Plant Growth Performance Research Articles

Water Quality and Growth Performance of Nile Tilapia (Oreochromis niloticus), Chia (Salvia hispanica) and Lemon Grass (Cymbopogon citratus) in a Media-based Aquaponics System

High ammonia levels in enclosed fish production systems negatively impact fish growth and hinder optimum production. The objective of this study was to evaluate the (i) biofiltration potential of chia (Salvia hispanica) and lemon grass (Cymbopogon citratus) (ii) the influence of the plant filters on water quality and fish growth in an aquaponic system. Treatments included a control-without plants, S. hispanica, and C. citratus aquaponic systems. The study was conducted for 3 months in Aqualife fish farm, Machakos, Kenya. Water quality parameters, growth performance of fish and plants were monitored during the experiment. The plant treatments significantly (P< 0.05) reduced ammonia levels compared to the control (0.07 ± 0.17 mgL-1). There was a remarkable 32-fold decrease in ammonia compared to the hydroponic inlet. Planted aquaponic systems significantly (P < 0.05) reduced nitrite and nitrate concentrations compared to the control, indicating effective nutrient cycling and improved water quality. Notably, both S. hispanica (115. 5 ± 3.2 g) and C. citratus (130.3 ± 3.32 g) systems significantly (P < 0.05) boosted the growth performance of O. niloticus compared to the control (113. 5 ± 3.2 g). C. citratus performed better (450 ± 9.17 g) than S. hispanica (217.6 ± 2.52 g). These findings highlight the potential of the plants as sustainable and efficient biofilters, enhancing overall aquaponic system performance and contributing to a more productive and environmentally friendly approach to food production.

The Multiple Promoting Effects of Suaeda glauca Root Exudates on the Growth of Alfalfa under NaCl Stress.

Under abiotic stress, plant root exudates can improve plant growth performance. However, studies on the effect of root exudates on the stress resistance of another plant are insufficient. In this study, root exudates (REs) were extracted from Suaeda glauca to explore their effect on alfalfa seedlings under salt stress. The results showed that the plant height and fresh weight of alfalfa significantly increased by 47.72% and 53.39% after 7 days of RE treatment at a 0.4% NaCl concentration. Under 1.2% salt stress, REs reduced the Malondialdehyde content in alfalfa by 30.14% and increased the activity of its antioxidant enzymes (peroxidase and catalase) and the content of its osmotic regulators (soluble sugar and proline) by 60.68%, 52%, 45.67%, and 38.67%, respectively. Soil enzyme activity and the abundance of soil-beneficial bacteria were increased by REs. Spearman analysis showed that urease and neutral phosphatase were related to the richness of beneficial bacteria. Redundancy analysis confirmed that urease affected the composition of the soil bacterial community. The partial least squares structural equation model (PLS-SEM) revealed that REs had a direct positive effect on alfalfa growth under salt stress by regulating the plant's injury and antioxidant systems, and the soil bacterial community had an indirect positive effect on alfalfa growth through soil enzyme activity.

Effect of Light Quality on Seed Potato (Solanum tuberose L.) Tuberization When Aeroponically Grown in a Controlled Greenhouse.

