Mohamed H. Al-Whaibi

Role of nitric oxide in tolerance of plants to abiotic stress

Nitric oxide (NO) has now gained significant place in plant science, mainly due to its properties (free radical, small size, no charge, short-lived, and highly diffusible across biological membranes) and multifunctional roles in plant growth, development, and regulation of remarkable spectrum of plant cellular mechanisms. In the last few years, the role of NO in tolerance of plants to abiotic stress has established much consideration. As it is evident from the present review, recent progress on NO potentiality in tolerance of plants to environmental stresses has been impressive. These investigations suggest that NO, itself, possesses antioxidant properties and might act as a signal in activating ROS-scavenging enzyme activities under abiotic stress. NO plays an important role in resistance to salt, drought, temperature (high and low), UV-B, and heavy metal stress. Rapidly increasing evidences indicate that NO is essentially involve in several physiological processes; however, there has been much disagreement regarding the mechanism(s) by which NO reduces abiotic stress.

Effect of calcium and potassium on antioxidant system of Vicia faba L. Under cadmium stress.

Cadmium (Cd) in soil poses a major threat to plant growth and productivity. In the present experiment, we studied the effect of calcium (Ca2+) and/or potassium (K+) on the antioxidant system, accumulation of proline (Pro), malondialdehyde (MDA), and content of photosynthetic pigments, cadmium (Cd) and nutrients, i.e., Ca2+ and K+ in leaf of Vicia faba L. (cv. TARA) under Cd stress. Plants grown in the presence of Cd exhibited reduced growth traits [root length (RL) plant−1, shoot length (SL) plant−1, root fresh weight (RFW) plant−1, shoot fresh weight (SFW) plant−1, root dry weight (RDW) plant−1 and shoot dry weight (SDW) plant−1] and concentration of Ca2+, K+, Chlorophyll (Chl) a and Chl b content, except content of MDA, Cd and (Pro). The antioxidant enzymes [peroxidase (POD) and superoxide dismutase (SOD)] slightly increased as compared to control under Cd stress. However, a significant improvement was observed in all growth traits and content of Ca2+, K+, Chl a, Chl b, Pro and activity of antioxidant enzymes catalase (CAT), POD and SOD in plants subjected to Ca2+ and/or K+. The maximum alleviating effect was recorded in the plants grown in medium containing Ca2+ and K+ together. This study indicates that the application of Ca2+ and/or K+ had a significant and synergistic effect on plant growth. Also, application of Ca2+ and/or K+ was highly effective against the toxicity of Cd by improving activity of antioxidant enzymes and solute that led to the enhanced plant growth of faba bean plants.

Interactive effect of calcium and gibberellin on nickel tolerance in relation to antioxidant systems in Triticum aestivum L.

Nickel toxicity affects many metabolic facets of plants and induces anatomical and morphological changes resulting in reduced growth and productivity. To overcome the damaging effects of nickel (Ni) stress, different strategies of the application of nutrients with plant hormones are being adopted. The present experiment was carried out to assess the growth and physiological response of wheat plant (Triticum aestivum L.) cv. Samma to pre-sowing seed treatment with GA3 alone as well as in combination with Ca2+ and/or Ni stress. The pre-sowing seed treatment of Ni decreased all the growth characteristics (plant height, root length, fresh, and dry weight) as well as chlorophyll (Chl) content and enzyme carbonic anhydrase (CA: E.C. 4.2.1.1) activity. However, an escalation was recorded in malondialdehyde content and electrolyte leakage in plants raised from seed soaked with Ni alone. Moreover, all the growth parameters and physiological attributes (Chl content, proline (Pro) content, CA, peroxidase (E.C.1.11.1.7), catalase (E.C. 1.11.1.6), superoxide dismutase (E.C. 1.15.1.1), ascorbate peroxidase (E.C. 1.11.1.11), and glutathione reductase (E.C. 1.6.4.2) were enhanced in the plants developed from the seeds soaked with the combination of GA3 (10−6 M), Ca2+, and Ni. The present study showed that pre-sowing seed treatment of GA3 with Ca2+ was more capable in mitigation of adverse effect of Ni toxicity by improving the antioxidant system and Pro accumulation.

Nano‐silicon dioxide mitigates the adverse effects of salt stress on Cucurbita pepo L

Research into nanotechnology, an emerging science, has advanced in almost all fields of technology. The aim of the present study was to evaluate the role of nano-silicon dioxide (nano-SiO2 ) in plant resistance to salt stress through improvement of the antioxidant system of squash (Cucurbita pepo L. cv. white bush marrow). Seeds treated with NaCl showed reduced germination percentage, vigor, length, and fresh and dry weights of the roots and shoots. However, nano-SiO2 improved seed germination and growth characteristics by reducing malondialdehyde and hydrogen peroxide levels as well as electrolyte leakage. In addition, application of nano-SiO2 reduced chlorophyll degradation and enhanced the net photosynthetic rate (Pn ), stomatal conductance (gs ), transpiration rate, and water use efficiency. The increase in plant germination and growth characteristics through application of nano-SiO2 might reflect a reduction in oxidative damage as a result of the expression of antioxidant enzymes, such as catalase, peroxidase, superoxide dismutase, glutathione reductase, and ascorbate peroxidase. These results indicate that nano-SiO2 may improve defense mechanisms of plants against salt stress toxicity by augmenting the Pn , gs , transpiration rate, water use efficiency, total chlorophyll, proline, and carbonic anhydrase activity in the leaves of plants.

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 .

Current status of the production of high temperature tolerant transgenic crops for cultivation in warmer climates.

