Resistance of alfalfa and Indian mustard to Cd and the correlation of plant Cd uptake and soil Cd form

Abstract

Phytoremediation of heavy metal-contaminated soil is considered to be one ecological environmental protection way that is effective and economical. The selection of suitable hyperaccumulators is a key issue for phytoremediation of heavy metal-contaminated soil. Pot experiments were conducted to study the effects of different Cd levels (0, 75, 150, 300, and 600 mg kg Cd) on the dry weight, antioxidant enzyme activities, malondialdehyde (MDA) contents, Cd concentration, Cd accumulation, and soil Cd form distribution ratio (FDC) of alfalfa (Medicago sativa L.) and Indian mustard (Brassica juncea L.). The correlations between Cd concentration in shoots and roots of alfalfa and Indian mustard and soil Cd form were also investigated. The results showed that with the increase of soil Cd levels, dry weight of shoot and root of alfalfa and Indian mustard significantly decreased, which decreased by 50.0-71.8% and 29.6-59.3% (alfalfa), 59.6-89.0% and 64.3-74.8% (India mustard), respectively, compared with the control. With the increase of soil Cd level, superoxide dismutase (SOD) activity in shoot of alfalfa significantly increased. Catalase (CAT) activity and malondialdehyde contents in shoots and roots of alfalfa and Indian mustard, as well as superoxide dismutase activity in the roots of alfalfa and Indian mustard increased first and then decreased with the increase of soil Cd level. With increasing Cd stress, Cd concentration in shoots and roots of alfalfa and Indian mustard significantly increased. At soil Cd level of 75 mg kg, Cd concentrations in shoots of alfalfa and Indian mustard exceeded the critical value of Cd-hyperaccumulator (100 mg kg), which was 356.46 mg kg and 308.74 mg kg, respectively. Cadmium concentrations in shoots and roots of plants were in the order of that of alfalfa > Indian mustard; total Cd accumulation in the aboveground tissues and roots of the plants was in the order of that of Indian mustard > alfalfa at the same Cd level. With increasing soil Cd level, Cd concentrations of exchangeable form (EXC-Cd), carbonate-bound form (CAB-Cd), iron-manganese oxide-bound form (FeMn-Cd), organic-bound form (OM-Cd), and residual form (RES-Cd) showed an increasing trend. The form distribution ratio of soil Cd forms in alfalfa's rhizosphere was in the order of that of exchangeable form Cd > carbonate-bound form Cd > iron-manganese oxide-bound form Cd > residual form Cd > organic-bound form Cd. Except for organic-bound form Cd, soil Cd forms were significantly positively correlated with Cd concentration in shoot and root (P < 0.01). Comprehensively considering the biomass and Cd accumulation, Indian mustard is more suitable as remediation material for soil Cd pollution.

Inoculation of Bacillus megaterium strain A14 alleviates cadmium accumulation in peanut: effects and underlying mechanisms

“…Reduction of exchangeable Cd in rhizosphere soil after A14 inoculation may help improve agronomic traits of peanuts (Zhang et al 2019…”

Antioxidants enzyme activity in Brassica oleracea var. acephala under cadmium stress

“…(alfalfa), the SOD levels were increasing until the concentration of 150 mg/kg of Cd, after which the levels of that enzyme were dropping until the final concentration of 600 mg/kg [55]. For POX, the levels dropped until the concentration of 75 mg/kg of Cd.…”

Glomus mosseae improved the adaptability of alfalfa (Medicago sativa L.) to the coexistence of cadmium-polluted soils and elevated air temperature

“…Numerous studies indicate that cadmium (Cd) is high toxic, nonbiodegradable and widespread ( Haider et al., 2021 ; Wang et al., 2022a ), which poses a challenge for plant defense system. Low Cd level showed a stimulation on peroxidase (POD) and catalase (CAT) activities, chelators and osmolytes in alfalfa ( Zhang et al., 2019 ; Wang et al., 2021 ; Wang et al., 2022a ), however, POD and CAT activities in shoots decreased obviously with increasing Cd ( Zhang et al., 2019 ). Therefore, the response of defense system in alfalfa to Cd stress might be associated with the dose and exposure duration.…”