A plant factory equipped with artificial lights is a comparatively new concept when growing seed potatoes (Solanum tuberosum L.) for minituber production. The shortage of disease-free potato seed tubers is a key challenge to producing quality potatoes. Quality seed tuber production all year round in a controlled environment under an artificial light condition was the main purpose of this study. The present study was conducted in a plant factory to investigate the effects of distinct spectrum compositions of LEDs on potato tuberization when grown in an aeroponic system. The study was equipped with eight LED light combinations: L1 = red: blue: green (70 + 25 + 5), L2 = red: blue: green (70 + 20 + 10), L3 = red: blue: green (70 + 15 + 15), L4 = red: blue: green (70 + 10 + 20), L5 = red: blue: far-red (70 + 25 + 5), L6 = red: blue: far-red (70 + 20 + 10), L7 = red: blue: far-red (70 + 15 + 15), L8 = red: blue: far-red (70 + 10 + 20), and L9 = natural light with 300 µmol m-2 s-1 of irradiance, 16/8 h day/night, 65% relative humidity, while natural light was used as the control treatment. According to the findings, treatment L4 recorded a higher tuber number (31/plant), tuber size (>3 g); (9.26 ± 3.01), and GA3 content, along with better plant growth characteristics. Moreover, treatment L4 recorded a significantly increased trend in the stem diameter (11.08 ± 0.25), leaf number (25.32 ± 1.2), leaf width (19 ± 0.81), root length (49 ± 2.1), and stolon length (49.62 ± 2.05) compared to the control (L9). However, the L9 treatment showed the best performance in plant fresh weight (67.16 ± 4.06 g) and plant dry weight (4.46 ± 0.08 g). In addition, photosynthetic pigments (Chl a) (0.096 ± 0.00 mg g-1, 0.093 ± 0.00 mg g-1) were found to be the highest in the L1 and L2 treatments, respectively. However, Chl b and TCL recorded the best results in treatment L4. Finally, with consideration of the plant growth and tuber yield performance, treatment L4 was found to have the best spectral composition to grow quality seed potato tubers.

Water depth-dependent stem elongation of completely submerged Alternanthera philoxeroides is mediated by intra-internodal growth variations.

Complete submergence, especially deep submergence, poses a serious threat to the growth and survival of plants. One study previously showed that Alternanthera philoxeroides (a herbaceous perennial plant) submerged at depth of 2m presented fast stem elongation and reduced stem elongation as water depth increased. In the present study, we aimed to figure out from the morphological and anatomical perspective how the differential growth response of the plant to water depth was achieved. We investigated the elongation of different stem parts and the relationship of stem elongation to cell size and number in A. philoxeroides by conducting experiments using a series of submergence depths (0m, 2m, 5m, and 9m). The results showed that, in comparison with unsubmerged plants, completely submerged plants exhibited enhanced elongation at depths of 2m and 5m but suppressed elongation at depth of 9m in immature stem internodes, and displayed very little elongation in mature stem internodes at any depths. The stem growth of A. philoxeroides at any submergence depth was chiefly caused by the elongation of the basal parts of immature internodes. The elongation of the basal parts of immature internodes was highly correlated to both cell proliferation and cell enlargement, but the elongation of the middle and upper parts of immature internodes correlated nearly only with cell enlargement. This study provided new information on the growth responses of A. philoxeroides to heterogeneous submergence environments and deepened our understanding of the growth performance of terrestrial plants in habitats prone to deep floods.

Growth Performance and Osmolyte Regulation of Drought-Stressed Walnut Plants Are Improved by Mycorrhiza

This study aims to evaluate whether a selected arbuscular mycorrhizal fungus, Diversispora spurca, improves growth in drought-stressed walnut (Juglans regia L. cv. Qingxiang) plants and whether this improvement is associated with changes in osmolyte (fructose, glucose, sucrose, soluble protein, proline, and betaine) levels. After 60 days of soil drought treatment (50% of maximum field water-holding capacity), root D. spurca colonization rate and soil mycelium length decreased by 13.57% and 64.03%, respectively. Soil drought also inhibited the growth performance of aboveground (stem diameter, leaf number, leaf biomass, and stem biomass) and underground (root projected area, surface area, and average diameter) parts, with uninoculated plants showing a stronger inhibition than D. spurca-inoculated plants. D. spurca significantly increased these growth variables, along with aboveground part variables and root areas being more prominent under drought stress versus non-stress conditions. Although drought treatment suppressed the chlorophyll index and nitrogen balance index in leaves, mycorrhizal inoculation significantly increased these indices. Walnut plants were able to actively increase leaf fructose, glucose, sucrose, betaine, and proline levels under such drought stress. Inoculation of D. spurca also significantly increased leaf fructose, glucose, sucrose, betaine, proline, and soluble protein levels under drought stress and non-stress, with the increasing trend in betaine and soluble protein being higher under drought stress versus non-stress. Drought stress dramatically raised leaf hydrogen peroxide (H2O2) levels in both inoculated and uninoculated plants, while mycorrhizal plants presented significantly lower H2O2 levels, with the decreasing trend higher under drought stress versus non-stress. In conclusion, D. spurca symbiosis can increase the growth of drought-stressed walnut plants, associated with increased osmolyte levels and decreased H2O2 levels.

