drought in a time and concentration dependent manner. Moreover, silencing of HcERF4 by using the VIGS technique, caused a significant growth inhibition under salt or drought stress condition, with lower plant height, stem diameter, and fresh weight, indicating HcERF4 plays key roles response abiotic stress. In addition, physiological index analyses showed that the contents of MDA, O2−, H2O2, and free proline significantly increased, while the activities of antioxidant enzymes were significantly restrained in HcERF4 silenced plants. Furthermore, the expression level of eight important genes involved in plant growth regulation, including HcERF3, HcNAC29, HcSOD, HcP5CS, HcbZIP43, HcWRKY31, HcMYB44, and HcCBP25 were investigated, and the result showed that all eight genes were highly expressed in the leaves of the wild kenaf, but were significantly downregulated in the leaves of the VIGS kenaf plants under drought and salt stress conditions; Consequently, the present results indicate HcERF4 plays a positive role in regulating salt and drought stress in kenaf.

Transcriptomic and proteomic analyses uncover the drought adaption landscape of Phoebe zhennan

BackgroundPhoebe zhennan S.Lee (nanmu) is listed as a threatened tree species in China, whose growth and development, especially during the seedling stage, can be severely limited by drought. Previous studies on nanmu responses to drought stress involved physiological and biochemical analyses, while the molecular mechanisms remained unclear. Therefore, it is of great significance to carry out molecular biology research on the drought resistance of nanmu and reveal the genetic background and molecular regulation mechanism of nanmu drought resistance.ResultsDrought stress enhanced the soluble sugar (SS), free proline(PRO), superoxide anion (O2·−), and hydrogen peroxide (H2O2) contents as well as the peroxidase (POD) and monodehydroascorbate reductase (MDHAR) activities of nanmu. However, glutathione S-transferase (GST) activity was sensitive to drought stress. Further transcriptomic and proteomic analyses revealed the abundant members of the differentially expressed genes(DEGs) and differentially expressed proteins(DEPs) that were related to phenylpropanoid and flavonoid biosynthesis, hormone biosynthesis and signal transduction, chlorophyll metabolism, photosynthesis, and oxidation-reduction reaction, which suggested their involvement in the drought response of nanmu. These enhanced the osmotic regulation, detoxification, and enzyme-induced and non-enzyme-induced antioxidant ability of nanmu. Moreover, 52% (447/867) of proteins that were up-regulated and 34% (307/892) down-regulated ones were attributed to the increase and decrease of transcription abundance. Transcript up (TU) and protein up (PU) groups had 447 overlaps, while transcript down (TD) and protein down (PD) groups had 307 overlaps, accounting for 54% of up and 35% of down-regulated proteins. The lack of overlap between DEGs and DEPs also suggested that post-transcriptional regulation has a critical role in nanmu response to drought.ConclusionsOur research results provide significant insights into the regulatory mechanisms of drought stress in nanmu.

Integrative NPK soil and foliar application improves growth, yield, antioxidant, and nutritional status of Capsicum annuum L. in sandy soils under semi-arid condition

Soils of arid and semi-arid environments are characterized by scant moisture conditions, low clay and organic matter contents, low water holding capacity and low inherent fertility, and hence various management practices including foliar fertilization is essential. The present study aims at assessing the effect of integrated soil and foliar application of nitrogen, phosphorus, and potassium (NPK) fertilizers on growth, yield, and contents of some osmoprotectants, antioxidant, and nutritional status of Capsicum annuum (L.) in sandy soil under semi-arid condition. A pot experiment was conducted with five NPK application treatments: 100% added to the soil + 0% foliar spray, 75% soil + 25% foliar spray, 50% soil + 50% foliar spray, 25% soil + 75% foliar spray, and 0% soil + 100% foliar spray. The results of the study indicate that the integrated treatment of 50% soil + 50% foliar spray proved to be the best treatment compared with other treatments. This treatment significantly increased growth components (leaf area plant‒1, shoot fresh and dry weights) and yield (number of fruits plant‒1, average fruit weight, and fruits weight plant‒1), and the contents of soluble sugars, free proline, and nutrients (NPK); while significantly reduced the contents of ascorbate and glutathione compared to other treatments, including the control. The combined treatment of 75% soil + 25% foliar spray was the second-best treatment with respect to all tested parameters. The study concludes that the recommend integrated treatment of 50% soil + 50% foliar spray minimizes nutrient loss and achieves higher growth and yield of hot pepper plants under semi-arid condition.

