Showing papers on "Shoot published in 2021"

Impact of exogenously applied trehalose on leaf biochemistry, achene yield and oil composition of sunflower under drought stress.

Abstract: This study was carried out to assess the influence of trehalose, a non-reducing disaccharide involved in improving plant stress tolerance, on two cultivars (Hysun 33 and FH 598) of sunflower (Helianthus annuus L.) grown under control and drought stress conditions. At pre-flowering stage, varying concentrations (10, 20 and 30 mM) of trehalose were applied to the foliage. Drought stress significantly suppressed the plant growth, total soluble proteins, chlorophyll, achene yield per plant, oil percentage, organic contents, as well as oil palmitic and linoleic acids in both sunflower cultivars. External application of trehalose significantly reduced RMP (relative membrane permeability), and the accumulation of H2 O2 (hydrogen peroxide), while a considerable improvement was recorded in shoot fresh and shoot and root dry weights, total soluble proteins, glycinebetaine, AsA (ascorbic acid), total phenolics, achene yield per plant, oil contents, inorganic and organic contents, and the activities of catalase (CAT), superoxide dismutase (SOD) and peroxidase (POD) enzymes under water-limited regimes. The cultivar Hysun 33 was superior to the other cultivar in plant growth, RMP, glycinebetaine, proline, achene yield per plant, oil contents, and palmitic and linoleic acids. Overall, foliar-applied trehalose improved plant growth, oxidative defense system, yield and oil composition of sunflower under drought stress conditions.

Effect of Salinity Stress on Physiological Changes in Winter and Spring Wheat

Abstract: Salinity is a leading threat to crop growth throughout the world. Salt stress induces altered physiological processes and several inhibitory effects on the growth of cereals, including wheat (Triticum aestivum L.). In this study, we determined the effects of salinity on five spring and five winter wheat genotypes seedlings. We evaluated the salt stress on root and shoot growth attributes, i.e., root length (RL), shoot length (SL), the relative growth rate of root length (RGR-RL), and shoot length (RGR-SL). The ionic content of the leaves was also measured. Physiological traits were also assessed, including stomatal conductance (gs), chlorophyll content index (CCI), and light-adapted leaf chlorophyll fluorescence, i.e., the quantum yield of photosystem II (Fv′/Fm′) and instantaneous chlorophyll fluorescence (Ft). Physiological and growth performance under salt stress (0, 100, and 200 mol/L) were explored at the seedling stage. The analysis showed that spring wheat accumulated low Na+ and high K+ in leaf blades compared with winter wheat. Among the genotypes, Sakha 8, S-24, W4909, and W4910 performed better and had improved physiological attributes (gs, Fv′/Fm′, and Ft) and seedling growth traits (RL, SL, RGR-SL, and RGR-RL), which were strongly linked with proper Na+ and K+ discrimination in leaves and the CCI in leaves. The identified genotypes could represent valuable resources for genetic improvement programs to provide a greater understanding of plant tolerance to salt stress.

Regulation of shoot branching in arabidopsis by trehalose 6-phosphate.

Abstract: Trehalose 6-phosphate (Tre6P) is a sucrose signalling metabolite that has been implicated in regulation of shoot branching, but its precise role is not understood. We expressed tagged forms of TREHALOSE-6-PHOSPHATE SYNTHASE1 (TPS1) to determine where Tre6P is synthesized in arabidopsis (Arabidopsis thaliana), and investigated the impact of localized changes in Tre6P levels, in axillary buds or vascular tissues, on shoot branching in wild-type and branching mutant backgrounds. TPS1 is expressed in axillary buds and the subtending vasculature, as well as in the leaf and stem vasculature. Expression of a heterologous Tre6P phosphatase (TPP) to lower Tre6P in axillary buds strongly delayed bud outgrowth in long days and inhibited branching in short days. TPP expression in the vasculature also delayed lateral bud outgrowth and decreased branching. Increased Tre6P in the vasculature enhanced branching and was accompanied by higher expression of FLOWERING LOCUS T (FT) and upregulation of sucrose transporters. Increased vascular Tre6P levels enhanced branching in branched1 but not in ft mutant backgrounds. These results provide direct genetic evidence of a local role for Tre6P in regulation of axillary bud outgrowth within the buds themselves, and also connect Tre6P with systemic regulation of shoot branching via FT.