Enhanced Seedling Growth and Physiological Performances of Melia azedarach L. by Foliar Application of 24-Epibrassinolide under Salt Stress

Salinity is a serious environmental problem following a worsening trend. This study investigates the role of 24-epibrassinolide(EBR) in regulating plant growth and physiological performances, particularly in alleviating the negative effects of salt stress. Melia azedarach L. seedlings from two seed sources, Sheyang (SY) and Xiashu (XS), were exposed to sea salt and treated with different concentrations of EBR within a 60-day period. The results demonstrate that appropriate EBR application improved the seedlings’ stress tolerance by promoting growth and physiological systems. In terms of the relative increment, it showed that a difference of 1.45% and 1.13% in the SY and XS groups was the positive effect of the highest EBR treatment concentration. As for diameter growth, the difference observed was 2.51% and 1.80% for the SY and XS groups, respectively. In all physiological measurements, including the content of photosynthetic pigments, water relations, membrane stability, osmolytes and antioxidant enzymes, significant changes generally observed between salt stress alone and the highest EBR treatment concentration. A better performance was observed in the SY seed source, which is of a coastal nature. These findings contribute to our understanding of Melia azedarach’s adaptation to changing environments and provide potential for further molecular studies as well as valuable insights for forestry, agricultural and ecological research.

Synthesis and Characterization of Chitosan Encapsulated Zinc Oxide Nanoparticles and its Application in Maize under Zinc Deficit Soil

Zinc deficiency is a growing concern among the global population, and it can be attributed to the depletion of significant portions of agricultural land and the production of foods that are low in zinc. In the current study, an efficiency-centric method of maize cultivation with zinc oxide nanoparticles encapsulated in chitosan (Cs-ZnO NPs) is proposed and evaluated. In order to investigate, NPs were chemically synthesized using process improvement for better size and shape and characterized using Scanning electron microscope (SEM), Energy-dispersive X-ray spectroscopy (EDS) and Transmission electron microscope (TEM). The NPs under characterization showed less than 100 nm diametric globular particles. A field experiment was conducted in randomized block design with six different treatments to study the impact of foliar applied Zn at various concentrations (50, 100, and 150 mg L-1) through Cs-ZnO NPs on plant growth, SPAD and grain yield in maize plant, with respect to foliar ZnSO4 @0.5 %, chitosan @150 mg L-1 and the control. The highest grain yield of 52.5 q ha-1 in maize was recorded with Zn supplied through Cs-ZnO NPs at 100 mg L-1, compare to other treatments. Similarly significant improvements in plant height and chlorophyll content were noted at 100 mg L-1 Zn through Cs-ZnO NPs. These results indicates that Cs-ZnO NPs can improve grain yield and plant growth performance of maize in a sustainable and efficiency centric manner.

Seed priming with corona discharge plasma modified growth performance, improved metabolism, and elicited production of tropane alkaloids in Datura inoxia seedlings; plasma technology for application in plant in‐vitro cultures