The red seaweed Kappaphycus alvarezii antiporter gene (KaNa+/H+) confers abiotic stress tolerance in transgenic tobacco.

Plant establishment, growth, development and productivity are adversely affected by abiotic stresses that are dominant characteristics of environmentally challenged/degraded habitats created in the Anthropocene. Crop breeding for climate resilience properties is need of the hour to sustain the crop productivity. We report on the characterization of Kappaphycus alvarezii (a red seaweed) Na+/H+ antiporter gene (KaNa+/H+) for enhanced salt and osmotic stress tolerance. The KaNa+/H+ antiporter gene was cloned and over-expressed in tobacco under the control of CaMV35S promoter. Transgenic analysis was carried out to assess the stress tolerance ability of tobacco over-expressing KaNa+/H+ antiporter gene. Over-expression of KaNa+/H+ gene improved the seed germination and seed vigor index under stress. Transgenic plants grew better and exhibited delayed leaf senescence. Improved K+/Na+, carotenoid/total chlorophyll and relative water content; lower accumulation of reactive oxygen species (ROS), MDA and Na+; lower electrolyte leakage; better membrane stability index and accumulation of K+, photosynthetic pigment, starch, sugar, free amino acid, proline and polyphenol contents indicated better physiological health of the transgenic tobacco under stress. Transgenic tobacco exhibited higher photosynthesis, photosystem II efficiency, electron transfer rate, photochemical quenching and activity of water splitting complex. Compared with control tobacco, transgenic tobacco exhibited higher expression of stress-defence genes under stress and better recovery after long-term osmotic stress. Lower Na+ cytotoxicity, lower accumulation of ROS and maintenance of the membrane integrity helped transgenic tobacco to maintain the physiological functioning under stress. Present results established K. alvarezii as a potential gene resource and the KaNa+/H+ antiporter gene as a potential candidate gene in molecular breeding of cropsfor development of the degraded land.

Physiological and Molecular Response of Wheat Cultivars to Titanium Dioxide or Zinc Oxide Nanoparticles under Water Stress Conditions

A field trial was conducted through two successive winter seasons 2017/2018 and 2018/2019 to evaluate the influence of TiO2 or ZnO nanoparticles on two wheat cultivars (Gimeza 12 and Sids 13) under different water irrigation requirements of 100% (WW) and 75% (WS). The results showed that drought stress decreases morphological parameters, photosynthetic pigments, and wheat yield (ha−1). However, the total soluble sugars, total free amino acids, proline content, and water productivity were increased. Application of TiO2 or ZnO nanoparticles declines the negative influence of water deficit. Furthermore, SDS-PAGE revealed in Gimeza 12 treated with TiO2 or ZnO nanoparticles, it stimulates the appearance of some proteins at the MW of 28 kDa in WW and WS, while in WS, it records the new polypeptide at 18 kDa. Moreover, Gimeza 12 treated with nano-TiO2 led to the disappearance of two bands at 163 and 51 kDa in WS. However, for Sids13, there was no difference between the treatments in WW and WS except in nano-ZnO at WS that disappeared the polypeptides at MWs of 163, 51, and 18 kDa. Primer SRAP results showed that the plants treated with TiO2 or ZnO nanoparticles had a minor effect at the genomic DNA level, which was illustrated by the appearance or absence of some bands. Besides, the low concentrations of nanoparticles did not damage DNA. On the other hand, one negative marker of −233 bp disappeared in the Gimeza 12 cultivar treated with WS + nano-TiO2 and was revealed in the other treatments using primer SRAP-2. The results showed that the Gimeza 12 cultivar which had the highest grain yield was more tolerant to drought than the Sids 13 cultivar.