PGPR-Mediated Plant Growth Attributes and Metal Extraction Ability of Sesbania sesban L. in Industrially Contaminated Soils

Abstract: The release of harmful wastes via different industrial activities is the main cause of heavy metal toxicity. The present study was conducted to assess the effects of heavy metal stress on the plant growth traits, antioxidant enzyme activities, chlorophyll content and proline content of Sesbania sesban with/without the inoculation of heavy-metal-tolerant Bacillus gibsonii and B. xiamenensis. Both PGP strains showed prominent ACC-deaminase, indole acetic acid, exopolysaccharides production and tolerance at different heavy metal concentrations (50–1000 mg/L). Further, in a pot experiment, S. sesban seeds were grown in contaminated and noncontaminated soils. After harvesting, plants were used for the further analysis of growth parameters. The experiment comprised of six different treatments. The effects of heavy metal stress and bacterial inoculation on the plant root length; shoot length; fresh and dry weight; photosynthetic pigments; proline content; antioxidant activity; and absorption of metals were observed at the end of the experiment. The results revealed that industrially contaminated soils distinctly reduced the growth of plants. However, both PGPR strains enhanced the root length up to 105% and 80%. The shoot length was increased by 133% and 75%, and the fresh weight was increased by 121% and 129%. The proline content and antioxidant enzymes posed dual effects on the plants growing in industrially contaminated soil, allowing them to cope with the metal stress, which enhanced the plant growth. The proline content was increased up to 190% and 179% by the inoculation of bacterial strains. Antioxidant enzymes, such as SOD, increased to about 216% and 245%, while POD increased up to 48% and 49%, respectively. The results clearly show that the utilized PGPR strains might be strong candidates to assist S. sesban growth under heavy metal stress conditions. We highly suggest these PGPR strains for further implementation in field experiments.

Zinc oxide nanoparticles alleviate the arsenic toxicity and decrease the accumulation of arsenic in rice ( Oryza sativa L.)

Abstract: Rice is particularly effective, compared to other cereals, at accumulating arsenic (As), a nonthreshold, class 1 human carcinogen in shoot and grain. Nano-zinc oxide is gradually used in agricultural production due to its adsorption capacity and as a nutrient element. An experiment was performed to explore the effects of zinc oxide nanoparticles (nZnO) on arsenic (As) toxicity and bioaccumulation in rice. Rice seedlings were treated with different levels of nZnO (0, 10, 20, 50, 100 mg/L) and As (0, and 2 mg/L) for 7 days. The research showed that 2 mg/L of As treatment represented a stress condition, which was evidenced by phenotypic images, seedling dry weight, chlorophyll, and antioxidant enzyme activity of rice shoot. The addition of nZnO (10–100 mg/L) enhanced the growth and photosynthesis of rice seedlings. As concentrations in the shoots and roots were decreased by a maximum of 40.7 and 31.6% compared to the control, respectively. Arsenite [As (III)] was the main species in both roots (98.5–99.5%) and shoots (95.0–99.6%) when exposed to different treatments. Phytochelatins (PCs) content up-regulated in the roots induced more As (III)-PC to be complexed and reduced As (III) mobility for transport to shoots by nZnO addition. The results confirmed that nZnO could improve rice growth and decrease As accumulation in shoots, and it performs best at a concentration of 100 mg/L.

Co-inoculation of rhizobacteria promotes growth, yield, and nutrient contents in soybean and improves soil enzymes and nutrients under drought conditions.