AbstractThis study monitored the growth, biochemical, and developmental responses of Datura seedlings to the cold plasma. The effectiveness of different methods was explored to break seed dormancy. Germinating seeds were exposed to corona discharge plasma for different durations, including 0, 60, 120, 180, and 300 s. A procedure consisting of illumination with a red light (20 min), soaking in water (4°C for 48 h), and removing a part of Testa was the best method for breaking seed dormancy. The plasma treatments of 60, 120, and 180 s improved the plant growth performance, while this trait was declined in response to the plasma treatment of 300 s. The proline concentrations in both root and leaves displayed a linear significant upward trend in response to the plasma treatments. The plasma for 180 s was the most effective method to increase tropane alkaloids. With increasing the exposure time from 60 to 300 s, the leaf soluble phenols were linearly enhanced. The plasma application for 60, 120, and 180 s significantly augmented total protein concentration, while the exposure of seeds for 300 s significantly diminished it. The highest amounts of photosynthetic pigments (chlorophylls and carotenoids) were recorded in the seedlings treated with plasma for 120 and 180 s. The activities of enzymatic antioxidants (catalase and peroxidase) showed a similar upward trend to that of proline. The plasma priming also improved the phenylalanine ammonia‐lyase activity (a secondary metabolism index). Further investigations are needed to optimize plasma parameters and understand the involved mechanisms to maximize its benefits while minimizing potential risks.

Bacterially enhanced plant-growing media for controlled environment agriculture.

Microbe-plant interactions in the root zone not only shape crop performance in soil but also in hydroponic cultivation systems. The biological and physicochemical properties of the plant-growing medium determine the root-associated microbial community and influence bacterial inoculation effectiveness, which affects plant growth. This study investigated the combined impact of plant-growing media composition and bacterial community inoculation on the root-associated bacterial community of hydroponically grown lettuce (Lactuca sativa L.). Ten plant-growing media were composed of varying raw materials, including black peat, white peat, coir pith, wood fibre, composted bark, green waste compost, perlite and sand. In addition, five different bacterial community inocula (BCI S1-5) were collected from the roots of lettuce obtained at different farms. After inoculation and cultivation inside a vertical farm, lettuce root-associated bacterial community structures, diversity and compositions were determined by evaluating 16S rRNA gene sequences. The study revealed distinct bacterial community structures among experimental replicates, highlighting the influence of raw material variations on root-associated bacterial communities, even at the batch level. However, bacterial community inoculation allowed modulation of the root-associated bacterial communities independently from the plant-growing medium composition. Bacterial diversity was identified as a key determinant of plant growth performance with green waste compost introducing Bacilli and Actinobacteria, and bacterial community inoculum S3 introducing Pseudomonas, which positively correlated with plant growth. These findings challenge the prevailing notion of hydroponic cultivation systems as sterile environments and highlight the significance of proper plant-growing media raw material selection and bacterial community inoculation in shaping root-associated microbiomes that provide stability through microbial diversity. This study supports the concept of creating bacterially enhanced plant-growing media to promote plant growth in controlled environment agriculture.

Alleviation of lead stress in sunflower (Helianthus annuus L.) by growth-promoting rhizobacterium and neem cake

ABSTRACT Lead causes toxicity and affects plant growth by disturbing photosynthesis and the functions of enzymes. Its removal from the soil is a challenging issue. The present study investigates the efficacy of neem cake as soil organic amendment and inoculation of a lead-tolerant plant growth-promoting rhizobacterium (PGPR), Pseudomonas aeruginosa, to decrease the effects of lead toxicity in sunflower, when cultivated with and without neem cake amended soil. The experiment was performed in earthen pots (10 cm diam) containing 1 kg sandy loam soil irrigated with 0.2 and 0.5 mM lead. P. aeruginosa used in this experiment has a lead remediation capacity of 99% when subjected to 0.6 mM lead. The combination of organic amendment with PGPR improved the growth and physiological performance of the stressed sunflower plant. The plants treated with PGPR in amended soil showed healthier roots and shoots and demonstrated better scavenging of free radicals, with improved H2O2 scavenging and peroxidase (POD) activities. Neem cake and P. aeruginosa separately and combined significantly enhanced sugar contents and POD activity while lowering stress-induced higher levels of phenols and ascorbic acid. The combined application of neem cake and P. aeruginosa could be a promising solution for growing sunflower plants in lead-contaminated soil.

Evaluating Impacts of Biosynthetic Silver Nanoparticles on Morphophysiological Responses in Barley (Hordeum vulgare L.)

