Mechanisms and Role of Nitric Oxide in Phytotoxicity-Mitigation of Copper

Abstract

Phytotoxicity of metals significantly contributes to the major loss in agricultural productivity. Among all the metals, copper (Cu) is one of essential metals, where it exhibits toxicity only at its supra-optimal level. Elevated Cu levels affect plants developmental processes from initiation of seed germination to the senescence, photosynthetic functions, growth and productivity. The use of plant growth regulators/phytohormones and other signaling molecules is one of major approaches for reversing Cu-toxicity in plants. Nitric oxide (NO) is a versatile and bioactive gaseous signaling molecule, involved in major physiological and molecular processes in plants. NO modulates responses of plants grown under optimal conditions or to multiple stress factors including elevated Cu levels. The available literature in this context is centered mainly on the role of NO in combating Cu stress with partial discussion on underlying mechanisms. Considering the recent reports, this paper: (a) overviews Cu uptake and transport; (b) highlights the major aspects of Cu-toxicity on germination, photosynthesis, growth, phenotypic changes and nutrient-use-efficiency; (c) updates on NO as a major signaling molecule; and (d) critically appraises the Cu-significance and mechanisms underlying NO-mediated alleviation of Cu-phytotoxicity. The outcome of the discussion may provide important clues for future research on NO-mediated mitigation of Cu-phytotoxicity.

Hydrogen peroxide potentiates defense system in presence of sulfur to protect chloroplast damage and photosynthesis of wheat under drought stress

“…However, the effectiveness of H 2 O 2 combined with S has not been reported earlier. (Sade et al, 2011;Fatma et al, 2016;Sehar et al, 2019;Rather et al, 2020aRather et al, , 2020bAsgher et al, 2021 (Khan et al, 2014;Sun et al, 2016;Shan et al, 2018;Li et al, 2020;Asgher et al, 2021). Xu et al (2011) also showed the involvement of the enzymes of the ascorbateglutathine cycle in protection of Kentucky bluegrass to drought damage.…”

“…Drought stress increased ROS and ABA contents in plants (Liu et al ., 2019), but supplementation of H 2 O 2 and S decreased the oxidative stress by increasing the activity of antioxidant enzymes. It is evident from previous reports that various abiotic stress factors such as drought, salt, and heavy metal stress lead to an increase in the activity of antioxidant enzymes and a decrease of ROS (Sade et al ., 2011; Fatma et al ., 2016; Sehar et al ., 2019; Rather et al ., 2020a, 2020b; Asgher et al ., 2021). In the present study, our results also suggest that both H 2 O 2 and S coordinately participate in upregulating the activity of antioxidant enzymes to decrease lipid peroxidation observed as content of H 2 O 2 and TBARS in leaves under drought stress.…”

“…Plants exposed to drought stress exhibit oxidative and osmotic stresses, which serve as a common response to adapt to these stress factors (Golldack et al ., 2014). To quench the excess of ROS generated in cells, plants exhibit various enzymatic and non‐enzymatic antioxidants, increased the accumulation of osmoprotectants and compatible solutes, which help the plants to obtain oxidative homeostasis (Porcel et al ., 2003; Khan et al ., 2013; Sekmen et al ., 2014; Fatma et al ., 2016; Pedranzani et al ., 2016; Sehar et al ., 2019; Hussain et al ., 2020; Rather et al ., 2020a, 2020b; Asgher et al ., 2021). In addition to the natural defense mechanisms employed by the plants, which help them to withstand exposure of stress, exogenous supplementation of several bio‐regulators and mineral nutrients are employed to improve drought stress tolerance.…”

“…which help the plants to obtain oxidative homeostasis (Porcel et al, 2003;Khan et al, 2013;Sekmen et al, 2014;Fatma et al, 2016;Pedranzani et al, 2016;Sehar et al, 2019;Hussain et al, 2020;Rather et al, 2020aRather et al, , 2020bAsgher et al, 2021). In addition to the natural defense mechanisms employed by the plants, which help them to withstand exposure of stress, exogenous supplementation of several bio-regulators and mineral nutrients are employed to improve drought stress tolerance.…”

Integrated Assessment of Nickel Electroplating Industrial Wastewater Effluent as a Renewable Resource of Irrigation Water Using a Hydroponic Cultivation System

“…Similarly, buildup of heavy metals in the rooting medium would significantly retard plant growth; elicit perturbations in cellular metabolism; affect the uptake of potassium, calcium, and magnesium; and decrease the number of flowers, fruits, and crop yield. The most common toxicity symptoms in plants are necrosis, chlorosis, wilting, and disturbance of physiological processes, including photosynthesis, transport of photo-assimilates, mineral nutrition, and plant structure damage ( Kasprzak et al, 2003 ; Rather et al, 2020 ).…”