Abstract: Drought stress is the major abiotic factor limiting crop production. Co-inoculating crops with nitrogen fixing bacteria and plant growth-promoting rhizobacteria (PGPR) improves plant growth and increases drought tolerance in arid or semiarid areas. Soybean is a major source of high-quality protein and oil for humans. It is susceptible to drought stress conditions. The co-inoculation of drought-stressed soybean with nodulating rhizobia and root-colonizing, PGPR improves the root and the shoot growth, formation of nodules, and nitrogen fixation capacity in soybean. The present study was aimed to observe if the co-inoculation of soybean (Glycine max L. (Merr.) nodulating with Bradyrhizobium japonicum USDA110 and PGPR Pseudomonas putida NUU8 can enhance drought tolerance, nodulation, plant growth, and nutrient uptake under drought conditions. The results of the study showed that co-inoculation with B. japonicum USDA110 and P. putida NUU8 gave more benefits in nodulation and growth of soybean compared to plants inoculated with B. japonicum USDA110 alone and uninoculated control. Under drought conditions, co-inoculation of B. japonicum USDA 110 and P. putida NUU8 significantly enhanced the root length by 56%, shoot length by 33%, root dry weight by 47%, shoot dry weight by 48%, and nodule number 17% compared to the control under drought-stressed. Co-inoculation with B. japonicum, USDA 110 and P. putida NUU8 significantly enhanced plant and soil nutrients and soil enzymes compared to control under normal and drought stress conditions. The synergistic use of B. japonicum USDA110 and P. putida NUU8 improves plant growth and nodulation of soybean under drought stress conditions. The results suggested that these strains could be used to formulate a consortium of biofertilizers for sustainable production of soybean under drought-stressed field conditions.

Inoculation of Klebsiella variicola Alleviated Salt Stress and Improved Growth and Nutrients in Wheat and Maize

Abstract: Although wheat and maize are the major economically important cereal crops and staple food sources in the world, their productivity is highly affected by excess salts in soil (salinity). Applications of multifarious halophilic plant growth-promoting rhizobacteria (PGPR) in saline soil protect the plants from osmotic damages and promote plant growth through the secretion of plant growth promoting (PGP) and osmolytes. In this study, Klebsiella variicola SURYA6—a PGPR—was evaluated for plant-growth-promotion and salinity amelioration in wheat and maize, and enrichment of soil nutrients. The results of the present study revealed that K. variicola SURYA6 grows luxuriously under high salinity stress conditions and produces copious amounts of three principal salinity ameliorating traits, such as 1 aminocyclopropane-1-carboxylate deaminase (ACCD), indole-3-acetic acid (IAA), exopolysaccharides (EPS), and osmolytes—such as proline, sugars, proteins, and amino acids. The isolate also exhibited sensitivity to a wide range of antibiotics, lack of hemolytic ability, and absence of catalase and oxidase activities confirming its nonpathogenic nature. Inoculation of wheat and maize seeds with this multifarious strain, improved the physicochemical properties of soil, improved seed germination by 33.9% and 36.0%, root length by 111.0%, 35.1%, shoot height by 64.8% and 78.9%, and chlorophyll content by 68.4% and 66.7% in wheat and maize seedlings, respectively, at 45 days after sowing (DAS) under salinity stress. The improvement in plant growth can be correlated with the secretion of PGP traits and improved, uptake of minerals such as nitrogen (N), phosphorus (P), sodium (Na), potassium (K), and magnesium (Mg). While amelioration of salinity can be the result of secretion of osmolytes and the change in pH from salinity to neutrality. This inoculation also significantly improved the soil nutrients under salinity stress conditions. Inoculation of K. variicola SURYA6, resulted in more improved growth and nutrients contents in plants and enriched soil nutrients under salinity stress as compared to normal (non-saline) conditions. Such multifarious strain can serve as a potent bio-inoculant for growth promotion of wheat and maize in saline soil. However, multi-year field trials under different agro-climatic conditions are required to confirm the bio-efficacy of K. variicola SURYA6.

Hydrogen Sulfide (H 2 S) Mitigates Arsenic (As)-Induced Toxicity in Pea ( Pisum sativum L.) Plants by Regulating Osmoregulation, Antioxidant Defense System, Ascorbate Glutathione Cycle and Glyoxalase System

