Abstract
Metabolic responses to cadmium (Cd) may be associated with variations in Cd tolerance in plants. The objectives of this study were to examine changes in metabolic profiles in bermudagrass in response to Cd stress and to identify predominant metabolites associated with differential Cd tolerance using gas chromatography-mass spectrometry. Two genotypes of bermudagrass with contrasting Cd tolerance were exposed to 0 and 1.5 mM CdSO4 for 14 days in hydroponics. Physiological responses to Cd were evaluated by determining turf quality, growth rate, chlorophyll content and normalized relative transpiration. All these parameters exhibited higher tolerance in WB242 than in WB144. Cd treated WB144 transported more Cd to the shoot than in WB242. The metabolite analysis of leaf polar extracts revealed 39 Cd responsive metabolites in both genotypes, mainly consisting of amino acids, organic acids, sugars, fatty acids and others. A difference in the metabolic profiles was observed between the two bermudagrass genotypes exposed to Cd stress. Seven amino acids (norvaline, glycine, proline, serine, threonine, glutamic acid and gulonic acid), four organic acids (glyceric acid, oxoglutaric acid, citric acid and malic acid,) and three sugars (xylulose, galactose and talose) accumulated more in WB242 than WB144. However, compared to the control, WB144 accumulated higher quantities of sugars than WB242 in the Cd regime. The differential accumulation of these metabolites could be associated with the differential Cd tolerance in bermudagrass.
Highlights
Cadmium (Cd) is a vast environmental pollutant resulting primarily from anthropogenic activities including agriculture, mining, metallurgy and manufacturing [1, 2]
After samples were subjected to Cd stress for 7 or 14 d, turf quality was higher in WB242 than WB144 (Fig. 1A)
Cd stress resulted in a lower level of normalized relative transpiration (NRT) in the two bermudagrass genotypes during whole experimental period, to a higher reduction in WB144 than WB242 (Fig. 2)
Summary
Cadmium (Cd) is a vast environmental pollutant resulting primarily from anthropogenic activities including agriculture, mining, metallurgy and manufacturing [1, 2]. It is highly mobile, bio-accumulated in lower organisms and transferred to higher trophic levels in the food chain. Previous studies have shown that Cd could decrease carbon assimilation, generate oxidative stress, inhibit chlorophyll synthesis, reduce nutrient uptake, impair photosynthesis and inhibit plant growth [6,7,8,9,10]. Cd uptake and accumulation in plants initiates a series of morphological, physiological and biochemical changes
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