Lead exposure dose-dependently affects oxidative stress, AsA-GSH, photosynthesis, and mineral content in pakchoi (Brassica chinensis L.)

Abstract

Lead (Pb) is a heavy metal pollutant and negatively affects agriculture and ecosystems. Pb can cause oxidative stress and abnormal plant growth. The ascorbic acid-glutathione (AsA-GSH) cycle mainly exists in chloroplasts and resists oxidative stress, scavenges reactive oxygen radicals, and maintains normal photosynthesis. However, the dosage related effects of Pb on pakchoi photosynthesis, via oxidative stress and the AsA-GSH system, remains unclear. In this study, various Pb dosage stress models were tested (low: 300 mg/kg; medium: 600 mg/kg; high: 900 mg/kg). Pb stress induced a dose-dependent increase in Pb content in pakchoi leaves (P < 0.05). Principal component analysis showed that Se, B, and Pb were significantly and negatively correlated. Pb stress also increased MDA content and decreased antioxidant enzymes SOD, GSH-Px, and T-AOC activities (P < 0.05). We also found that Vc content, as well as the GSH/GSSG ratio, decreased. Additionally, Pb stress destroyed chloroplast structure, decreased photosynthesis indicators Pn, Tr, Gs, Ci and VPD, and attenuated Fv/Fm and Fv/Fo (P < 0.05). In the high-dose group, the contents of chlorophyll a, chlorophyll b, and carotenoids decreased significantly, while the expression of chloroplast development genes (GLK, GLN2) decreased (P < 0.05). Our data suggest that Pb stress leads to dosage-dependent, aberrant photosynthesis by inhibiting the AsA-GSH system in pakchoi. This study expands the Pb toxicology research field and provides indications for screening antagonists.

Thymol Deploys Multiple Antioxidative Systems to Suppress ROS Accumulation in Chinese Cabbage Seedlings under Saline Stress

“…Then, the GSH content was measured with the DTNB method in sample extractions before and after adding GR, respectively. The GSSG content was calculated from the difference between two measurements [31,32]. The DHA content was determined by using the commercial kit BC1240 (Solarbio Life Science, Beijing, China).…”

Flavonoid metabolism plays an important role in response to Pb stress in maize at seedling stage

“…When plants are exposed to Pb stress, the development of roots and aerial parts is attenuated, especially in roots, probably due to increased Pb accumulation [18,19]. Previous studies have shown that the reasons for the retardation of seed germination and plant growth under Pb are as follows: inhibited enzyme activity [20], disruption of plant water status [21], disruption of nutrient uptake [22], photosynthesis inhibition [23], disruption of cell division [24], oxidative stress [25], and lipid peroxidation [26]. To survive in soils, plants adopt several mechanisms to mitigate Pb stress, including cell wall adsorption and obstruction [27], excretion of metal ions into extracellular spaces [28], cellular sequestration [28], an increase in nonenzymatic antioxidants [29], and an increase in metalbinding ligands [30].…”