M. Nasir Khan

Interactive role of nitric oxide and calcium chloride in enhancing tolerance to salt stress

Nitric oxide (NO), a small diffusible, ubiquitous bioactive molecule, acts as prooxidant as well as antioxidant, and also regulates remarkable spectrum of plant cellular mechanisms. The present work was undertaken to investigate the role of nitric oxide donor sodium nitroprusside (SNP) and/or calcium chloride (CaCl(2)) in the tolerance of excised mustard leaves to salt stress. After 24h, salt stressed leaves treated with SNP and/or CaCl(2), showed an improvement in the activities of carbonic anhydrase (CA) and nitrate reductase (NR), and leaf chlorophyll (Chl) content, leaf relative water content (LRWC) and leaf ion concentration as compared with the leaves treated with NaCl only. Salinity stress caused a significant increase in H(2)O(2) content and membrane damage which is witnessed by enhanced levels of thiobarbituric acid reactive substances (TBARS) and electrolyte leakage. By contrast, such increases were blocked by the application of 0.2mM SNP and 10mM CaCl(2) to salt stressed leaves. Application of SNP and/or CaCl(2) alleviated NaCl stress by enhancing the activities of antioxidative enzymes viz. superoxide dismutase (SOD), catalase (CAT), peroxidase (POX), ascorbate peroxidase (APX) and glutathione reductase (GR) and by enhancing proline (Pro) and glycinebetaine (GB) accumulation with a concomitant decrease in H(2)O(2) content, TBARS and electrolyte leakage, which is manifested in the tolerance of plants to salinity stress. Moreover, application of SNP with CaCl(2) was more effective to reduce the detrimental effects of NaCl stress on excised mustard leaves. In addition to this, ameliorating effect of SNP was not effective in presence of NO scavenger cPTIO [2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide]. To put all these in a nut shell, the results advocate that SNP in association with CaCl(2) plays a role in enhancing the tolerance of plants to salt stress by improving antioxidative defence system, osmolyte accumulation and ionic homeostasis.

Morphological and physio-biochemical characterization of Brassica juncea L. Czern. & Coss. genotypes under salt stress

Abstract Soil salinity is one of the major factors responsible for the low productivity of crop plants and has become an increasing threat for agriculture. In this context, the selection of tolerant genotype/s may be one of the remedies. Keeping this in view, the effect of NaCl (0–120 mM) stress on shoot length (SL) plant−1, area (A) leaf−1, leaf area index (LAI), fresh weight (FW) and dry weight (DW) plant−1, stomatal conductance (gs), net photosynthetic rate (P N), total chlorophyll (Chl) content, malondialdehyde (MDA) content, sensitivity rate index (SRI), leaf- nitrogen (N), potassium (K) and sodium (Na) content, leaf-K/Na ratio, nitrate reductase (NR: EC.1.6.6.1) and ATP-sulphurylase (ATP-S: EC.2.7.7.4) activities and proline (Pro) and glycinebetaine (GB) content of ten genotypes of Brassica juncea L. was studied at 55 and 65 days after sowing (DAS). NaCl treatments decreased all the above parameters, except Pro, GB, MDA, Na and SRI at both stages. Salt stress resulted in accumulation of Pro and GB, in all genotypes. The magnitude of increase in both osmolytes (Pro and GB) was higher in genotype G8 than the other genotypes. Salt stress increased MDA and Na content while it decreased Chl, N and K content and K/Na ratio, Chl content, NR and ATP-S activities in all genotypes. But the magnitude of increase in MDA and Na content and decrease in SL plant−1, A leaf−1, LAI, P N, gs, Chl content and NR and ATP-S activities in genotype G8 was more than that of other genotypes. These results suggest that the salt-tolerant genotype may have better osmotic adjustment and protection from free radicals by increasing the accumulation of Pro and GB content with overproduction of N and K and higher K/Na, NR and ATP-S activities under salinity stress.

Nitrogen in relation to photosynthetic capacity and accumulation of osmoprotectant and nutrients in Brassica genotypes grown under salt stress.

