铬处理下超富集植物李氏禾根际溶解氧时空分布特征

Spatio-temporal Characteristics of O_(2)in Rhizosphere of Hyperaccumulator Leersia hexandra Swartz Under Chromium Stress

基于平面光极原位高分辨技术,在3个铬含量水平(0、50、100mg/kg)下研究了铬超富集植物李氏禾根际溶解氧的时空分布特征。结果表明:李氏禾根际土壤中溶解氧浓度较高的热区集中于根系周围区域,在根尖位置溶解氧浓度较高;根际溶解氧含量显著高于非根际土壤,且距离根部越远溶解氧平均含量越低,其中100 mg/kg铬处理李氏禾根部中心位置土壤溶解氧浓度为距离中心位置5 mm处的1.45倍;在8 d的拍摄周期中,对照处理根部中心位置溶解氧浓度最高达77.2%,显著高于50 mg/kg铬处理的50.2%和100mg/kg铬处理的42.3%。此外,3个铬含量水平下李氏禾根际溶解氧浓度都呈现先升高后降低的规律,第4天达到最高值。铬处理下李氏禾根际溶解氧浓度明显下降,这可能是李氏禾为避免根际富氧环境将Cr(Ⅲ)氧化为毒性更强Cr(Ⅵ)的保护性行为。

The spatio-temporal characteristics of O_(2)in the rhizosphere of Cr hyperaccumulator Leersia hexandra Swartz were studied using pot experiments with soils spiked with different levels(0,50,and 100 mg/kg)of Cr.The results show the hot spots of O_(2)are along entire root of L.hexandra,which are relatively higher at the root tips.O_(2)concentration in the rhizosphere is significantly higher than that in the bulk soil.For example,O_(2)concentration at the center of the root is 1.45 times higher than that 5 mm away from the root center.Besides,radial oxygen loss(ROL)becomes weaker when the distance from the root center becomes farther.During the experimental period of 8 days,O_(2)concentration at the root center of L.hexandra in the control group is 77.2%,which is significantly higher than that of 50 mg/kg Cr treatment group(50.2%)and 100 mg/kg Cr treatment group(42.3%).ROL is increased first and then decreased in all the 3 groups,which reaches the highest on the fourth day.ROL is significantly inhibited by the addition of Cr into the soil,which might be the protective behavior of L.hexandra to avoid the oxidation of Cr(Ⅲ)into more toxic Cr(Ⅵ).