Abstract: Arsenic (As) being a toxic metalloid adversely affects plant growth and yield, as well as poses severe risks to human health. Hydrogen sulfide (H2S) has emerged a vital signaling molecule regulating key plant growth processes under stress conditions. However, till date little information is available regarding the role of H2S in mitigating As toxicity in pea plants. In the present study, the effect of externally applied H2S and its scavenger hypotaurine (HT) on various morphological, physiological and biochemical parameters of pea plants was evaluated. Our results showed significant decline in root length (RL), shoot length (SL), dry biomass, photosynthetic parameters such as pigment content and gas exchange characteristics in pea plants subjected to As stress. However, H2S supplementation significantly decreased As accumulation in the roots and shoot, as well as considerably enhanced growth and photosynthetic parameters. Hydrogen peroxide (H2O2), malondialdehyde (MDA) and electrolyte leakage (EL) increased significantly in the As-treated plants, while H2S supplementation considerably reduced the levels of H2O2 and MDA as well as EL. Arsenic stress accelerated the activities of antioxidant and AsA-GSH cycle enzymes except that of CAT; however, the activities of these enzymes were found to be further increased by H2S supply including that of CAT. Furthermore, ascorbate (AsA), glutathione (GSH) and methylglyoxal (MG) levels were significantly enhanced by As stress, and were further intensified in the H2S-supplemented plants. Our results demonstrated significant role of H2S in reducing As accumulation and inducing upregulation of the AsA-GSH cycle to overcome ROS-mediated oxidative damage to the cellular components of pea plants. Hence, H2S reduced oxidative damage and promoted growth of pea plants under As stress, suggesting an important role of H2S in plant priming.

Effects of phosphorus deficiency on the absorption of mineral nutrients, photosynthetic system performance and antioxidant metabolism in Citrus grandis.

Abstract: Phosphorus (P) is an essential macronutrient for plant growth, development and production. However, little is known about the effects of P deficiency on nutrient absorption, photosynthetic apparatus performance and antioxidant metabolism in citrus. Seedlings of ‘sour pummelo’ (Citrus grandis) were irrigated with a nutrient solution containing 0.2 mM (Control) or 0 mM (P deficiency) KH2PO4 until saturated every other day for 16 weeks. P deficiency significantly decreased the dry weight (DW) of leaves and stems, and increased the root/shoot ratio in C. grandis but did not affect the DW of roots. The decreased DW of leaves and stems might be induced by the decreased chlorophyll (Chl) contents and CO2 assimilation in P deficient seedlings. P deficiency heterogeneously affected the nutrient contents of leaves, stems and roots. The analysis of Chl a fluorescence transients showed that P deficiency impaired electron transport from the donor side of photosystem II (PSII) to the end acceptor side of PSI, which showed a greater impact on the performance of the donor side of PSII than that of the acceptor side of PSII and photosystem I (PSI). P deficiency increased the contents of ascorbate (ASC), H2O2 and malondialdehyde (MDA) as well as the activities of superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX), dehydroascorbate reductase (DHAR) and glutathione reductase (GR) in leaves. In contrast, P deficiency increased the ASC content, reduced the glutathione (GSH) content and the activities of SOD, CAT, APX and monodehydroascorbate reductase (MDHAR), but did not increase H2O2 production, anthocyanins and MDA content in roots. Taking these results together, we conclude that P deficiency affects nutrient absorption and lowers photosynthetic performance, leading to ROS production, which might be a crucial cause of the inhibited growth of C. grandis.

Drought and crop yield.

Abstract: Episodes of water shortage occur in most agricultural regions of the world. Their durations and intensities increase, and their seasonal timing alters with changing climate. During the ontogenic cycle of crop plants, each development stage, such as seed germination, seedling establishment, vegetative root and shoot growth, flowering, pollination and seed and fruit development, is specifically sensitive to dehydration. Desiccation threatens yield and leads to specific patterns, depending on the type of crop plant and the harvested plant parts, e.g. leafy vegetables, tubers, tap roots or fruits. This review summarizes the effects of drought stress on crop plants and relates the dehydration-dependent yield penalty to the harvested organ and tissue. The control of shoot transpiration and the reorganization of root architecture are of core importance for maintaining proper plant water relationships. Upon dehydration, the provision and partitioning of assimilates and the uptake and distribution of nutrients define remaining growth activity. Domestication of crops by selection for high yield under high input has restricted the genetic repertoire for achieving drought stress tolerance. Introgression of suitable alleles from wild relatives into commercial cultivars might improve the ability to grow with less water. Future research activities should focus more on field studies in order to generate more realistic improvements to crops. Robotic field phenotyping should be integrated into genetic mapping for the identification of relevant traits.