Abstract Different strategies of the application of nutrients are required to overcome the adverse effects of mustard ( Brassica juncea L.) in response to NaCl stress. The objective of the present study was to determine if different added levels of nitrogen (N) in growth medium could alleviate the adverse effects of salt stress on photosynthetic capacity and accumulation of osmoprotectants and nutrients. 14 days mustard seedlings of salt-sensitive ( cv . Chuutki) and salt-tolerant ( cv. Radha) genotypes were fed with: (i) 0 mmol L −1 NaCl + 0 mg N kg −1 sand (control), (ii) 90 mmol L −1 NaCl + 30 mg N kg −1 sand, (iii) 90 mmol L −1 NaCl + 60 mg N kg −1 sand, (iv) 90 mmol L −1 NaCl + 90 mg N kg −1 sand and (v) 90 mmol L −1 NaCl + 120 mg N kg −1 sand. Under the condition of salinity stress, N application caused a significant ameliorative effect on both genotypes with respect to growth attributes [fresh weight (FW) and dry weight (DW)] and physio-biochemical parameters [percent water content (WC), net photosynthetic rate (P N ), stomatal conductance (g s ), total chlorophyll (Chl), carbonic anhydrase (CA) activity and malondialdehyde (MDA), nitrogen (N), potassium (K) and sodium (Na) contents, and K/Na ratio] and yield attributes (number of pods/plant, seeds/pod and seed yield/plant). The salt-tolerant genotype exhibited maximum value for growth, physio-biochemical and yield attributes at 60 mg N kg −1 sand than that of salt-sensitive genotype. These results suggest that application of N may ameliorate most of the attributes and prove to be a physiological remedy to increase the tolerance against the ill effects of salt stress in Brassicas .

Eutrophication: Challenges and Solutions

On the hydrological map of the world eutrophication has become the primary water quality issue. The excessive enrichment of waters with anthropogenic sources of nutrients especially nitrogen (N) and phosphorus (P) lead to the transformation of oligotrophic water bodies to mesotrophic, eutrophic, and finally hypertrophic. Mesotrophic and eutrophic phases exhibit intermediate and rich levels of nutrients and show increasing and serious water quality problems, respectively. Eutrophication restricts water use for fisheries, recreation, industry, and drinking because of increased growth of undesirable algae and aquatic weeds and the oxygen shortages caused by their death and decomposition. Associated periodic surface blooms of cyanobacteria (blue-green algae) occur in drinking water supplies and may pose a serious health hazard to animals and humans. Anthropogenic activities are the worst culprit of nutrient enrichment and root cause of eutrophication of water bodies. Excess nutrient inputs to water bodies usually come from sewage, industrial discharges, agricultural runoff, construction sites, and urban areas. Eutrophication can be minimized by regulating the nutrient sources, reducing the use of fertilizers, proper soil management practices, implementing mathematical models, phytoremediation etc. Among these, public awareness of eutrophication can play an important role in preventing the eutrophication of water bodies.

Cumulative Effect of Soil and Foliar Application of Nitrogen, Phosphorus, and Sulfur on Growth, Physico-Biochemical Parameters, Yield Attributes, and Fatty Acid Composition in Oil of Erucic Acid-Free Rapeseed-Mustard Genotypes

ABSTRACT The feasibility of split (soil + foliar) applications of nitrogen (N) and phosphorus (P) and addition of a small quantity of sulfur (S) in the spray was tested for improving performance of rapeseed-mustard genotypes in a factorial randomized field experiment. Three genotypes (two erucic acid free, viz. Brassica napus L. cv. ‘Hyola PAC – 401’ and Brassica juncea L. Czern. and Coss. cv. ‘TERI (0E) M 21-Swarna’, and one best performing high yielding Brassica juncea L. cv. ‘Rohini’ as a check) were grown with four soil (B) plus foliar (F) applications of N, P, and S with uniform basal 30 kg potassium (K) ha− 1 (K30), viz. (i) the optimum soil-applied treatment supplemented with the spray of deionized water (BN90P30 + Fw) comprising control, (ii) BN70P30 + F N20, (iii) BN70P28 + FN20P2, and (iv) BN70P28 + FN20P2S2. Soil Plus foliar application of nutrients, particularly BN70P28 + FN20P2S2, improved their performance with respect to growth characteristics (shoot length plant− 1, leaf number plant− 1, area leaf− 1, leaf area index, fresh weight plant− 1, and dry weight plant− 1), physico-biochemical parameters (net photosynthetic rate, stomatal conductance, carboxylation efficiency, water use efficiency, carbonic anhydrase activity, leaf NPK content, and N use efficiency), yield attributes (pod number plant− 1, seed number pod− 1, 1000-seed weight, seed yield ha− 1, oil content, and oil yield ha− 1), and fatty acid composition in oil of these genotypes. The cultivar ‘Hyola PAC-401’ performed best particularly with BN70P28 + FN20P2S2. The improvement in the response of genotypes to the split application of nutrients may be attributed to their ready availability through foliar application.

