Arif Shafi Wani

Role of proline under changing environments: A review

When exposed to stressful conditions, plants accumulate an array of metabolites, particularly amino acids. Amino acids have traditionally been considered as precursors to and constituents of proteins, and play an important role in plant metabolism and development. A large body of data suggests a positive correlation between proline accumulation and plant stress. Proline, an amino acid, plays a highly beneficial role in plants exposed to various stress conditions. Besides acting as an excellent osmolyte, proline plays three major roles during stress, i.e., as a metal chelator, an antioxidative defense molecule and a signaling molecule. Review of the literature indicates that a stressful environment results in an overproduction of proline in plants which in turn imparts stress tolerance by maintaining cell turgor or osmotic balance; stabilizing membranes thereby preventing electrolyte leakage; and bringing concentrations of reactive oxygen species (ROS) within normal ranges, thus preventing oxidative burst in plants. Reports indicate enhanced stress tolerance when proline is supplied exogenously at low concentrations. However, some reports indicate toxic effects of proline when supplied exogenously at higher concentrations. In this article, we review and discuss the effects of exogenous proline on plants exposed to various abiotic stresses. Numerous examples of successful application of exogenous proline to improve stress tolerance are presented. The roles played by exogenous proline under varying environments have been critically examined and reviewed.

Physiological changes induced by chromium stress in plants: an overview

This article presents an overview of the mechanism of chromium (Cr) stress in plants. Toxic effects of Cr on plant growth and development depend primarily on its valence state. Cr(VI) is highly toxic and mobile whereas Cr(III) is less toxic. Cr-induced oxidative stress involves induction of lipid peroxidation in plants that cause severe damage to cell membranes which includes degradation of photosynthetic pigments causing deterioration in growth. The potential of plants with the adequacy to accumulate or to stabilize Cr compounds for bioremediation of Cr contamination has gained engrossment in recent years.

Comparative effect of 28 homobrassinolide and salicylic acid in the amelioration of NaCl stress in Brassica juncea L.

Among various environmental stresses, salt stress is extensively damaging to major crops all over the world. An experiment was conducted to explore the role of exogenously applied 28 homobrassinolide (HBL) and salicylic acid (SA) on growth, photosynthetic parameters, transpiration and proline content of Brassica juncea L. cultivar Varuna in presence or absence of saline conditions (4.2 dsm(-1)). The leaves of 29d old plants were sprayed with distilled water, HBL and/or SA and plant responses were studied at 30 days after sowing (24 h after spray) and 45 days after sowing. The salinity significantly reduced the plant growth, gas exchange parameters but increased proline content and electrolyte leakage in the leaves. The effects were more pronounced at 30 DAS than 45 DAS. Out of the two hormones (HBL/SA) HBL excelled in its effects at both sampling stages. Toxic effects generated by salinity stress were completely overcome by the combination of the two hormones (HBL and SA) at 45 DAS.

Comparative effect of 28-homobrassinolide and 24-epibrassinolide on the growth, carbonic anhydrase activity and photosynthetic efficiency of Lycopersicon esculentum

The present piece of work highlights the comparative effects of two active forms of brassinosteroids (BRs), 28-homobrassinolide (HBL) and 24-epibrassinolide (EBL), on growth parameters, carbonic anhydrase activity and photosynthetic parameters in Lycopersicon esculentum (cv. K-21) sampled at 45 (24 h after spray) and 60 days after sowing, under natural conditions. Out of the two active forms of BR, EBL proved better than HBL in improving the above parameters, when applied as foliar spray. Of the three concentrations (10−6 M, 10−8 M or 10−10 M) of HBL and EBL, 10−8M proved best in both cases.

Protection of growth in response to 28-homobrassinolide under the stress of cadmium and salinity in wheat.

This study examines the impact of 28-homobrassinolide (HBL) in alleviating the effects of cadmium (Cd) and salinity (NaCl) on wheat plants solely and against the synergy. The surface sterilized seeds of Triticum aestivum cv. PBW-373 were sown in the soil amended either with salinity or cadmium or both. The foliage in was sprayed at 20d after sowing (DAS) both in stressed and non-stressed plants. The spray of HBL at 20 DAS increased almost all the parameters while decreased the H2O2 content and lipid peroxidation in the leaves. The presence of cadmium and/or salinity decreased the values for all the growth and photosynthetic parameters but improved the activity of antioxidant enzymes and proline content in 30d old plants. However, the ill effects observed under NaCl and/or Cd treatment were completely overcomed by the spray of HBL to the plants at 20d stage. The spray of HBL to stressed plants further increased the antioxidant enzyme activities and proline content thereby giving tolerance to the plants against the stress.