In recent years, nanotechnology has shown promising potential to enhance sustainable agriculture. Besides their use as antifungal and antimicrobial agents, silver nanoparticles (AgNPs) are the most widespread nanomaterials and are found in a capacious range of agrocommercial products. This study was designed to investigate the responses of morphophysiological characteristics in barley (Hordeum vulgare L.) to biologically synthesized silver nanoparticles. Spherical shapes with 8–20 nm size AgNPs at different concentrations (0, 50, 100, 150, 200, and 250 mg/L) were applied to barley plants in a hydroponic system. Following 7 days of sowing, the growth performance, chlorophyll contents, oxidative damage, and the activity level of antioxidant enzymes were quantified in different parts of the plant. The results indicated a remarkable boost in the growth performance and chlorophyll contents of barley plants up to a concentration of 150 mg/L. Interestingly, the levels of proline, lipid peroxidation, enzymes; superoxide dismutase (SOD), catalase (CAT), (APX), and (GR) activities were enhanced significantly in response to all AgNPs treatments. In general, the application of AgNPs substantially improved the growth and related morphophysiological attributes in barley. Our results provide new insights with respect to the effects of AgNPs on barley growth and their potential applications in increasing the performance of other crop species.

Effect of Intra Row Spacing on Growth, Yield Components and Yield of Garlic (Allium Sativum L) at Fitch, North Showa Zone of Oromia, Ethiopia

Garlic (Allium sativum L.) is a monocotyledonous aromatic plant belonging to the Alliaceae family and genus Allium. It is used as a spice and medicinal plant. The production of garlic in Ethiopia is low as compared to other growing countries. This is due to different factors like the unavailability of appropriate disease-free seeds (Cloves), inappropriate agronomic practices, i.e., sowing time, seed rate, and both intra- and inter-row spacing. That is the reason why the research report was studied. A field experiment was conducted at the Fiche, Salale University, General Tadesse Biru campus demonstration site during the 2020 cropping season. The objective of the study was to identify the effect of intra-row spacing on the growth, yield, and yield components of garlic. One local variety of garlic, which was bought from Fiche Market, was used for the field experiment. The experiment was laid out using a randomized complete block design (RCBD) with three replications and four treatments/intrarow spacing, i.e., 8cm, 10cm, 12 cm, and 14cm between plants. Growth, yield, and yield components data were collected and subjected to analysis of variance (ANOVA) using SAS 9.3, and least significant difference (LSD) at p<0.05 probability was used to separate means. The ANOVA showed significant variation among all collected parameters. The wider the plant spaced, the better the growth performance of the garlic plant. However, the yield-related parameters are good indicators of yield. Thus, treatments, which are bulb weight and number of cloves per bulb, showed better performance of morphological parameters and also suggest a positive relationship with increasing plant spacing statistically. According to those ANOVA results, farmers or growers may produce more yield with a plant spacing of 14*25 because all parameters are significant as compared to other treatments.

Negotiating soil water deficit in mycorrhizal trifoliate orange plants: A gibberellin pathway

Gibberellins (GAs), an important endogenous hormone, serve a crucial regulatory role in plants’ resistance to environmental stress, whereas it is unclear whether and how arbuscular mycorrhizal fungi (AMF) regulate the profile of GAs in plants exposed to soil water deficit (SWD). This study aimed to analyze how Rhizoglomus intraradices inoculation affected plant growth performance, antioxidant enzyme activities, and the composition, synthesis, metabolism, and signaling pathways of GAs in the roots of trifoliate orange (Poncirus trifoliata) under a 10-week SWD. Although the SWD decreased both root AMF colonization and soil hyphal length, mycorrhizal plants nevertheless outperformed non-mycorrhizal plants in terms of growth performance, as well as peroxidase (70.0%) and catalase (149.2%) activities, indicating greater drought tolerance. A total of nine GAs compositions were detected in the roots, with bioactive GA4 exclusively found in AMF roots. AMF colonization significantly reduced bioactive GA3 levels by 37.9%, while it increased inactive GA8, GA9, and GA15 levels under SWD by 522.2%, 100.0%, and 2500.0%. Inoculation with AMF also up-regulated the expression of PtCPS, PtPKS, and PtKO in GA synthesis pathways of roots and the expression of PtGA20ox, PtGA3ox, and PtGA2ox in GA metabolisms under SWD. In addition, the expression of DELLA genes PtGaipb and PtGai associated with GA signaling pathways was further up-regulated under SWD by AMF inoculation. It is concluded that AMF regulated the composition, synthesis, and deactivation of GAs in roots to promote plant growth, along with an increase in PtGaipb and PtGai expression to possibly initiate mycorrhizal signaling pathways in response to SWD.