Diagnostic significance of the synthesis of phenolic compounds and proline in the leaves of Schisandra chinensis and Actinidia arguta for the indication of the stress levels of plants under conditions of mixed plantings

The peculiarities of the accumulation of polyphenolic compounds and free proline were investigated in the leaves of Actinidia arguta and Shisandra chinensis during their cultivation in vegetation containers with different ratios of the number of plants, namely 1 : 1, 2 : 1, 1 : 2. Monocultural (single-species) planting was used as a control. The content of free proline in plant leaves was carried out according to the method, which is based on the interaction of proline with a ninhydrin reagent, forming a pink-red color. The amount of polyphenolic compounds was determined by the Folin-Ciocalteu method. It was found that the ratio of plants grown together significantly affects the accumulation of primary and secondary metabolites in their leaves. Under conditions of mixed planting, more proline and phenolic substances are accumulated in plant leaves compared to monoculture. The maximum proline content, 19.44 ± 0.91 mg/g of dry weight (DW), was observed in the leaves of A. arguta in the experiment combination with a prevailing number of schisandra plants at a ratio of S. chinensis and A. arguta plants of 2:1. In the same combination, the leaves of actinidia contained the highest amount of phenolic compounds (36.87 ± 2.22 mg/g DW). The studied root exudates of the experimental plants had an allelopathic inhibitory effect on the test culture. The exudates caused 12.0 % average decrease in root growth of A. arguta test objects, and 30.0 % average decrease in root growth of S. chinensis test objects compared with the control. This allows us to conclude about the high activity of schisandra’s allelochemicals, which negatively affect the development of actinidia plants. The optimal ratio of plants A. arguta and S. chinensis when grown together is 2 : 1, since a higher concentration of schisandra plants in a container more stress in actinidia plants, expressed as an increased accumulation of phenols and prolines in its leaves. The result of a comparative analysis of the amount of proline and phenolic compounds can be used to assess the mutual influence of plants in mixed plantings to optimize their growing conditions, which confirms the diagnostic significance of these metabolites for indicating the stress state of the studied plants.

Biochemical Changes on Jute Mallow Plant Irrigated with Wastewater and Its Remediation

Owing to fresh water paucity, farmers are using wastewater for irrigation. This study was performed to assess whether application of Spirulina platensis, Chlorella vulgaris, leaves powder of salix and Ethylenediamine tetraacetic acid could ameliorate the harmful effects of wastewater on Jute mallow. In addition to estimating heavy metals accumulation in Jute mallow leaves (edible part). The results revealed that the contents of total soluble protein in shoot and root throughout the two growth stages, yield parameters and yield components were significantly reduced in wastewater-irrigated plant. The contents of malondialdehyde, free proline, total phenols, superoxide dismutase, catalase, peroxidase and polyphenoloxidase significantly increased in wastewater-irrigated plant than control. Wastewater-irrigated plant has higher levels of Ni, Cd, Pb and Co in leaves, which were beyond recommended limits set by international regulations and the higher rates of plant enrichment was Pb. In contrast, our treatments attenuated the adverse effects of wastewater on metabolic contents, malondialdehyde, non-enzymatic and enzymatic antioxidants, yield parameters and yield components of Jute mallow. Moreover, the concentration of Ni, Cd, Pb and Co in leaves were significantly decreased. Finally, these findings suggested that Spirulina platensis and Chlorella vulgaris treatments could be used for mitigating the harmful effects of wastewater on plants.

Biochemical and physiological changes influenced by drought stress in chickpea (Cicer arietinum L.)

