Defense Mechanisms of Two Pioneer Submerged Plants during Their Optimal Performance Period in the Bioaccumulation of Lead: A Comparative Study

Abstract

Ceratophyllum demersum L. and Hydrilla verticillata (L.f.) Royle, two pioneer, submerged plants, effectively remove heavy metals from contaminated water. The present work evaluates the bioaccumulation and defense mechanisms of these plants in the accumulation of lead from contaminated water during their optimal performance period. C. demersum and H. verticillata were investigated after 14 days of exposure to various lead concentrations (5–80 μM). The lead accumulation in both C. demersum and H. verticillata increased with an increasing lead concentration, reaching maximum values of 2462.7 and 1792 mg kg−1 dw, respectively, at 80 μM. The biomass and protein content decreased significantly in C. demersum when exposed to lead. The biomass of H. verticillata exposed to lead had no significant difference from that of the controls, and the protein content increased for the 5–10 μM exposure groups. The malondialdehyde (MDA) content and superoxide dismutase (SOD), peroxidase (POD), and polyphenol oxidase (PPO) activities were much higher in C. demersum, suggesting considerable damage from lipid peroxidation and sensitivity to lead stress. Enzyme inhibition and inactivation were also observed in C. demersum at high lead concentrations (40–80 μM). The excellent growth status, low damage from lipid peroxidation, and high activity of catalase (CAT) and phenylalanine ammonia-lyase (PAL) observed in H. verticillata illustrate its better tolerance under the same lead stress.

Foliar spraying of indoleacetic acid (IAA) enhances the phytostabilization of Pb in naturally tolerant ryegrass by limiting the root-to-shoot transfer of Pb and improving plant growth

“…In the present study, low concentration of Pb induced an increase in anti-oxidase activity in the shoots and roots of ryegrass (with the highest activity recorded at 500 mg kg −1 soil Pb) and high Pb concentration decreased anti-oxidase activity ( Fig. 2 ), which was in accordance with the results of a previous study ( Li et al, 2018 ).…”

“…Oxidative stress is the most common toxic mechanism that hinders plant growth and colonization in metal-contaminated soils. In stressed environments, excessive reactive oxygen species (ROS) are generated and accumulate in plant tissue, resulting in irreversible oxidative damage to functional molecules like lipids, proteins, DNA and chloroplast pigments ( Chaki, Begara-Morales & Barroso, 2020 ; Gill & Tuteja, 2010 ; Li et al, 2018 ). Plant growth and development depend largely on the assimilates produced from photosynthesis, and the photosynthetic system is very vulnerable to Pb.…”

Zinc tolerant plant growth promoting bacteria alleviates phytotoxic effects of zinc on maize through zinc immobilization

“…Different plant growth parameters like average shoot length, root length, root number, leaf number, chlorophyll content of leaf number will be analyzed. The stress related enzymes viz., catalase (CAT), superoxide dismutase (SOD), peroxidase (POD), polyphenol oxidase (PPO) and phenylalanine ammonia lyase (PAL) will be studies in 14 days old seedlings as per the standard protocols previously published 51 . Analysis of Zn content in the maize plantlet was analyzed using atomic absorption spectroscopy (AAS).…”

Comparison of the Effects of Gradual and Acute Treatment with Mn on Physiological Responses of Rumex hydrolapathum Plants

“…Further, when the heavy metal concentration exceeds some threshold value for toxicity for the particular plant species, a decrease in peroxidase activity with a further increase in the metal concentration could show the negative consequences of the general metabolic stress situation associated with the breakdown of control systems and the inability to regulate the expression of defense genes [48]. However, it is often seen from the provided experimental results that peroxidase activity and MDA concentration increase nearly linearly in parallel with increased heavy metal concentration, often leading to more negative consequences for plant growth [49]. According to that logic, if an efficient enzymatic antioxidative system activity is induced, an increase in MDA concentration or any other indicator of membrane damage should not be observed.…”