Fostering plant growth performance under drought stress using rhizospheric microbes, their gene editing, and biochar.

Stress due to drought lowers crop yield and frequently leads to a rise in food scarcity. Plants' intricate metabolic systems enable them to tolerate drought stress, but they are unable to handle it well. Adding some external, environmentally friendly supplements can boost plant growth and productivity when it comes to drought-stressed plants. In order to prevent the detrimental effects of drought in agricultural regions, environmentally friendly practices must be upheld. Plant growth-promoting rhizobacteria (PGPR) can exhibit beneficial phytostimulation, mineralization, and biocontrol activities under drought stress. The significant impact of the PGPR previously reported has not been accepted as an effective treatment to lessen drought stress. Recent studies have successfully shown that manipulating microbes can be a better option to reduce the severity of drought in plants. In this review, we demonstrate how modifying agents such as biochar, PGPR consortia, PGPR, and mycorrhizal fungi can help overcome drought stress responses in crop plants. This article also discusses CRISPR/Cas9-modifiable genes, increase plant's effectiveness in drought conditions, and increase plant resistance to drought stress. With an eco-friendly approach in mind, there is a need for practical management techniques having potential prospects based on an integrated strategy mediated by CRISPR-Cas9 editing, PGPR, which may alleviate the effects of drought stress in crops and aid in achieving the United Nation Sustainable Development Goals (UN-SDGs-2030).

HvGSK1.1 Controls Salt Tolerance and Yield through the Brassinosteroid Signaling Pathway in Barley.

Brassinosteroids (BRs) are a class of plant steroid hormones that are essential for plant growth and development. BRs control important agronomic traits and responses to abiotic stresses. Through the signaling pathway, BRs control the expression of thousands of genes, resulting in a variety of biological responses. The key effectors of the BR pathway are two transcription factors (TFs): BRASSINAZOLE RESISTANT 1 (BZR1) and BRI1-EMSSUPPRESSOR 1 (BES1). Both TFs are phosphorylated and inactivated by the Glycogen synthase kinase 3 BRASSINOSTEROID INSENSITIVE2 (BIN2), which acts as a negative regulator of the BR pathway. In our study, we describe the functional characteristics of HvGSK1.1, which is one of the GSK3/SHAGGY-like orthologs in barley. We generated mutant lines of HvGSK1.1 using CRISPR/Cas9 genome editing technology. Next Generation Sequencing (NGS) of the edited region of the HvGSK1.1 showed a wide variety of mutations. Most of the changes (frameshift, premature stop codon, and translation termination) resulted in the knock-out of the target gene. The molecular and phenotypic characteristics of the mutant lines showed that the knock-out mutation of HvGSK1.1 improved plant growth performance under salt stress conditions and increased the thousand kernel weight of the plants grown under normal conditions. The inactivation of HvGSK1.1 enhanced BR-dependent signaling, as indicated by the results of the leaf inclination assay in the edited lines. The plant traits under investigation are consistent with those known to be regulated by BRs. These results, together with studies of other GSK3 gene members in other plant species, suggest that targeted editing of these genes may be useful in creating plants with improved agricultural traits.

Timing of systemic resistance induced by local exogenous ABA application within clonal network of stoloniferous herb Centella asiatica subjected to low water availability.