An experiment comprised of eleven different chickpea varieties and five levels of polyethylene glycol (PEG) induced stress treatments for changes in physiological parameters (germination percentage, speed of germination, relative water content, drought tolerance index (DTI) and biochemical parameters (total chlorophyll, free proline content and lipid peroxidation) during in vitro germination. The physiological parameters were decreased under PEG induced drought condition particularly in susceptible variety (GJG-3). Drought stress influences biochemical parameters like free proline and lipid peroxidation. Proline content is increased and lipid peroxidation decreased in drought tolerant varieties compared to susceptible varieties under PEG induced drought. The germination of chickpea varieties was influenced under PEG stress particularly in tolerant varieties and was poorly correlated to osmolytes free proline content. However, based on the result, it can be concluded that the chickpea variety GJG-6 was found to be the most PEG induced drought tolerant and GJG-3 was found to be susceptible among eleven chickpea varieties. The DTI was found to be highly positively correlated with chlorophyll content followed by free proline as biochemical markers and lipid peroxidation was negatively correlated to DTI and free proline content.

Amino acids application alleviated salinity stress in spinach (Spinacia oleracea L.) by improving oxidative defense, osmolyte accumulation, and nutrient balance

Salinity is affecting more than 6 million hectares of cultivated area in Pakistan. The use of amino acids offers a pragmatic solution for minimizing the adverse effects of salinity on Spinacia oleracea L. (spinach). The present study evaluated the possible potential of amino acids in enhancing the salinity tolerance in spinach and identified the probable underlying mechanisms. The experiment comprised of two factors viz. amino acids with total of seven treatments; control, salinity (sal) 100 mM, Methionine + sal, Phenylalanine + sal, Proline + sal, Tyrosine + sal, Combined amino acids + sal, and two spinach cultivars (Desi Palak and VRI-2019). Salinity stress decreased the morpho-physiological attributes of both spinach cultivars, nevertheless, the application of combined amino acids effectively improved the tolerance against salinity stress. Compared with control, all applications of amino acids increased the root and shoot length, fresh and dry weight, number of leaves, and plant yield per plant of both spinach cultivars. However, the maximum was noted by the application of combined amino acids. Combined amino acids triggered the activities of antioxidants (catalase, superoxide dismutase, peroxidase), increased the contents of free proline, phenolics, flavonoids, chlorophyll a, b, carotenoids, calcium, and potassium in root and shoot while decreasing the reactive oxygen species (hydrogen peroxide) and sodium contents in both spinach cultivars under saline conditions. Overall, the VRI-2019 performed better than Desi Palak. The vigorous growth along with higher salinity tolerance because of amino acid treatments was linked to better chlorophyll contents, higher accumulation of osmolytes, maintenance of ionic balance, and an improved antioxidant defense system in Spinacia oleracea.

Effects of High-Temperature Stress on Photosynthetic Characteristics and Antioxidant Enzyme System of Paeonia ostii

Paeonia ostii is an economically important oil crop, which has been widely cultivated in the middle and lower reaches of the Yangtze River in China in recent years. Although P. ostii is highly adaptable to the environment, the prolonged high summer temperature in this region severely inhibits its growth, which adversely affects seed yield and quality. In this study, P. ostii plants were subjected to 20°C/15°C (day/night) and 40°C/35°C (day/night) temperatures for 15 days. The changes in physiological and biochemical indicators of P. ostii under high-temperature stress were initially investigated. The results showed that with the deepening of leaf etiolation, chlorophyll a and chlorophyll b concentration, carotenoid concentration, Soil Plant Analysis Development (SPAD) values and leaf relative water content decreased significantly, while both relative electrical conductivity (REC) and free proline concentration showed an upward trend. Meanwhile, the continuous accumulation of reactive oxygen species (ROS) in P. ostii plants, led to an increased activity of antioxidant enzymes including superoxide dismutase (SOD), peroxidase (POD), catalase (CAT) and ascorbate peroxidase (APX). Moreover, with the extension of the high-temperature treatment, the anatomical structures of P. ostii were destroyed, resulting in a decreased photochemical efficiency of the photosystem II (PSII) reaction center and photosynthesis was inhibited. Taken together, these results provide reference values for understanding the physiological response of P. ostii to high-temperature stress and establish a foundation for further research on the relevant underlying molecular mechanisms.

