镉胁迫对忍冬根系形态与根系分泌物的影响

Effects of Cadmium Stress on Root Morphology and Root Exudates of Lonicera japonica

本试验选择忍冬扦插苗为材料,设置0、5、10、25、50 mg·L^(-1)共5个镉(Cd)浓度梯度,采用盆栽砂培方式研究不同浓度镉胁迫对忍冬根系形态、根系分泌物pH值及根系分泌物中低分子量有机酸、可溶性糖含量的影响。结果表明,低浓度镉胁迫促进忍冬根系生长,其根系总长、表面积、体积在镉浓度为10 mg·L^(-1)时达到最大值,高浓度下根系生长则受到一定的抑制。根系分泌物的pH值随镉浓度增加无显著变化;低浓度镉胁迫对根系分泌物中可溶性糖含量无显著影响,高浓度镉胁迫则使可溶性糖含量显著减少。根系分泌物中,7种低分子量有机酸中有5种的含量及有机酸总量均随镉浓度增加而呈下降趋势,只有苹果酸和琥珀酸含量呈现先升后降趋势;低浓度镉胁迫下,忍冬根系分泌的有机酸以酒石酸为主,高浓度下则以苹果酸为主。综上,忍冬根系可以通过改变根系形态、调整根系分泌物种类及其分泌量等方式响应镉胁迫。

In this experiment,the cuttings of Lonicera japonica were selected as materials,and five dif-ferent concentrations of Cd(0,5,10,25,50 mgL^(-1))were utilized to investigate the effects of Cd stress on root morphology,and the pH value and levels of low molecular weight organic acids and soluble sugars in the root exudates of L.japonica through potting sand culture.The results showed that low concentration of Cd stress promoted the root growth of L.japonica,and the total length,surface area and volume of the root reached the maximum value when the Cd concentration was 10 mgL^(-1),higher concentrations of Cd inhibited root growth to some extent.The pH value of root exudates did not change significantly with the increase of Cd concentra-tion.Low concentration of Cd stress had no significant effect on soluble sugar content in root exudates,while high concentration of Cd stress significantly reduced soluble sugar content.Regarding the composition of root exudates,the contents of 5 out of 7 low molecular weight organic acids and the total content of organic acids decreased with the increase of Cd concentration,while the contents of malic acid and succinic acid increased firstly and then decreased.Under low Cd stress,tartaric acid was the main organic acid secreted by the roots of L.japonica,while under high Cd concentration stress,malic acid dominated.In conclusion,the root system of L.japonica could adapt to Cd stress by modifying root morphology,adjusting the composition and quantities of root exudates.