Nitric oxide-induced synthesis of hydrogen sulfide alleviates osmotic stress in wheat seedlings through sustaining antioxidant enzymes, osmolyte accumulation and cysteine homeostasis

Nitric oxide (NO) and hydrogen sulfide (H2S) have been shown to act as signaling molecules in various physiological processes, play significant roles in plant cellular processes, and also mediate responses to both biotic and abiotic stresses in plants. The present investigation was carried out to test the effect of exogenous NO on endogenous synthesis of H2S in osmotic-stressed wheat (Triticum aestivum L.) seedlings. The results show that application of NO to wheat seedlings, suffered from PEG8000-induced osmotic stress, considerably enhanced the activities of H2S-synthesizing enzymes l-cysteine desulfhydrase (LCD) and d-cysteine desulfhydrase (DCD) leading to enhanced level of endogenous H2S content. At the same time exogenous NO also enhanced the activity of cysteine (Cys)-synthesizing enzyme O-acetylserine(thiol)lyase (OAS-TL) and maintained Cys homeostasis under osmotic stress. NO and H2S together markedly improved the activities of antioxidant enzymes viz. ascorbate peroxidase (APX), glutathione reductase (GR), peroxidase (POX), superoxide dismutase (SOD) and catalase (CAT). Furthermore, NO and H2S caused additional accumulation of osmolytes proline (Pro) and glycine betaine (GB), all these collectively resulted in the protection of plants against osmotic stress-induced oxidative stress. On the other hand, NO scavenger cPTIO [2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide] and H2S scavenger HT (hypotaurine) invalidated the effect of NO on endogenous H2S levels and Cys homeostasis which resulted in weak protection against osmotic stress. Application of N-ethylmaleimide (NEM) suppressed GR activity and caused an increase in oxidative stress. We concluded that NO in association with endogenous H2S activates the defense system to the level required to counter osmotic stress and maintains normal functioning of cellular machinery.

Nitric oxide in plants : metabolism and role in stress physiology

Part I Nitric oxide: Metabolism, Identification and Detection 1 An Update to the Understanding of Nitric Oxide Metabolism in Plants Andrea Galatro and Susana Puntarulo 2 Biosynthesis of Nitric Oxide in Plants Tamas Roszer 3 Function of Peroxisomes as a Cellular Source of Nitric Oxide and Other Reactive Nitrogen Species Luis A. del Rio, Francisco J. Corpas, Juan B. Barroso, Eduardo Lopez-Huertas and Jose M. Palma 4 Role of Plant Mitochondria in Nitric Oxide Homeostasis During Oxygen Deficiency Halley Caixeta Oliveira and Ione Salgado 5 Production of Nitric Oxide by Marine Unicellular Red Tide Phytoplankton, Chattonella marina Daekyung Kim and Tatsuya Oda 6 Identification of Nitrosylated Proteins (SNO) and Applications in Plants Jean-Benoit Peltier, Abasse Fares and Michel Rossignol 7 Nitric Oxide: Detection Methods and Possible Roles during Jasmonate-regulated Stress Reponse Palmiro Poltronieri, Marco Taurino, Stefania Bonsegna, Stefania De Domenico and Angelo Santino 8 S-Nitrosoglutathionereductase: Key Regulator of Plant Development and Stress Response Mounira Chaki and Christian Lindermayr 9 Nitro-Fatty Acids: Synthesis, Properties and Role in Biological System Homero Rubbo and Andres Trostchansky Part II Nitric Oxide: Properties, Mode of Action and Functional Role in Stress Physiology 10 Nitric Oxide and Reactive Nitrogen Species Magdalena Arasimowicz-Jelonek, Jolanta Floryszak-Wieczorek, Dariusz Abramowski, and Karolina Izbianska 11 Nitric Oxide and Other Signaling Molecules: A Cross Talk in Response to Abiotic Stress Wei-Biao Liao and Ji-Hua Yu 12 Cytoprotective Role of Nitric Oxide under Oxidative Stress Y.S. Bakakina, E.V. Kolesneva, L.V. Dubovskaya and I.D. Volotovski 13 Phytohormones and Nitric Oxide Interactions During Abiotic Stress Responses Paulo T. Mioto, Luciano Freschi and Helenice Mercier 14 Tolerance of Plants to Abiotic Stress: A Role of Nitric Oxide and Calcium M. Nasir Khan, Firoz Mohammad, M. Mobin and M. Ali Saqib 15 Abiotic Stress Tolerance in Plants: Exploring the Role of Nitric Oxide and Humic Substances V. Mora, M. Olaetxea, E. Bacaicoa, R. Baigorri, M. Fuentes, A.M. Zamarreno and J.M. Garcia-Mina 16 Nitric Oxide in Relation to Plant Signaling and Defense Responses Mui-Yun Wong, Mansour Salati and Yee-Min Kwan 17 The Role of Nitric Oxide in Programmed Cell Death in Higher Plants Hu-Yi He, Ming-Hua Gu and Long-Fei He

