Under cadmium stress, silicon has a defensive effect on the morphology, physiology, and anatomy of pea (Pisum sativum L.) plants

Abstract

Soil pollution with cadmium (Cd) is a serious threat to plant growth and development. On the other hand, silicon (Si) can support plants to cope with Cd stress. However, the Cd stress mitigating impact of Si reduction in pea (Pisum sativum L.) is not known. The objective of this study is to see if and how Si can reduce Cd toxicity. To the end, a greenhouse pot experiment was performed twice during the 2018/2019 and 2019/2020 seasons to investigate the effect of Si on the growth, anatomy, and biochemistry of Cd stressed peas plants. Cd exposure increased the contents of Cd ions in the root and shoot of pea plants. Consequentially, Cd accumulation in pea tissue significantly reduced plant growth i.e., plant height, leaf area, and shoot and root dry weights. The effect of Cd was concentration-dependent, where at low concentration (50 mg/kg soil), the plant height was 94.33 and 97.33cm and at high concentration (100 mg/kg soil), it was 89.0 and 91.0 cm in the two seasons, respectively. This growth reduction can be explained by the decrease in plants’ photosynthesis, whereas plants exposed to Cd toxicity had lower chlorophyll levels. At the anatomy level, high Cd concentrations resulted in anatomical abnormalities such as an unusual vascular system, abnormal lignification in the pith parenchyma, and enlarged cortical cells. Moreover, all Cd concentrations resulted in a highly significant decrease in stomatal area and stomatal density (the number of stomata per mm2). In addition to growth inhibition, Cd-induced oxidative damage to pea plants as indicated by increased hydrogen peroxide (H2O2) and Malondialdehyde (MDA) levels. To reduce stress toxicity, plants treated with Cd at 50 and 100 (mg/kg) showed a significant increase in antioxidant capacity. Peroxidase (POD) enzyme activity was significantly increased by 41.26%, 28.64%, 77.05%, and 60.77% in both seasons, respectively. Si at 300 ppm under Cd (100 mg/kg) stress conductions considerably reduced (MDA) contents by 29.02% and 29.12%, in the two seasons, respectively. The findings pointed out that Si’s ability to protect pea against the oxidative stress caused by Cd toxicity.

Morphological, Biochemical and Quality Control Analysis of Peas Genotypes under Cadmium Toxicity at the Seedling Stage

“…[30] found reduced seedling weight when they [31] also reported decreased root and shoot dry weight in peas upon Cd application. In line with our findings, Cd also reduced the growth of other plant species [32][33][34][35]. In this regard, Cd stress inhibits root and stem cell growth by inhibiting cell elongation and cell division via an inhibition activity of the glycolysis pathway.…”

Remediation of Cadmium Stress in Strawberry Plants Using Humic Acid and Silicon Applications

“…Some studies have reported that humic acid and silicon improve plant growth, providing resistance against abiotic stress and reducing heavy metal stress [22,[55][56][57]. Kim et al [57] reported that silicon mitigated heavy metal stress by regulating endogenous phytohormones, silicon genes and P-type heavy metal ATPases.…”

“…Kim et al [57] reported that silicon mitigated heavy metal stress by regulating endogenous phytohormones, silicon genes and P-type heavy metal ATPases. El-Okkiah et al [56] stated that Cd stress in pea plants produced anatomical abnormalities, decreasing stomatal density. In addition, Cd stress induced oxidative damage in pea plants by increasing hydrogen peroxide (H 2 O 2 ) and lipid peroxidation levels.…”

“…In addition, Cd stress induced oxidative damage in pea plants by increasing hydrogen peroxide (H 2 O 2 ) and lipid peroxidation levels. Silicon application to these plants considerably reduced lipid peroxidation, protecting pea tissues against the oxidative stress caused by Cd toxicity [56]. Rostami et al [55] noted that silicon applications altered Cd translocation and physiological trials of Lallemantia royleana, increasing vegatative growth, producing healthier plants under Cd stress.…”

Application of Zinc Oxide Nanoparticles to Mitigate Cadmium Toxicity: Mechanisms and Future Prospects

“…Roots are the primary way of entry for Cd in plants, and different metal channels and transporters play a critical role in Cd uptake from roots to their transportation in aerial plant parts [ 11 ]. Cadmium toxicity in plants causes diverse changes ranging from disruption in cell division, plant growth, photosynthetic efficiency, chlorophyll synthesis, enzyme activity, and increase in oxidative stress [ 12 , 13 , 14 ]. Cd-induced oxidative stress also causes membrane damage, disturbs electron transport, and interferes with nucleic acids (DNA) and photosynthesis [ 15 , 16 ].…”