College of Natural Resources and Environment, South China Agricultural University, Guangzhou 510642, China.
College of Forestry, South China Agricultural University, Guangzhou 510642, China.
J Environ Sci (China). 2013 Sep 1;25(9):1890-6. doi: 10.1016/s1001-0742(12)60213-7.
Previous soil pot and field experiments demonstrated that co-cropping the hyperaccumulator Sedum alfredii with maize increased Zn phytoextraction by S. alfredii and decreased Zn uptake by maize shoots. This hydroponic experiment was conducted to investigate whether the facilitation of Zn phytoextraction by S. alfredii resulted from improved dissolution in this co-cropping system and its relation to root exudates. S. alfredii and maize were mono- and co-cropped (without a root barrier) in nutrient solution spiked with four Zn compounds, ZnS, ZnO, Zn3(PO4)2 and 5ZnO x 2CO3-4H2O (represented as ZnCO3) at 1000 mg/L Zn for 15 days without renewal of nutrient solution after pre-culture. The root exudates were collected under incomplete sterilization and analyzed. The results indicated that the difference in Zn salts had a greater influence on the Zn concentration in maize than for S. alfredii, varying from 210-2603 mg/kg for maize shoots and 6445-12476 mg/kg for S. alfredii in the same order: ZnCO3 > ZnO > Zn3(PO4)2 > ZnS. For the four kinds of Zn sources in this experiment, co-cropping with maize did not improve Zn phytoextraction by S. alfredii. In most cases, compared to co-cropped and mono-cropped maize, mono-cropped S. alfredii resulted in the highest Zn2+ concentration in the remaining nutrient solution, and also had a higher total concentration of low molecular weight organic acids (LMWOA) and lower pH of root exudation. Root exudates did partly influence Zn hyperaccumulation in S. alfredii.
先前的土培和田间试验表明，与玉米间作超积累植物东南景天会增加东南景天对锌的植物提取量，同时降低玉米地上部分对锌的吸收。本水培试验旨在研究东南景天对锌的植物提取的促进作用是否源于该间作系统中锌的溶解增强，以及这种增强作用与根系分泌物的关系。在含有四种锌化合物（硫化锌、氧化锌、磷酸锌和 5ZnO x 2CO3-4H2O[代表 ZnCO3]）的营养液中，分别对东南景天和玉米进行单作和间作（没有根障），锌浓度为 1000mg/L，预培养后 15 天不更换营养液。在不完全灭菌的条件下收集根系分泌物并进行分析。结果表明，锌盐种类的差异对玉米中锌浓度的影响大于对东南景天的影响，玉米地上部分的锌浓度变化范围为 210-2603mg/kg，东南景天的锌浓度变化范围为 6445-12476mg/kg，按此顺序依次为：ZnCO3＞ZnO＞Zn3(PO4)2＞ZnS。对于本实验中的四种锌源，与玉米间作并没有提高东南景天对锌的植物提取量。在大多数情况下，与间作和单作玉米相比，单作东南景天会导致剩余营养液中的 Zn2+浓度最高，同时具有较高浓度的低分子量有机酸（LMWOA）和较低的根分泌物 pH 值。根系分泌物在一定程度上影响了东南景天对锌的超积累。