Role of Bacillus cereus in Improving the Growth and Phytoextractability of Brassica nigra (L.) K. Koch in Chromium Contaminated Soil.

Abstract: Plant growth-promoting rhizobacteria (PGPR) mediate heavy metal tolerance and improve phytoextraction potential in plants. The present research was conducted to find the potential of bacterial strains in improving the growth and phytoextraction abilities of Brassica nigra (L.) K. Koch. in chromium contaminated soil. In this study, a total of 15 bacterial strains were isolated from heavy metal polluted soil and were screened for their heavy metal tolerance and plant growth promotion potential. The most efficient strain was identified by 16S rRNA gene sequencing and was identified as Bacillus cereus. The isolate also showed the potential to solubilize phosphate and synthesize siderophore, phytohormones (indole acetic acid, cytokinin, and abscisic acid), and osmolyte (proline and sugar) in chromium (Cr+3) supplemented medium. The results of the present study showed that chromium stress has negative effects on seed germination and plant growth in B. nigra while inoculation of B. cereus improved plant growth and reduced chromium toxicity. The increase in seed germination percentage, shoot length, and root length was 28.07%, 35.86%, 19.11% while the fresh and dry biomass of the plant increased by 48.00% and 62.16%, respectively, as compared to the uninoculated/control plants. The photosynthetic pigments were also improved by bacterial inoculation as compared to untreated stress-exposed plants, i.e., increase in chlorophyll a, chlorophyll b, chlorophyll a + b, and carotenoid was d 25.94%, 10.65%, 20.35%, and 44.30%, respectively. Bacterial inoculation also resulted in osmotic adjustment (proline 8.76% and sugar 28.71%) and maintained the membrane stability (51.39%) which was also indicated by reduced malondialdehyde content (59.53% decrease). The antioxidant enzyme activities were also improved to 35.90% (superoxide dismutase), 59.61% (peroxide), and 33.33% (catalase) in inoculated stress-exposed plants as compared to the control plants. B. cereus inoculation also improved the uptake, bioaccumulation, and translocation of Cr in the plant. Data showed that B. cereus also increased Cr content in the root (2.71-fold) and shoot (4.01-fold), its bioaccumulation (2.71-fold in root and 4.03-fold in the shoot) and translocation (40%) was also high in B. nigra. The data revealed that B. cereus is a multifarious PGPR that efficiently tolerates heavy metal ions (Cr+3) and it can be used to enhance the growth and phytoextraction potential of B. nigra in heavy metal contaminated soil.

Tropical Bacillus Strains Inoculation Enhances Maize Root Surface Area, Dry Weight, Nutrient Uptake and Grain Yield

Abstract: The rising demand for agricultural commodities in developing countries has put increasing pressure on land resources for higher yields, with associated growth in the demand for phosphate fertilizers. However, there are a number of adverse environmental impacts associated with the use of inorganic P fertilizers that is pushing global fertilizer prices up. In this context, phosphate solubilizing microorganisms, such as Bacillus, are the most eco-friendly and inexpensive option for enhancing P availability for plants, once they are capable of transforming insoluble P into soluble (plant accessible) forms and are regarded as plant growth-promoting microorganisms. This work aimed to understand the effect of tropical Bacillus strains on maize root morphology and growth using a hydroponic system and to evaluate their performance under two phosphorus fertilization conditions in the field. Maize root was inoculated separately with six Bacillus strains and grown in nutrient solution. Several root traits, dry weight and nutrient content were measured in maize seedlings. Moreover, we measured bacterial IAA-like molecules in vitro production and evaluated inoculated maize performance under field conditions with no P added (P0) and triple superphosphate (TSP) soil fertilization. All the Bacillus strains increased shoot and total dry weight and strains B2084, B119 and B32 had the greatest performance, producing the highest biomass, shoot nutrient content and root surface area compared to other strains in hydroponics. All strains that produced IAA-like molecules demonstrated a positive effect on plant growth by stimulating root elongation. In the field experiments, strain B116 inoculation increased maize yield and P grain accumulation by around 36% and 58%, respectively, and B119 increased P grain in 21% in soils with no P added. Even in soils fertilized with TSP, maize yield increase and P grain accumulation was around 20% after inoculation with these two strains comparing to non-inoculated control. Our results indicated that maize plants inoculated with Bacillus strains capable of producing IAA-like molecules and solubilizing phosphate, presented enhanced root system, dry matter and nutrient accumulation in hydroponics and higher yield and grain P content with and without addition of phosphate fertilizer under field conditions.