Resistance traits of plants can be activated both at the damaged site and undamaged parts. Systemic resistance induced by local exogenous abscisic acid (ABA) application alleviated negative effect of low water availability on growth performance of clonal plant. However, timing of systemic resistance was poorly understood. Timing of systemic resistance refers to its activation and decay time within clonal network. Clonal fragment of Centella asiatica with four successive ramets (including first-oldest, second-older, third-old and fourth-young ramets) subjected to low water availability (20% soil moisture content) was used to explore effects of local exogenous ABA application on the timing of resistance activation and decay. Systemic resistance activated by local exogenous ABA application after 4 days remained at least 28 days. Compared with control, biomass accumulation of whole clonal fragment, root biomass and ratio of belowground to aboveground biomass significantly increased by local exogenous ABA application after 28 days. It is suggested that rapid activation and delay of resistance response induced by local exogenous ABA application within clonal network may improve fitness of clonal plant subjected to abiotic stress.

Elevated tropospheric ozone and crop production: potential negative effects and plant defense mechanisms.

Ozone (O3) levels on Earth are increasing because of anthropogenic activities and natural processes. Ozone enters plants through the leaves, leading to the overgeneration of reactive oxygen species (ROS) in the mesophyll and guard cell walls. ROS can damage chloroplast ultrastructure and block photosynthetic electron transport. Ozone can lead to stomatal closure and alter stomatal conductance, thereby hindering carbon dioxide (CO2) fixation. Ozone-induced leaf chlorosis is common. All of these factors lead to a reduction in photosynthesis under O3 stress. Long-term exposure to high concentrations of O3 disrupts plant physiological processes, including water and nutrient uptake, respiration, and translocation of assimilates and metabolites. As a result, plant growth and reproductive performance are negatively affected. Thus, reduction in crop yield and deterioration of crop quality are the greatest effects of O3 stress on plants. Increased rates of hydrogen peroxide accumulation, lipid peroxidation, and ion leakage are the common indicators of oxidative damage in plants exposed to O3 stress. Ozone disrupts the antioxidant defense system of plants by disturbing enzymatic activity and non-enzymatic antioxidant content. Improving photosynthetic pathways, various physiological processes, antioxidant defense, and phytohormone regulation, which can be achieved through various approaches, have been reported as vital strategies for improving O3 stress tolerance in plants. In plants, O3 stress can be mitigated in several ways. However, improvements in crop management practices, CO2 fertilization, using chemical elicitors, nutrient management, and the selection of tolerant crop varieties have been documented to mitigate O3 stress in different plant species. In this review, the responses of O3-exposed plants are summarized, and different mitigation strategies to decrease O3 stress-induced damage and crop losses are discussed. Further research should be conducted to determine methods to mitigate crop loss, enhance plant antioxidant defenses, modify physiological characteristics, and apply protectants.

Effect of biofertilizer containing Thiobacillus bacteria along with different levels of chemical sulfur fertilizer on growth response and photochemical efficiency of small radish plants (Raphanus sativus L. var. shushtari) under greenhouse conditions

Biofertilizers containing sulfur-oxidizing bacteria increase the accessibility of roots to nutrients by reducing soil pH. These biofertilizers can significantly contribute to soil fertility and increase plant growth. The present study was conducted to investigate the effect of a mixture of sulfur biofertilizer (SB) and granular sulfur fertilizer (GSF) on the growth, absorption of some elements, and photochemical efficiency of PSII in small Raphanus sativus grown in greenhouse conditions. GSF, including 0, 200, 400, and 600 kg ha−1 was added to the soil of the pots without or with biofertilizer containing Thiobacillus bacteria. The results showed that applying biofertilizer along with different levels of GSF increased the fresh weight and contents of anthocyanins, soluble sugars, starch, and some nutrients in leaves and swollen red roots. In addition, these treatments led to an increase in shoot length and photosynthetic pigments. In plants treated with a mixture of biofertilizer and chemical fertilizer, the photochemical efficiency of photosynthesis improved. The results of this study suggest the use of SB along with GSF (even at low and medium levels) can improve the growth and photosynthetic performance of radish plants in most of the measured indicators, at least in current experimental conditions. The results of this study can be significant for less use of chemical fertilizers and the production of agricultural products with higher food security, especially in developing countries.