Climate change is resulting in heightened incidences of plant heat stress episodes. Production of transgenic crops with enhanced heat stress tolerance is a highly desired agronomic trait for the sustainability of food production in 21st century. We review the current status of our understanding of the high temperature stress response of plants. We specifically deliberate on the progress made in altering levels of heat shock proteins (Hsp100, Hsp70/Hsp40 and sHsps), heat shock factors and specific metabolic proteins in improving plant tolerance to heat stress by transgenic approach.

Response of Different Genotypes of Faba Bean Plant to Drought Stress

Drought stress is one of the major abiotic stresses that are a threat to crop production worldwide. Drought stress impairs the plants growth and yield. Therefore, the aim of the present experiment was to select the tolerant genotype/s on the basis of moprpho-physiological and biochemical characteristics of 10 Vicia faba genotypes (Zafar 1, Zafar 2, Shebam, Makamora, Espan, Giza Blanka, Giza 3, C4, C5 and G853) under drought stress. We studied the effect of different levels of drought stress i.e., (i) normal irrigation (ii) mild stress (iii) moderate stress, and (iv) severe stress on plant height (PH) plant−1, fresh weight (FW) and dry weight (DW) plant−1, area leaf−1, leaf relative water content (RWC), proline (Pro) content, total chlorophyll (Total Chl) content, electrolyte leakage (EL), malondialdehyde (MDA), hydrogen peroxide (H2O2) content, and activities of catalase (CAT), peroxidase (POD) and superoxide dismutase (SOD) of genotypes of faba bean. Drought stress reduced all growth parameters and Total Chl content of all genotypes. However, the deteriorating effect of drought stress on the growth performance of genotypes “C5” and “Zafar 1” were relatively low due to its better antioxidant enzymes activities (CAT, POD and SOD), and accumulation of Pro and Total Chl, and leaf RWC. In the study, genotype “C5” and “Zafar 1” were found to be relatively tolerant to drought stress and genotypes “G853” and “C4” were sensitive to drought stress.

Morphological and physiological characterization of different genotypes of faba bean under heat stress

Heat stress (HS) is the major constraint to crop productivity worldwide. The objective of the present experiment was to select the tolerant and sensitive genotype(s) on the basis of morpho-physiological and biochemical characteristics of ten Vicia faba genotypes. These genotypes were as follows: Zafar 1, Zafar 2, Shebam 1, Makamora, Espan, Giza Blanka, Giza 3, C4, C5 and G853. The experimental work was undertaken to study the effects of different levels of temperature (control, mild, and modest) on plant height (PH) plant−1, fresh weight (FW) and dry weight (DW) plant−1, area leaf−1, content of leaf relative water (RWC), proline content (Pro) and total chlorophyll (Total Chl), electrolyte leakage (EL), malondialdehyde level (MDA), hydrogen peroxide (H2O2), and activities of catalase (CAT), peroxidase (POD) and superoxide dismutase (SOD) enzymes. HS significantly affected growth performance of all genotypes. However, the magnitude of reduction in genotypes ‘C5’ was relatively low, possibly due to its better antioxidant activities (CAT, POD and SOD), and accumulation of Pro and Total Chl, and leaf RWC. In the study, ‘C5’ was noted to be the most HS tolerant and ‘Espan’ most HS sensitive genotypes. It was concluded that the heat-tolerant genotypes may have better osmotic adjustment and protection from free radicals by increasing the accumulation of Pro content with increased activities of antioxidant enzyme.

Role of Nanoparticles in Plants

Nanotechnology opens a large scope of novel application in the fields of biotechnology and agricultural industries, because nanoparticles (NPs) have unique physicochemical properties, i.e., high surface area, high reactivity, tunable pore size, and particle morphology. Nanoparticles can serve as “magic bullets”, containing herbicides, nano-pesticide fertilizers, or genes, which target specific cellular organelles in plant to release their content. Despite the plenty of information available on the toxicity of nanoparticles to plant system, few studies have been conducted on mechanisms, by which nanoparticles exert their effect on plant growth and development. Therefore, the present review highlights the key role of nanoparticles in plants. Moreover, nanoscience contributes new ideas leading us to understand the suitable mode of action of nanoparticles in plants. The appropriate elucidation of physiological, biochemical, and molecular mechanism of nanoparticles in plant leads to better plant growth and development.

Genetic approaches for breeding heat stress tolerance in faba bean (Vicia faba L.)

Vicia faba L. (faba bean) is an important legume and is cultivated essentially as a cool-season crop. Changes in sowing dates and lack of precipitation expose faba bean crop to drought and heat stresses. The gradual rise in global temperatures owing to climate change is likely to exacerbate the detrimental effects of hot and dry climatic conditions on faba bean cultivation. High temperature stress is particularly damaging to faba bean during the flowering period, when the viability of pollen is critical for successful reproduction. Recent studies have shown that maintenance of protein homeostasis through synthesis of heat shock proteins plays a key role in the heat response of plants. To date, there has been no significant work linking the heat response of faba bean to the repertoire of its heat shock proteins. While quantitative trait loci have been identified for resistance against biotic stresses in faba bean, there is no parallel success with abiotic stresses in this species. Programs aiming at genetic improvement of the heat/drought resistance of this crop by both conventional breeding and molecular breeding methods are hampered because of the large and majorly ill-analyzed genome of faba bean plants. Likewise, molecular and biotechnology-related tools are poorly developed for faba bean; as a result, the fruits of transgenic research developed with model plant species are not reaching this crop. While specifically discussing the prospects for the genetic improvement of faba bean against heat and drought stresses, we highlight the areas of research which need to be strengthened on faba bean.