Mohd Irfan

Physiological and biochemical changes in plants under waterlogging

Waterlogging usually results from overuse and/or poor management of irrigation water and is a serious constraint with damaging effects. The rapidly depleting oxygen from submerged root zone is sensed and plant adjusts expressing anaerobic proteins. Plant cells shift their metabolism towards low energy yielding anaerobic fermentation pathways in the absence of oxygen. Structural modifications are also induced as aerenchyma formation and adventitious rootings, etc. Studies at molecular and biochemical levels to facilitate early perception and subsequent responses have also been worked out to produce resistant transgenic plants. This review explores the sequential changes of plant responses at different levels regarding their defense strategies and efforts made to enhance them, tailoring crucial regulators so that they can withstand waterlogging stress.

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.

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.

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.

Growth, photosynthesis, and antioxidant responses of Vigna unguiculata L. treated with hydrogen peroxide

Abstract Cowpea (Vigna unguiculata L.) is an important legume well grown in semiarid and arid environment. Hydrogen peroxide solutions (0.1, 0.5, 1.0, and 1.5 mM) have been used to optimize growth and photosynthetic performance of cowpea plant at two growth stages [30 and 45 DAS (days of sowing)]. Foliar application of H2O2 at 0.5 > 1.0 mM solution at 29 DAS optimally promoted the photosynthetic attributes [leaf chlorophyll content, net photosynthetic rate (PN), water use efficiency, and maximum quantum yield of PSII (Fv/Fm)] and growth performance [root and shoot length; fresh and dry weight] of plants where the responses were more significant at the later growth stage. It was favored by activity of enzymes as carbonic anhydrase [CA; E.C. 4.2.1.1] and nitrate reductase [NR, E.C. 1.6.6.1] and those of antioxidant enzymes viz. peroxidase [POX; EC 1.11.1.7], catalase [CAT; EC 1.11.1.6], and superoxide dismutase [SOD; EC 1.15.1.1] and leaf proline content. Strengthened root system and antioxidant activity, particularly leaf proline level appeared to be the key factor for efficient photosynthesis and growth responses.

Alleviation of Salinity Stress With Sodium Nitroprusside in Tomato

Tomato (Solanum lycopersicum L.) is moderately salt sensitive and yield can be reduced by 50% when exposed to a 7.5 dS·m−1 electrical conductivity (EC) saline solution. The response of tomato, cv. K-21, to presowing seed treatment with sodium chloride (NaCl) and sodium nitroprusside (SNP) was investigated. Before sowing, surface-sterilized seed of tomato were soaked in 50, 100, or 150 mM NaCl for 8 h and then transferred to a 10−5 M solution of SNP for 8 h. Plants were sampled at 45 and 60 days after sowing (DAS) to assess carbonic anhydrase activity (E.C. 4.2.1.1), relative water content, photosynthetic attributes, and growth parameters. Activity of carbonic anhydrase and all other parameters was increased by SNP application following the NaCl treatment. Detrimental effects generated by the 50 mM NaCl concentration were completely neutralized by SNP at 60 DAS, whereas those of highest NaCl concentration were not reversed by SNP at both sampling stages. It appears that SNP alleviates salinity stress up to 50 mM NaCl.

Photosynthetic variation and yield attributes of two mustard varieties against cadmium phytotoxicity

Abstract Excess cadmium accumulation in shoot decreases the photosynthetic attributes and the activity of carbonic anhydrase (CA; E.C. 4.2.1.1) thereby retarding plant growth metabolism, in a cultivar dependent manner. Two mustard (Brassica juncea) varieties were treated with increasing cadmium doses (0, 25, 50 or 100 mg CdCl2 kg−1 of soil) in the soil in a net house. The photosynthetic features, activity of CA, and the yield attributes were recorded in association with morphological characters. A clear-cut difference in these features was noted among the varieties, where Varuna excelled in its resistance to the cadmium toxicity with better growth and yield, at harvest.

Overlapping Horizons of Salicylic Acid under Different Stresses

Salicylic acid (SA) is an established plant hormone with its multifaceted, pleiotropic effects within and beyond the plant system, under stress and non-stress conditions. SA has been appreciated in regulating biotic stress locally under symbiotic and pathogenic and non-pathogenic invasion to induced systemic resistance (ISR) and systemic acquired resistance (SAR) eliciting an array of secondary molecules and a different profile of functional proteins. However, systemic knowledge of cause and consequence of indigenous inbuilt of SA and precise details of its regulation mechanism are still not clear.This chapter investigates the indigenous accumulation and overlapping roles of SA under different environmental and physiological conditions, highlighting its recently updated roles in regulating plants.