Halotolerant Microbial Consortia for Sustainable Mitigation of Salinity Stress, Growth Promotion, and Mineral Uptake in Tomato Plants and Soil Nutrient Enrichment

Abstract: Salinity significantly impacts the growth, development, and reproductive biology of various crops such as vegetables. The cultivable area is reduced due to the accumulation of salts and chemicals currently in use and is not amenable to a large extent to avoid such abiotic stress factors. The addition of microbes enriches the soil without any adverse effects. The effects of microbial consortia comprising Bacillus sp., Delftia sp., Enterobacter sp., Achromobacter sp., was evaluated on the growth and mineral uptake in tomatoes (Solanum Lycopersicum L.) under salt stress and normal soil conditions. Salinity treatments comprising Ec 0, 2, 5, and 8 dS/m were established by mixing soil with seawater until the desired Ec was achieved. The seedlings were transplanted in the pots of the respective pH and were inoculated with microbial consortia. After sufficient growth, these seedlings were transplanted in soil seedling trays. The measurement of soil minerals such as Na, K, Ca, Mg, Cu, Mn, and pH and the Ec were evaluated and compared with the control 0 days, 15 days, and 35 days after inoculation. The results were found to be non-significant for the soil parameters. In the uninoculated seedlings’ (control) seedling trays, salt treatment significantly affected leaf, shoot, root dry weight, shoot height, number of secondary roots, chlorophyll, and mineral contents. While bacterized seedlings sown under saline soil significantly increased leaf (105.17%), shoot (105.62%), root (109.06%) dry weight, leaf number (75.68%), shoot length (92.95%), root length (146.14%), secondary roots (91.23%), and chlorophyll content (−61.49%) as compared to the control (without consortia). The Na and K intake were higher even in the presence of the microbes, but the beneficial effect of the microbe helps plants sustain in the saline environment. The inoculation of microbial consortia produced more secondary roots, which accumulate more minerals and transport substances to the different parts of the plant; thus, it produced higher biomass and growth. Results of the present study revealed that the treatment with microbial consortia could alleviate the deleterious effects of salinity stress and improve the growth of tomato plants under salinity stress. Microbial consortia appear to be the best alternative and cost-effective and sustainable approach for managing soil salinity and improving plant growth under salt stress conditions.

Symbiosis of AMF with growth modulation and antioxidant capacity of Caucasian Hackberry (Celtis Caucasica L.) seedlings under drought stress

Abstract: Beside climate changes, drought stress has become a serious limitated factor for plant production and seedling growth. Arbuscular mycorrhizal fungi (AMF) symbiosis has proposed to improve the growth and water efficiency under limited-water condition. For this purpose, Caucasian Hackberry (Celtis Caucasica L.) seedlings inoculate with mycorrhizal fungi Rhizophagus intraradices and Funneliformis mosseae under well-watered and water deficient conditions. The mycorrhizal and non-mycorrhizal seedlings were treated under 75 % FC (as control), 50 and 25 % FC for 90-days. The data were analyzed by using two-way ANOVA (SAS 9.2). In order to determine the significance of means, Duncan’s multiple-range test (DMRT) was performed using SAS 9.2 software at P ≤ 0.05. A principal component analysis (PCA) was conducted to assess the distribution of water and AMF treatments across a biplot figure by Past software. As well as, cluster analysis was performed using d3heatmap, dendextend, and gplots packages in R according to the Ward method to classify traits and applied treatments. The Result showed that the plant growth parameters dry shoot weight, leaf area, seedling height, dry root weight, length of root, number of secondary root, and chlorophyll content were greater in mycorrhizal seedlings in comparison with non-inoculated seedlings under normal irrigation and drought treatments. AMF symbiosis decreased H2O2 and malondialdehyde (MDA) content in leaves, while the activity of antioxidant enzymes catalase and superoxide dismutase raised in the host mycorrhiza-inoculated seedlings. The positive correlation was observed between colonization rate and plant growth as well as antioxidant enzymes activity, remarkably. These results suggest that AMF symbiosis is a potential tool to alleviating the detriment created by drought stress on Caucasian Hackberry young seedling by elevating plant growth, reducing membrane lipid peroxidation, raising cell wall stability and increasing the activity of antioxidant enzymes.