Salicylic acids: Local, systemic or inter-systemic regulators?

Salicylic acid is well known phytohormone, emerging recently as a new paradigm of an array of manifestations of growth regulators. The area unleashed yet encompassed the applied agriculture sector to find the roles to strengthen the crops against plethora of abiotic and biotic stresses. The skipped part of integrated picture, however, was the evolutionary insight of salicylic acid to either allow or discard the microbial invasion depending upon various internal factors of two interactants under the prevailing external conditions. The metabolic status that allows the host invasion either as pathogenesis or symbiosis with possible intermediary stages in close systems has been tried to underpin here.

Impact of sodium nitroprusside on nitrate reductase, proline content, and antioxidant system in tomato under salinity stress

The present study was carried out to elucidate the protective role of sodium nitroprusside (SNP) against salt (NaCl) stress given as seed soaking in tomato (Solanum lycopersicum Mill. cv. K-21). For this experiment prior to sowing, the surface sterilized tomato seeds were soaked in different concentrations of NaCl solution (50, 100, and 150 mM) for 8 hours. Some NaCl soaked seeds were then transferred to the 10−5 M of SNP solution for 8 hours. The plants were sampled at 60 DAS to assess the nitrate reductase activity, proline content and the activities of antioxidant enzymes. The antioxidant enzyme activity and proline content increased in the plants where SNP was applied as a follow up treatment of the NaCl as seed soaking over the control plants thereby providing stress tolerance to the plants. In case of the nitrate reductase activity the toxic effects generated by the lowest concentration of NaCl (50 mM) was completely neutralized by SNP and partly at higher concentrations (100/150 mM). These results suggest that nitric oxide can be used as a stress alleviator in plants which are grown in the soil contaminated with salinity stress.

Screening of salt-tolerant genotypes of Brassica juncea based on photosynthetic attributes

Abstract The present experiment was conducted to evaluate salt tolerance in varieties of Indian mustard (Brassica juncea). Sterilized seeds were grown under natural environment in pots containing soil amended with 1.4 (control), 2.8, 4.2 and 5.6 dSm−1 NaCl and sampled at 30 days after sowing. Growth was recorded in terms of length, fresh mass, dry mass and leaf area of plants, which was drastically reduced in Chapka Rohini, while there was little effect of NaCl treatment on Varuna. In Chapka Rohini, a rise in the level of proline was observed which followed the decline in protein content. The declines in net photosynthesis and other related parameters have been attributed to this decline. From the results, it could be suggested that Varuna is salt-tolerant while Chapka Rohini is the salt-sensitive variety of mustard among the screened genotypes. Photosynthetic capacity is a major factor in conferring the salt-sensitiveness and tolerance in plant varieties.

Nitric Oxide Effects on Photosynthetic Rate, Growth, and Antioxidant Activity in Tomato

Nitric oxide has recently been recognized as a new growth regulator in plants. Its effects on plant functions are not clear. A study was conducted to investigate the growth-promoting effects of nitric oxide in Solanum lycopersicum L., cv. K-21, under net house conditions. Surface-sterilized seeds were soaked for 8 hours in 10−6, 10−5, or 10−4 M sodium nitroprusside (SNP), a nitric oxide donor. Resulting plants were sampled at 45 and 60 days after sowing to assess effects on growth as well as photosynthetic and biochemical parameters. The 10−5 M SNP was best followed by the 10−4 and 10−6 M concentrations. The favorable effect was attributed to NO-induced biosynthesis of proline and a rise in activity of the antioxidant system.

Regulation of growth and photosynthetic parameters by salicylic acid and calcium in Brassica juncea under cadmium stress.

Abstract Cadmium, a non-essential and toxic metal, negatively affects plant growth and productivity, and alters the plant’s physiological processes necessary for its survival. The present study was designed to explore the individual and combined effects of calcium and salicylic acid (SA) on the morphology and physiology of Brassica juncea L. cv. Varuna under cadmium stress. The application of calcium (2 mM) through the soil and/or SA (10-5 M) as foliar spray enhanced the growth, photosynthetic parameters, and proline content determined after 45 days of treatment. The application of cadmium (6 mg kg-1) through the soil was toxic and decreased both growth and the photosynthetic parameters. The application of calcium and SA in combination was most effective in alleviating the harmful effects of cadmium on growth and photosynthesis. Calcium and SA clearly induced plant protection mechanisms by enhancing proline and chlorophyll accumulation in the leaves.