The Effects of Salt Stress on Growth Parameters and Carbohydrates Contents in Sweet Sorghum

Asaf

BioMed Research International

et al. 2019

Background Salinity is one of the major abiotic constraints that hinder health and quality of crops. Conversely, halotolerant plant growth-promoting rhizospheric (PGPR) bacteria are considered biologically safe for alleviating salinity stress. Results We isolated halotolerant PGPR strains from the rhizospheric soil of Artemisia princeps, Chenopodium ficifolium, Echinochloa crus-galli, and Oenothera biennis plants; overall, 126 strains were isolated. The plant growth-promoting traits of these isolates were studied by inoculating them with the soil used to grow soybean plants under normal and salt stress (NaCl; 200 mM) conditions. The isolates identified as positive for growth-promoting activities were subjected to molecular identification. Out of 126 isolates, five strains—Arthrobacter woluwensis (AK1), Microbacterium oxydans (AK2), Arthrobacter aurescens (AK3), Bacillus megaterium (AK4), and Bacillus aryabhattai (AK5)—were identified to be highly tolerant to salt stress and demonstrated several plant growth-promoting traits like increased production of indole-3-acetic acid (IAA), gibberellin (GA), and siderophores and increased phosphate solubilization. These strains were inoculated in the soil of soybean plants grown under salt stress (NaCl; 200 mM) and various physiological and morphological parameters of plants were studied. The results showed that the microbial inoculation elevated the antioxidant (SOD and GSH) level and K+ uptake and reduced the Na+ ion concentration. Moreover, inoculation of these microbes significantly lowered the ABA level and increased plant growth attributes and chlorophyll content in soybean plants under 200 mM NaCl stress. The salt-tolerant gene GmST1 was highly expressed with the highest expression of 42.85% in AK1-treated plants, whereas the lowest expression observed was 13.46% in AK5-treated plants. Similarly, expression of the IAA regulating gene GmLAX3 was highly depleted in salt-stressed plants by 38.92%, which was upregulated from 11.26% to 43.13% upon inoculation with the microorganism. Conclusion Our results showed that the salt stress-resistant microorganism used in these experiments could be a potential biofertilizer to mitigate the detrimental effects of salt stress in plants via regulation of phytohormones and gene expression.

Section: Discussionsupporting

confidence: 75%

Section: Introductionmentioning

confidence: 99%

Halotolerant Rhizobacterial Strains Mitigate the Adverse Effects of NaCl Stress in Soybean Seedlings

Asaf

BioMed Research International

et al. 2019

“…The maintenance of leaf tissue hydration is a behavior of plants that can adjust osmotically. Thus, some species invest in sugar synthesis or starch breakage in an attempt to mitigate damage caused by stress (Almodares et al 2008;Santelia and Lawson 2016). In this study, starch contents decreased (Fig.…”

Section: Discussionmentioning

confidence: 55%

Does Fertigation With Fish Farming Effluent Alter the Morphophysiology and Biochemistry of Lippia Gracilis (Verbenaceae)?

Neto

Morais

Dias

et al. 2021

Preprint

In order to evaluate the response mechanisms of L. gracilis fertigated with saline effluent from fish farming, L. gracilis plants were nourished with fish farming effluent with electrical conductivity of 0.45, 2.68, 4.60, 5.55 and 7.02 dS m− 1 for 60 days. The experiment was carried out in the open field using a completely randomized design with five treatments and four replicates. The salinity levels of the nutrient solution containing fish farming effluent did not affect the leaf and stem biomass production, relative water content and leaf area of the studied species. The activity of antioxidant enzymes varied when the nutrient solution salinity level was increased, which also stimulated the breakdown of starch reserves, but did not interfere with the biochemical parameters proline, photosynthetic pigments (chlorophyll a, chlorophyll b and carotenoids), levels of membrane damage and malondialdehyde, indicating that the plant showed no stress symptoms when fertigated with high-salinity effluent. The anatomy of L. gracilis leaf cross-sections shows a unistratified epidermis with glandular and non-glandular trichomes in the adaxial and abaxial sides. Plants that received only fish farming effluent (7.02 dS m− 1) showed a 25% reduction in the number of xylem bundles in the midrib region, compared to the control. The yield, chemical composition and antimicrobial activity of the essential oil extracted from L. gracilis leaves did not differ between treatments. Thus, the saline effluent from fish farming can be used in the fertigation of L. gracilis without compromising plant yield, avoiding environmental contamination with disposal in soil and/or water bodies.

Climate Change and Plant Abiotic Stress Tolerance

Metabolome Analyses for Understanding Abiotic Stress Responses in Plants to Evolve Management Strategies

Chakraborty

Pradhan

Lama

2013

Abiotic stress responses are of the utmost importance for plants because they cannot survive unless they are able to cope with environmental changes, such as high and low temperatures, drought, flooding, salinity, freezing, change in pH, strong light, UV, and heavy metals. Plants respond to various stresses at different levels, including molecular and cellular levels, as well as by modifying their metabolomes. Hence, studies on plant responses to stresses can be conducted at any of these levels to provide an understanding of the mechanisms involved. The present chapter focuses on the metabolomic approach to understand the responses of plants to different abiotic stresses, which can then be utilized to evolve strategies to combat such stress. Osmoprotectant metabolites, such as proline, glycine betaine, and polyamines, as well as carbohydrates, play important roles in the protection of plants against osmotic disbalances due to abiotic stresses. In addition, oxidative stresses are also overcome by an array of antioxidants, such as phenols, ascorbate, carotenoids, and a-tocopherol, as well as antioxidative enzymes. Signaling cascades activated during abiotic stresses lead to overexpression of protein kinases and stress proteins, and also involve molecules such as jasmonic acid and salicylic acid. Protein kinases and protein phosphatases that are encoded by large gene families often act in tandem to perform the phosphorylation and dephosphorylation leading to their activation and inactivation involved in stress signaling in plants. Analysis of microRNAs and transcriptomes has provided sufficient understanding of the gene expression levels during periods of stress. Hence, taken together, all these results can be utilized for identifying genes and/or metabolites overexpressed in tolerant species during periods of stress, and can be utilized to achieve higher tolerance and survivability during stresses. 727