Strigolactone GR24-mediated mitigation of phosphorus deficiency through mycorrhization in aerobic rice

Strigolactones (SLs) are a new class of plant hormones that play a significant role in regulating various aspects of plant growth promotion, stress tolerance and influence the rhizospheric microbiome. GR24 is a synthetic SL analog used in scientific research to understand the effects of SL on plants and to act as a plant growth promoter. This study aimed to conduct hormonal seed priming at different concentrations of GR24 (0.1, 0.5, 1.0, 5.0 and 10.0 µM with and without arbuscular mycorrhizal fungi (AMF) inoculation in selected aerobic rice varieties (CR Dhan 201, CR Dhan 204, CR Dhan 205, and CR Dhan 207), Kasalath-IC459373 (P-tolerant check), and IR-36 (P-susceptible check) under phosphorus (P)-deficient conditions to understand the enhancement of growth and priming effects in mycorrhization. Our findings showed that seed priming with 5.0 µM SL GR24 enhanced the performance of mycorrhization in CR Dhan 205 (88.91 %), followed by CR Dhan 204 and 207, and AMF sporulation in CR Dhan 201 (31.98 spores / 10 gm soil) and CR Dhan 207 (30.29 spores / 10 g soil), as well as rice growth. The study showed that the highly responsive variety CR Dhan 207 followed by CR Dhan 204, 205, 201, and Kasalath IC459373 showed higher P uptake than the control, and AMF treated with 5.0 µM SL GR24 varieties CR Dhan 205 followed by CR Dhan 207 and 204 showed the best performance in plant growth, chlorophyll content, and soil functional properties, such as acid and alkaline phosphatase activity, soil microbial biomass carbon (MBC), dehydrogenase activity (DHA), and fluorescein diacetate activity (FDA). Overall, AMF intervention with SL GR24 significantly increased plant growth, soil enzyme activity, and uptake of P compared to the control. Under P-deficient conditions, seed priming with 5.0 µM strigolactone GR24 and AMF inoculum significantly increased selected aerobic rice growth, P uptake, and soil enzyme activities. Application of SLs formulations with AMF inoculum in selected aerobic rice varieties, CR Dhan 207, CR Dhan 204, and CR Dhan 205, will play an important role in mycorrhization, growth, and enhancement of P utilization under P- nutrient deficient conditions.

Relative effects of melatonin and hydrogen sulfide treatments in mitigating salt damage in wheat.

Soil salinity poses a significant threat to agricultural productivity, impacting the growth and yield of wheat (Triticum aestivum L.) plants. This study investigates the potential of melatonin (MT; 100 µM) and hydrogen sulfide (H2S; 200 µM sodium hydrosulfide, NaHS) to confer the tolerance of wheat plants to 100 mM NaCl. Salinity stress induced the outburst of reactive oxygen species (ROS) resulting in damage to the chloroplast structure, growth, photosynthesis, and yield. Application of either MT or NaHS augmented the activity of antioxidant enzymes, superoxide dismutase, ascorbate peroxidase, glutathione reductase, and reduced glutathione (GSH) levels, upregulated the expression of Na+ transport genes (SOS1, SOS2, SOS3, NHX1), resulting in mitigation of salinity stress. Thus, improved stomatal behavior, gas-exchange parameters, and maintenance of chloroplast structure resulted in enhanced activity of the Calvin cycle enzymes and overall enhancement of growth, photosynthetic, and yield performance of plants under salinity stress. The use of DL-propargylglycine (PAG, an inhibitor of hydrogen sulfide biosynthesis) and p-chlorophenyl alanine (p-CPA, an inhibitor of melatonin biosynthesis) to plants under salt stress showed the comparative necessity of MT and H2S in mitigation of salinity stress. In the presence of PAG, more pronounced detrimental effects were observed than in the presence of p-CPA, emphasizing that MT was involved in mitigating salinity through various potential pathways, one of which was through H2S.