Phosphate-Dependent Regulation of Growth and Stresses Management in Plants

Abstract: The importance of phosphorus in the regulation of plant growth function is well studied. However, the role of the inorganic phosphate (Pi) molecule in the mitigation of abiotic stresses such as drought, salinity, heavy metal, heat, and acid stresses are poorly understood. We revisited peer-reviewed articles on plant growth characteristics that are phosphorus (P)-dependently regulated under the sufficient-P and low/no-P starvation alone or either combined with one of the mentioned stress. We found that the photosynthesis rate and stomatal conductance decreased under Pi-starved conditions. The total chlorophyll contents were increased in the P-deficient plants, owing to the lack of Pi molecules to sustain the photosynthesis functioning, particularly, the Rubisco and fructose-1,6-bisphosphatase function. The dry biomass of shoots, roots, and P concentrations were significantly reduced under Pi starvation with marketable effects in the cereal than in the legumes. To mitigate P stress, plants activate alternative regulatory pathways, the Pi-dependent glycolysis, and mitochondrial respiration in the cytoplasm. Plants grown under well-Pi supplementation of drought stress exhibited higher dry biomass of shoots than the no-P treated ones. The Pi supply to plants grown under heavy metals stress reduced the metal concentrations in the leaves for the cadmium (Cd) and lead (Pb), but could not prevent them from absorbing heavy metals from soils. To detoxify from heavy metal stress, plants enhance the catalase and ascorbate peroxidase activity that prevents lipid peroxidation in the leaves. The HvPIP and PHO1 genes were over-expressed under both Pi starvation alone and Pi plus drought, or Pi plus salinity stress combination, implying their key roles to mediate the stress mitigations. Agronomy Pi-based interventions to increase Pi at the on-farm levels were discussed. Revisiting the roles of P in growth and its better management in agricultural lands or where P is supplemented as fertilizer could help the plants to survive under abiotic stresses.

Translocation of heavy metals in medicinally important herbal plants growing on complex organometallic sludge of sugarcane molasses-based distillery waste

Abstract: This study aimed to assess the heavy metals accumulation patterns by some native plants such as Achyranthus aspera L., Amaranthus viridis, Basella alba L., Sesbania bispinosa, Pedalium murex L., and Momordica doica, which have been traditionally employed for medicinal and food purposes. The plants were grown on complex distillery waste containing a mixture of organometallic compounds. Results revealed bioaccumulation of Mn, Cd, Fe, Cr, Cu, As, Se, Mo, and Co in their roots, shoots, and leaves in levels higher than the surrounding sludge. A. aspera was noted as root accumulator for Mn (16.95 mg kg−1), Zn (30.12 mg kg−1), Fe (240.40 mg kg−1), Co (3.19 mg kg−1), while Se (4.07 mg kg−1), Mo (4.36 mg kg−1), was accumulated selectively in the shoot of the plant. Similarly, S. bispinosa, P. murex, and M. doica were found as root accumulators for Mn, Fe, and Ni. A. viridis accumulated Cd, Zn, and Cu in the shoot and leaves of the plant. The high bioconcentration factors (BCF) and translocation factors (TF) observed in these native plants (>1) suggested their tendency to hyperaccumulate heavy metals. The findings highlighted that these plants as a potential metal accumulator may pose health hazards and deteriorate the medicinal property if grown on such wastes.

