Photosynthesis performance, antioxidant enzymes, and ultrastructural analyses of rice seedlings under chromium stress

Abstract

The present study was conducted to examine the effects of increasing concentrations of chromium (Cr(6+)) (0, 25, 50, 100, and 200 μmol) on rice (Oryza sativa L.) morphological traits, photosynthesis performance, and the activities of antioxidative enzymes. In addition, the ultrastructure of chloroplasts in the leaves of hydroponically cultivated rice (O. sativa L.) seedlings was analyzed. Plant fresh and dry weights, height, root length, and photosynthetic pigments were decreased by Cr-induced toxicity (200 μM), and the growth of rice seedlings was starkly inhibited compared with that of the control. In addition, the decreased maximum quantum yield of primary photochemistry (Fv/Fm) might be ascribed to the decreased the number of active photosystem II reaction centers. These results were confirmed by inhibited photophosphorylation, reduced ATP content and its coupling factor Ca(2+)-ATPase, and decreased Mg(2+)-ATPase activities. Furthermore, overtly increased activities of antioxidative enzymes were observed under Cr(6+) toxicity. Malondialdehyde and the generation rates of superoxide (O2̄) also increased with Cr(6+) concentration, while hydrogen peroxide content first increased at a low Cr(6+) concentration of 25 μM and then decreased. Moreover, transmission electron microscopy showed that Cr(6+) exposure resulted in significant chloroplast damage. Taken together, these findings indicate that high Cr(6+)concentrations stimulate the production of toxic reactive oxygen species and promote lipid peroxidation in plants, causing severe damage to cell membranes, degradation of photosynthetic pigments, and inhibition of photosynthesis.

Chromium Bioaccumulation and Its Impacts on Plants: An Overview

“…Increased SOD and CAT activities Tang et al [26] Capsicum annuum Increased carotenoid content Oliveira [27] Chamomilla recutita Increased MDA level Kováčik et al [28] Echinochloa colona Increased CAT and POD activities Samantaray et al [29] Kandelia candel Increased MDA content, and activities of CAT and SOD Rahman et al [30] Ocimum tenuiflorum Increased proline level Rai et al [31] Oryza sativa Increased POD activity Ma et al [32] Table 1. Cont.…”

Chromium-Induced Reactive Oxygen Species Accumulation by Altering the Enzymatic Antioxidant System and Associated Cytotoxic, Genotoxic, Ultrastructural, and Photosynthetic Changes in Plants

“…Various heavy metals that influence plant biochemical, physiological, and metabolic processes affect photosynthesis and photosynthetic apparatus, leading to reduced plant growth and yield [3,8,19,23]. The effect of Cr on the photosynthesis and photosynthetic apparatus has been greatly studied in different plant species, and it mainly influences the enzymatic activities, electron transport chain, CO 2 fixation, photosynthetic phosphorylation, and structure of plastids [35,65,146,147]. In various plant species Cr-reduced chlorophyll contents, carotenoids, and photosynthetic activities have been greatly investigated, as summarized in Table 6.…”

Chromium (III) and its effects on soil microbial activities and phytoremediation potentials of Arachis hypogea and Vigna unguiculata

“…Chromium is a toxic non-essential metal for microorganisms and plants. In plants, it reduces productivity by the imposition of chronic diseases, loss of chlorophyll and protein contents (Ma et al, 2016). Hexavalent chromium (Cr 6+ ) is more toxic than trivalent chromium (Cr 3+ ) (Saha et al, 2011).…”