Electrical properties of plant root cell plasma membrane influence the alleviation of Al and Cu phytotoxicity by Ca and Mg cations

• Published in: Environmental science and pollution research international Vol. 28; no. 35; pp. 48022 - 48037
• Main Authors: Li, Zhigen, Hu, Baowei
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 01.09.2021; Springer Nature B.V
• Subjects: Aluminum; Aquatic Pollution; Atmospheric Protection/Air Quality Control/Air Pollution; Calcium; Cations; Contaminants; Copper; Cowpeas; Earth and Environmental Science; Ecotoxicology; Electrical properties; Elongation; Environment; Environmental Chemistry; Environmental Health; Environmental science; Flowers & plants; Glycine max; Magnesium; Membranes; Nutrient solutions; Phytotoxicity; plant root cells; Plant roots; Plant species; plasma membrane; pollution; Regression analysis; Regression models; Research Article; root growth; roots; Soybeans; toxic substances; Toxicants; Toxicity; Trace metals; Triticum; uncertainty; Vigna unguiculata; Waste Water Technology; Water Management; Water Pollution Control; Wheat; Magnesium; Soybean; Calcium; Wheat; Metal toxicity
• ISSN: 0944-1344; 1614-7499; 1614-7499
• DOI: 10.1007/s11356-021-14001-6

Although it is known that cations such as calcium (Ca) and magnesium (Mg) can alleviate metal toxicity in plants, much uncertainty remains regarding the mechanisms by which this alleviation occurs. In this study, three plant species, cowpea ( Vigna unguiculata. cv. White Caloona), soybean ( Glycine max . cv. Bunya), and wheat ( Triticum . cv. Axe), were used to examine growth in nutrient solutions containing a series of cations (Ca and Mg) and toxicants (Al and Cu). The addition of Ca and Mg increased Al 3+ activities that induced 50% plant root elongation rate decline (EC 50 ) from 4.0, 4.2, 0.34 to 31, 22, 9.4 for cowpea, soybean, wheat respectively. However, when expressed as the Al 3+ activity at the root-cell plasma membrane (PM) surface, the addition of Ca and Mg increased Al sensitivity. In regression models, plant root elongation rate (RER) had higher R 2 values with Al 3+ activity at the PM than with Al 3+ activity in the bulk solutions (0.60, 0.58, 0.93 for cowpea, soybean, wheat respectively). For Cu, the addition of Ca and Mg alleviated its phytotoxicity when expressed as the Cu 2+ activity in the bulk-phase solutions for both cowpea and wheat. However, in soybean, the addition of Mg did not alter Cu toxicity when expressed as the Cu 2+ bulk activity. Generally, the metal activity at the outer PM surface of the root cells is a better predictor for their phytotoxicity than the activity in bulk solution ( R 2 =0.80, 0.80, 0.87 for cowpea, soybean, wheat respectively). These results supported the concept that the strength of alleviation of Ca and Mg cations depends on both the plant species and the toxicants that they alleviate. The different mechanisms should be fully considered in relevant assessments of trace metal toxicity in plants.