Plants are frequently exposed to a plethora of unfavorable or even adverse environmental conditions, termed as abiotic stresses (such as salinity, drought, heat, cold, flooding, heavy metals, ozone, UV radiation, etc.) and thus they pose serious threats to the sustainability of crop yield. Soil salinity, one of the most severe abiotic stresses, limits the production of about 6 % of the world’s total land and 20 % of irrigated land (17 % of total cultivated areas) and negatively affects crop production worldwide. On the other hand, increased salinity of agricultural land is expected to have destructive global effects, resulting in up to 50 % land loss by the next couple of decades. The adverse effects of salinity have been ascribed mainly to an increase in sodium (Na+) and chloride (Cl–) ions and hence these ions produce the critical conditions for plant survival by intercepting different plant mechanisms. Both Na+ and Cl– produce many physiological disorders in plants but Cl– is the most dangerous. A plant’s response to salt stress depends on the genotype, developmental stage, as well as the intensity and duration of the stress. Increased salinity has diverse effects on the physiology of plants grown in saline conditions and in response to major factors like osmotic stress, ion-specificity, nutritional and hormonal imbalance, and oxidative damage. In addition to upper plant parts, salinity also affects root growth and physiology and their function in nutrient uptake. The outcome of these effects may cause the disorganization of cellular membranes, inhibit photosynthesis, generate toxic metabolites and decline nutrient absorption, ultimately leading to plant death. In recent decades, exogenous protectants such as osmoprotectants, phytohormones, signaling molecules, polyamines, antioxidants and various trace elements have been found effective in plants in mitigating the salt induced damages. These protectants showed the capacity to enhance the plants’ growth, yield as well as stress tolerance under salinity. In this chapter we attempt to summarize differential responses of plants to salinity with special reference to growth, physiology and yield. Further, we have discussed the progress made in using exogenous protectants to mitigate salt-induced damages in plants.

https://www.springer.com/cda/content/document/cda_downloaddocument/9781461447467-c1.pdf

Plant Response to Salt Stress and Role of Exogenous Protectants to Mitigate Salt-Induced Damages

Salt stress is one of the major abiotic stresses limiting crop production especially in arid and semi-arid regions. It is reported that about 7 % of the total earths land and 20 % of the total arable area are affected by high salt contents. Reclamation of salt affected soils is necessary as the salt is engulfing the cultivable land day by day. The earliest response of plants to salt stress is reduction in the rate of leaf surface expansion followed by cessation of expansion as the stress intensifies but growth resumes when the stress is relieved. Metabolic processes like photosynthesis, protein synthesis and lipid metabolisms are affected due to salt stress. Salinity is responsible for different types of stresses like, osmotic stress, ionic stress, oxidative stress and hormonal imbalances. The osmotic stress is caused by the excess of Na+ and Cl− ions in the soil that decrease the osmotic potential and hampers the water uptake and nutrients. Low molecular mass compounds known as compatible solutes is accumulated under salt stress. These compatible solutes include proline, glycinebetaine, sugars, proteins, polyols, etc. They do not interfere with the normal biochemical reactions and helps the plants in building the resistance against the stress.

Salt Stress: Causes, Types and Responses of Plants

Salinity is one of the major abiotic factors affecting alfalfa productivity. Identifying genes that control this complex trait will provide critical insights for alfalfa breeding programs. To date, no studies have been published on a deep sequencing-based profiling of the alfalfa transcriptome in response to salinity stress. Observations gathered through research on reference genomes may not always be applicable to alfalfa. In this work, Illumina RNA-sequencing was performed in two alfalfa genotypes contrasting in salt tolerance, in order to estimate a broad spectrum of genes affected by salt stress. A total of 367,619,586 short reads were generated from cDNA libraries originated from roots of both lines. More than 60,000 tentative consensus sequences (TCs) were obtained and, among them, 74.5% had a significant similarity to proteins in the NCBI database. Mining of simple sequence repeats (SSRs) from all TCs revealed 6,496 SSRs belonging to 3,183 annotated unigenes. Bioinformatics analysis showed that the expression of 1,165 genes, including 86 transcription factors (TFs), was significantly altered under salt stress. About 40% of differentially expressed genes were assigned to known gene ontology (GO) categories using Arabidopsis GO. A random check of differentially expressed genes by quantitative real-time PCR confirmed the bioinformatic analysis of the RNA-seq data. A number of salt-responsive genes in both tested genotypes were identified and assigned to functional classes, and gene candidates with roles in the adaptation to salinity were proposed. Alfalfa-specific data on salt-responsive genes obtained in this work will be useful in understanding the molecular mechanisms of salinity tolerance in alfalfa.

/pdf/analysis-of-the-alfalfa-root-transcriptome-in-response-to-2mof2ja6h7.pdf

Analysis of the Alfalfa Root Transcriptome in Response to Salinity Stress

http://fac.ksu.edu.sa/sites/default/files/1-s2.0-s1319562x15000625-main.pdf

Enhancing growth performance and systemic acquired resistance of medicinal plant Sesbania sesban (L.) Merr using arbuscular mycorrhizal fungi under salt stress

The effects of salt and water stress on growth and several stress markers were investigated in cherry tomato plants. Some growth parameters (stem length and number of leaves) and chlorophyll contents were determined every third day during plant growth, and leaf material was collected after 25 and 33 days of treatment. Both stresses inhibited plant growth; chlorophyll levels, however, decreased only in response to high NaCl concentrations. Proline contents largely increased in leaves of stressed plants, reaching levels high enough to play a major role in cellular osmotic adjustment. Despite reports indicating that tomato does not synthesize glycine betaine, the stress-induced accumulation of this osmolyte was detected in cherry tomato, albeit at lower concentration than that of proline. Therefore, it appears that the plants are able to synthesise glycine betaine as a secondary osmolyte under strong stress conditions. Total sugars levels, on the contrary, decreased in stress-treated plants. Both stress treatments caused secondary oxidative stress in the plants, as indicated by a significant increase in malondialdehyde (MDA) contents. Water stress led to an increase in total phenolics and flavonoid contents and a reduction of carotenoid levels in the leaves; flavonoids also increased under high salinity conditions.