Promotive effects of phosphorus on crop productivity, enzyme activities, anthraquinone and sennoside content in Cassia tora L. – a medicinal herb

Abstract The plants of Cassia tora L. were grown in pots containing soil, supplied with five levels of phosphorus: 0 (Control), 0.1, 0.2, 0.3 and 0.4 g P per kg soil. The fresh and dry weights, number of leaves and leaf-area per plant were recorded. The leaves were analyzed for inorganic elements, such as nitrogen, phosphorus, potassium and calcium. Physiological and biochemical attributes including chlorophyll and carotenoid content, nitrate reductase activity, carbonic anhydrase activity, net photosynthetic rate, stomatal conductance and transpiration rate were determined. Yield attributes including number of pods, number of seeds per pod, 100-seed weight, and seed-yield per plant were recorded. In addition, protein, total anthraquinone glycosides (in seeds) and total sennoside content (in pods) were also estimated. The results showed that phosphorus at the level of 0.3 g per kg soil proved optimum and significantly enhanced most of the attributes studied.

Tolerance of Plants to Abiotic Stress: A Role of Nitric Oxide and Calcium

Plants are continuously exposed to changing environmental conditions such as temperature, drought, salinity, heavy metals, etc., which in their extreme limits pose serious threats and set the plants with impaired growth, physiological and biochemical activities that are witnessed by the losses in crop growth and yield. However, to cope with inimical stresses plants are equipped with a series of defense system that help them to perform normally even under stressful conditions. In order to activate the defense system, signaling networks in plants trigger the molecular machinery against that particular stress condition. Calcium (Ca2+) has been proven as one of the important second messengers in eliciting responses to diverse biotic and abiotic stress signals. These stress signals elevate the cytosolic Ca2+ concentration which is sensed by Ca2+-binding proteins such as calmodulin, calcium-dependent protein kinases, and calcineurin B-like proteins that initiate downstream events leading to changes in gene expression and plant adaptation to stress tolerance. Nitric oxide (NO) is a molecule with multifaceted roles in plant growth, development, and in the tolerance of plants to biotic and abiotic stresses. Besides, NO is involved in the elevation of cytosolic Ca2+ in response to biotic and abiotic stresses. Elevated level of Ca2+ concentration not only elicits specific physiological responses to a given signal but also serve to elevate and/or maintain NO generation. The present chapter is focused on the synergistic role of NO and calcium in eliciting responses to abiotic stress signals.

Sodium nitroprusside and indole acetic acid improve the tolerance of tomato plants to heat stress by protecting against DNA damage

ABSTRACT Climate change represents a major threat to agriculture. High ambient temperatures, as a result of global warming, are currently limiting plant growth and development. The aim of the present study was to investigate the effect of sodium nitroprusside (SNP) in combination with indole acetic acid (IAA) on tomato (Lycopersicon esculentum Mill.) plants under heat stress (HS) and non-heat stress (non-HS) conditions. HS is suggested to induce the formation of reactive oxygen species, such as superoxide and hydrogen peroxide, which may lead to genotoxicity by damaging DNA, which can be detected by the comet assay (single-cell gel electrophoresis). HS substantially enhanced proline (Pro), malondialdehyde accumulation, electrolyte leakage (EL), growth reduction, and reduced physiological and biochemical parameters. However, the co-application of SNP and IAA alleviated the adverse effects of HS by promoting catalase, peroxidase, and superoxide dismutase activities and enhancing the accumulation of photosynthetic pigments (chlorophyll a and b) and Pro with a concomitant decrease in H2O2 and content, EL, and DNA damage. Conversely, the treatment of tomato plants with the NO scavenger cPTIO [2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide] along with SNP and IAA further reduced the SNP signal. Therefore, these results suggest that the application of SNP with IAA improves plant defense mechanisms against HS.