Microalgae-cyanobacteria–based biostimulant effect on salinity tolerance mechanisms, nutrient uptake, and tomato plant growth under salt stress

Abstract: High soil salinity is a major abiotic stress affecting the growth, nutrition, development, and productivity of crops. This study investigated the modulating effect of combined microalgae-cyanobacteria extract formulations (MEF1%, MEF5%, and MEF10%) prepared from the species Dunaliella salina, Chlorella ellipsoidea, Aphanothece sp., and Arthrospira maxima, on tomato plant growth and tolerance under four NaCl concentrations (0, 80, 120, and 150 mM). MEF5% enhanced the vegetative growth of tomato plants, characterized by higher shoot and root weight and larger leaf area. According to principal component analysis (PCA), improved plant growth was closely associated with leaf photosynthetic pigments, which was mainly due to improved osmotic adjustment and ion homeostasis. Proline accumulation was significantly enhanced by MEF5%-treatment in plants grown under 120 mM and 150 mM NaCl conditions. MEF5%-treatment also significantly improved nitrogen (N), phosphorus (P), and potassium (K+) absorption in plants grown at 80 mM and 120 mM NaCl levels. Leaf lipid peroxidation through ROS oxidative stress significantly decreased with enhanced CAT and SOD activities in MEF5%-treated plants. MEF5% triggered a significant decline in fatty acid content, indicating fatty acid transformation into other lipid forms such as alkanes, which are essential in the cuticular wax synthesis of hydric stressed plants. Enhanced K+ uptake and reduced Na+/K+ ratio in the leaves of treated plants indicate MEF’s active role in reestablishing ion homeostasis. Nutrient uptake can be improved by enhanced root biomass, which subsequently increases the roots’ surface for nutrient absorption. These results indicate that MEF stimulated plant growth and tolerance responses through (i) enhanced antioxidant enzyme activities and (ii) improved root growth and nutrient uptake. Therefore, combined microalgae-cyanobacteria formulations could be another sustainable alternative to boost nutrient uptake, growth, and crop adaptability under normal and saline conditions.

Sucrose promotes stem branching through cytokinin.

Abstract: Shoot branching is an important aspect of plant architecture because it substantially affects plant biology and agricultural performance. Sugars play an important role in the induction of shoot branching in several species, including potato (Solanum tuberosum L.). However, the mechanism by which sugars affect shoot branching remains mostly unknown. In the present study, we addressed this question using sugar-mediated induction of bud outgrowth in potato stems under etiolated conditions. Our results indicate that sucrose feeding to detached stems promotes the accumulation of cytokinin (CK), as well as the expression of vacuolar invertase (VInv), an enzyme that contributes to sugar sink strength. These effects of sucrose were suppressed by CK synthesis and perception inhibitors, while CK supplied to detached stems induced bud outgrowth and VInv activity in the absence of sucrose. CK-induced bud outgrowth was suppressed in vinv mutants, which we generated by genome editing. Altogether, our results identify a branching-promoting module, and suggest that sugar-induced lateral bud outgrowth is in part promoted by the induction of CK-mediated VInv activity.

Glycine-betaine induced salinity tolerance in maize by regulating the physiological attributes, antioxidant defense system and ionic homeostasis

Abstract: The plants are exposed to different abiotic stresses, including the salinity stress (SS) that negatively affect the growth, metabolism, physiological and biochemical processes. Thus, this study investigated the effect of diverse levels of foliar-applied GB (0 control, 50 mM and 100 mM) on maize growth, membrane stability, physiological and biochemical attributes, antioxidant enzymes and nutrients accumulation under different levels of SS (i.e., control, 6 dS m-1, 12 dS m-1). Salt stress diminished the root and shoot length, root and shoot biomass, chlorophyll contents, photosynthetic rate (Pn), stomatal conductance (gs), relative water contents (RWC), soluble proteins (SP) and free amino acids; (FAA); and increased activities of antioxidant enzymes, electrical conductivity (EC) and accumulation of malondialdehyde (MDA), hydrogen peroxide (H2O2), Na+ and Cl− ions. GB application significantly increased root and shoot growth, leaves per plant, shoots length, chlorophyll contents, gs, Pn and membrane stability by reducing MDA and H2O2 accumulation. Moreover, GB also increased the SP, FAA accumulation, activities of antioxidant enzymes and Na+ and Cl- exclusion by favouring Ca2+ and K+ accumulation. In conclusion, the foliar-applied GB increased Pn, gs, ant-oxidants activities, and accumulation of SP and FAA; and reduced the accretion of Na+ and Cl− by favouring the Ca2+ and K+ accretion which in turns improved growth under SS.