/pdf/effects-of-salt-and-water-stress-on-plant-growth-and-on-3ligcdcg7c.pdf

Effects of Salt and Water Stress on Plant Growth and on Accumulation of Osmolytes and Antioxidant Compounds in Cherry Tomato

Tomato cultivar PKM 1 were subjected to 25, 50, 100, 150 and 200 mM NaCl stress and response of tomato plant to saltstress were determined by assessing the variability of different biochemical parameters In this present study endogenouscontent of growth hormones IAA and ABA in leaves, proline and mineral (Na+ and K+) content in leaves and maturefruits were estimated Leaf area and dry matter content of tomato fruits under salt stress were determined to study theeffect of salinity on photosynthetic yield Results showed that leaf area and dry matter content of tomato fruits decreasedwith application of elevated salt stress, however endogenous content of IAA, ABA and proline was found to beincreasing with increase in salt treatment Application of NaCl caused increase in Na+ content, while K+ content andK+/Na+ ratio decreased with increase in salt stress Another striking point is that increase in proline and Na+ contentwas more in leaves than fruits, which suggests that leaves are more sensitive than fruitsKeyword: Salt stress, IAA, ABA, Proline, Na+, dry matter

http://www.thejaps.org.pk/docs/v-22-1/25.pdf

The effect of salinity on growth, hormones and mineral elements in leaf and fruit of tomato cultivar PKM1.

An exhaust valve is the important component in the engine system due to its direct involvement in the combustion and experiencing the high temperature and pressure from the hot gases during the exhaust stroke based on the valve timing for opening and closing. Because of this exposure to exhaust, high thermal loads are induced which leads to the failure of the valve. Therefore, a cooling provision is must to reduce the temperatures due to heat transfer effect or to increase the heat dissipation rate through valve by maintaining it at optimum thermal conditions. The cooling provisions are by filling the valve with sodium making valve hollow inside or by using the thermal barrier coatings on the outer surface of valve. In this an attempt is made to study the importance of cooling provision by doing thermal analysis on the valve geometry with different approaches under full load conditions of engine. The valve geometry is modelled using CAD software and the thermal analysis at steady state is done using Ansys under FEA basis. The expected results are temperature variation, heat flux, rate of heat transfer.

https://mapletreejournals.com/index.php/IRJAT/article/download/106/61

Thermal Analysis on Exhaust Valve with Thermal Barrier Material

Objective: Amorphophallus commutatus var. wayanadensis (ACW) is exclusive endemic of Wayanad has been used among the traditional medicinal healers of tribal communities of Wayanad for the treatment of various ailments. Our aim of the study is to evaluate the toxicity profile of ACW is by acute and sub-acute in rodents. Methods: In acute toxicity studies, mice were orally administered of single doses of 1000 and 2000mg/kg of methanolic and aqueous extract and sub-acute toxicity studies were performed by administration of 200 and 400mg/kg orally for 28 days. Results: In acute toxicity studies, administration of methanolic and aqueous extract didn’t observe any signs of mortality or toxicity upto 2000mg/kg body weight. No significant change in the physical, biochemical, hematological and histopathology analysis were observed for methanolic and aqueous extracts by sub-acute toxicity studies. Conclusion: The methanolic and aqueous extract of Amorphophallus commutatus var. wayanadensis is relatively safe for long term oral administration fulfilling the basic priority for its use in traditional medicinal therapies.

Toxicological profiling of methanolic and aqueous extracts of amorphophallus commutatus var. wayanadensis - endangered medicinal plant in rodent models

Kerala is endowed with rich biodiversity of medicinal plants which are widely used in various traditional medicinal systems like Ayurveda which are potential sources of bioactive constituents with effective and safer drugs. The present study is to evaluate the antibacterial, antioxidant and antiproliferative activity of traditional medicinal plants Biophytum sensitivum (L.) DC, Curculiogo orchioides Gaertn. and Cynodon dactylon (L.) Pers. The petroleum ether extract of Curculiogo orchioides showed significant antibacterial activity against pathogenic strains of bacteria. Among the other extracts methanolic extract of Curculiogo orchioides showed higher phenolic and flavonoid content and significant DPPH scavenging and reducing power activity. The antiproliferative activity was tested against Hep G2 (hepatocellular liver carcinoma) in which methanolic extract of Biophytum sensitivum and Curculiogo orchioides showed strong anticancer activity with an IC50 108.72 and 127.12µg/ml respectively. Our study confirmed the ethanobotanical and traditional medicinal usage of the three medicinal plants Biophytum sensitivum, Curculiogo orchioides and Cynodon dactylon.

/pdf/antioxidant-antibacterial-and-anti-proliferative-activity-3pldhhdms2.pdf

Merlene Ann Babu

Papers

The effect of salinity on growth, hormones and mineral elements in leaf and fruit of tomato cultivar PKM1.

Thermal Analysis on Exhaust Valve with Thermal Barrier Material

Toxicological profiling of methanolic and aqueous extracts of amorphophallus commutatus var. wayanadensis - endangered medicinal plant in rodent models

Antioxidant, Antibacterial and Anti-Proliferative Activity and Phytochemical Analysis of Selected Medicinal Plants from Dasapushpam of Kerala

Design and optimization of linear Fresnel reflector concentrating solar system using particle swarm optimization algorithms