The Potency of Fungal-Fabricated Selenium Nanoparticles to Improve the Growth Performance of Helianthus annuus L. and Control of Cutworm Agrotis ipsilon

The application of green nanotechnology in agriculture has been receiving substantial attention, especially in the development of new nano-fertilizers and nano-insecticides. Herein, the metabolites secreted by the fungal strain Penicillium chrysogenum are used as a reducing agent for selenium ions to form selenium nanoparticles (Se-NPs). The synthesized Se-NPs were characterized using color change, UV-Vis spectroscopy, Fourier transform infrared (FT-IR) spectroscopy, transmission electron microscopy (TEM), energy dispersive X-ray (EDX), X-ray diffraction (XRD), and dynamic light scattering (DLS). The biomass filtrate of the fungal strain changed from colorless to a ruby red color after mixing with sodium selenite with a maximum surface plasmon resonance at 262 nm. Data exhibits the successful formation of spherical, amorphous Se-NPs with sizes ranging between 3–15 nm and a weight percentage of 38.52%. The efficacy of Se-NPs on the growth performance of sunflower (Helianthus annuus L.) and inhibition of cutworm Agrotis ipsilon was investigated. The field experiment revealed the potentiality of Se-NPs to enhance the growth parameters and carotenoid content in sunflower, especially at 20 ppm. The chlorophylls, carbohydrates, proteins, phenolic compounds, and free proline contents were markedly promoted in response to Se-NPs concentrations. The antioxidant enzymes (peroxidase, catalase, superoxide dismutase, and polyphenol oxidase) were significantly decreased compared with the control. Data analysis showed that the highest mortality for the 1st, 2nd, 3rd, 4th, and 5th instar larvae of Agrotis ipsilon was achieved at 25 ppm with percentages of 89.7 ± 0.3, 78.3 ± 0.3, 72.3 ± 0.6, 63.7 ± 0.3, and 68.7 ± 0.3 respectively after 72 h.

Exogenous application of liquiritin alleviated salt stress and improved growth of Chinese kale plants

Current research was designed to evaluate the role of exogenous liquiritin (750 ppm) in alleviation of salt stress in Chinese kale (Brassica oleracea var. alboglabra). Salt stress (2.5 and 5 dS m−1) caused ionic phytotoxicity through enhancing sodium content and decreasing plant nutrients such as potassium, calcium and magnesium. The 5 dS m−1 salinity treatment significantly declined the root length, shoot length, total chlorophyll, total soluble proteins, leaf relative water content, water use efficiency, total glucosinolates, and ascorbic acid of Chinese kale plants by 39%, 35%, 28%, 15%, 26%, 29%, 35%, and 19% respectively as compared to untreated control. Neverthless, liquiritin supplemented plants showed obvious augmentation in the values of these growth parameters under toxic and non toxic regimes. Similarly, salinized plants showed higher amount of hydrogen peroxide (H2O2), malondialdehyde (MDA), flavonoids, total soluble proteins, proline phenolics and free amino acids in addition to activity of antioxidant enzymes including super oxidase, catalase and peroxidase. Nevertheless, liquiritin alleviated salt induced oxidative stress through decreasing MDA and H2O2 level besides improving antioxidative machinery in treated plants. The salt stress assuagement in liquiritin treated plants was correlated to the elevated biosynthesis of total free amino acids, proline, and total glucosinolate content besides well-organized antioxidant system.