可降解螯合剂对镉胁迫下籽粒苋根系形态及生理生化特征的影响

采用盆栽试验研究了可降解螯合剂EDDS和NTA对镉胁迫下籽粒苋(Amaranthus hybridus L.)根系形态及生理生化特征的影响。结果表明:当螯合剂施入10 mg/kg的镉污染土壤后,籽粒苋根系生物量和总长等根系形态指标与对照无显著差异,过氧化物酶(POD)、过氧化氢酶(CAT)活性、谷胱甘肽(GSH)和可溶性蛋白含量显著上升。当螯合剂施入100 mg/kg的镉污染土壤后,籽粒苋根系生物量、总长、表面积、体积及侧根数比对照显著减少了12.30%—23.98%、17.01%—24.90%、41.87%—57.93%、16.46%—32.94%和23.48%—53.35%;EDDS的施入使籽粒苋根系POD、CAT活性、GSH和可溶性蛋白含量显著升高;而NTA施入后,根系中的POD活性比对照降低了4.12%—35.95%,并且CAT活性和可溶性蛋白含量在2 mmol/kg NTA处理下分别显著降低了14.66%—15.79%和26.81%—30.48%;EDDS和NTA施入后,GSH含量比对照显著升高了14.73%—65.65%和28.05%—84.10%。当镉处理浓度分别为10 mg/kg和100 mg/kg时,螯合剂的施入显著增强了籽粒苋根系对镉的吸收,比对照分别增加了40.76%—103.10%和15.03%—49.49%。因此,EDDS和NTA施入镉污染土壤后,通过影响籽粒苋根系形态和生理生化过程以响应重金属镉的胁迫。

Effects of biodegradable chelants on the root morphology and physiological-biochemical characteristics of Amaranthus hybridus L. in cadmium contaminated soils

Heavy metal pollution in soil is a compelling global problem. Particularly, cadmium as a non-essential element negatively affects human health by way of food chain, even at low concentrations. In recent years, Cd concentrations in soils have dramatically increased with the development of industrial and agricultural and rural urbanization. Therefore, cleanup of Cd contaminated soils is emergent and imperative. Phytoremediation of heavy metal-contaminated soils has received increasing attention for its environmental benefits. However, phytoremediation efficiency was largely restricted by the bioavailability of heavy metal. Therefore, chelant-assisted phytoextraction has been proposed an alternative. In the phytoextraction process, roots contact with the toxic metal irons and plants usually adapt to the environment stress by changing their root morphology, and thus directly affect the physiological metabolic activity of the roots. However, there was little information dealing with the toxicity and mechanisms behind Cd tolerance concerning the roots under the chelant treatments. The objectives of the present study were to investigate the effects of biodegradable chelants on the root morphology and physiological-biochemical responses of hybridus L. root to cadmium stress. The soils in pot experiments were contaminated artificially with the Cd concentrations of 10 and 100 mg/kg soil, respectively. 0.52 g nitrogen, 0.40 g phosphorus (P₂O₅) and 0.36 g potassium (K₂O) were applied in every pot as a base fertilizer. After the soils were incubated for 4 weeks, four uniform A.hybridus seedlings (5-6 cm high with 3-4 fronds) were transplanted into each pot. Four replicates were run for each treatment and the experiment was arranged in a completely randomized design. Chelants assisted phytoextraction, EDDS and NTA, were added on the 65th and 75th day of transplanting at a concentration of 0 (Control), 1 and 2 mmol/kg. Finally, plant samples for evaluating root morphology, root biomass, the activities of peroxidase (POD), catalase (CAT), glutathione (GSH) concentration and soluble protein content (SP) were determined at the mature stages (90 days after transplanting). The results showed that under the treatments of EDDS and NTA, no significant differences were observed for the root biomass, root length, root surface area, root volume and lateral roots of A.hybridus in 10 mg/kg Cd contaminated soil. Moreover, chelant addition significantly increased the POD and CAT activities, glutathione (GSH) concentration and soluble protein content in roots of A.hybridus in 10 mg/kg Cd contaminated soil. When EDDS and NTA were applied to the 100 mg/kg Cd contaminated soil, root biomass, root length, root surface area, root volume and lateral roots of A.hybridus decreased by 12.30%-23.98%, 17.01%-24.90%, 41.87%-57.93%, 16.46%-32.94% and 23.48%-3.35%, and EDDS addition significantly improved the POD and CAT activities, GSH concentration and soluble protein content in roots. However, under the application of NTA, POD activities in roots were decreased by 4.12%-35.95%, and CAT activities and soluble protein content in roots significantly decreased by 14.66%-15.79% and 26.81%-30.48% compared to the control, respectively after the addition of 2 mmol/kg NTA. Moreover, under the addition of EDDS and NTA, GSH concentration increased by 14.73%-65.65% and 28.05%-84.10%, respectively. When the Cd concentrations were 10 and 100 mg/kg, the application of chelants significantly enhanced the Cd concentrations in roots of A.hybridus by 40.76%-103.10% and 15.03%-49.49%, respectively. In conclusion, the application of biodegradable EDDS and NTA in Cd contaminated soils could influence the root morphology and physiological-biochemical characteristics to resist the increased Cd concentrations.