铅(Pb2+)和镉(Cd2+)对火炬树种子萌发及幼苗生长的影响

【目的】研究不同浓度重金属铅(Pb^2+)和镉(Cd^2+)对火炬树Rhus typhina种子萌发及幼苗生长的影响,探索火炬树对重金属铅、镉胁迫的耐受程度及机理。【方法】采用培养皿滤纸发芽法,分别用不同浓度Pb^2+(300、600、900、1200、1500 mmol/L)、Cd^2+(140、280、420、560、700 mmol/L)溶液处理火炬树种子,测定种子发芽率、发芽指数、幼苗胚根长和茎长、硫代巴比妥酸(TBARS)含量、可溶性蛋白含量、超氧化物歧化酶(SOD)活性及过氧化物酶(POD)活性。【结果】与对照相比,不同浓度Pb^2+、Cd^2+均对火炬树种子的发芽率、发芽指数和幼苗生长有抑制作用,但低浓度Pb^2+可促进根长和芽长的伸长。随着Pb^2+和Cd^2+溶液浓度的增加,幼苗叶片中SOD活性和可溶性蛋白含量表现为先增加后降低,POD活性和TBARS含量均逐渐升高。其中,Cd^2+浓度为700 mmol/L时,发芽率、发芽指数、芽长和SOD活性达到最低值,而TBARS含量最高;Pb^2+浓度为1500 mmol/L时,根长达到最低值,POD活性达到最高值;Pb^2+浓度为600 mmol/L时,可溶性蛋白含量最高。【结论】Pb^2+浓度为300 mmol/L时会抑制火炬树种子萌发,但会促进幼苗生长,其余浓度Pb^2+、Cd^2+胁迫下,火炬树种子与幼苗受到一定影响,但是均较好完成了萌发与幼苗生长,并表现出多种积极的适应性特征,未出现无根苗现象,火炬树较其他木本植物对铅、镉2种重金属表现出更强的耐性。本试验结果可为今后选用火炬树作为重金属污染土壤的植物修复材料提供理论参考。

Effects of Pb2+ and Cd2+ on seed germination and seedling growth of Rhus typhina

【Objective】To explore the resistance and physiological mechanism of Pb^2+and Cd^2+tress to Rhus typhina,the response of physiological characteristics and the growth indicators under Pb^2+and Cd^2+tress in R.typhina were investigated.【Method】Seeds of R.typhina were treated with Pb^2+(300,600,900,1200,1500 mmol/L)and Cd^2+(140,280,420,560,700 mmol/L solutions by using Petri dish and filter paper germination method.【Result】Then the germination indexes,morphological indexes and physicochemical properties were measured.Pb^2+and Cd^2+can inhibit the seed germination and seedling growth significantly,but the low concentration of Pb^2+can promote the root growth and shoot growth.With the increase of Pb^2+and Cd^2+concentration,peroxidase(POD)and the contents of thiobarbituric acid reactive substance(TBARS)increased;superoxide dismutase(SOD)and the contents of soluble protein increased firstly and then decreased.The germination rate,germination index,shoot growth and SOD decreased significantly when treated with 700 mmol/L Cd^2+,but there was a significant increase in TBARS.When the concentration of Pb^2+was 1500 mmol/L,root growth met a minimum level and POD met a maximum level;the contents of soluble protein was the maximum at 600 mmol/L.【Conclusion】The low concentration of Pb^2+can restrain the seed germination,but it can promote seedling growth.Although there were some changes of seed germination,seedling growth and physiological index under the stress of Cd^2+and high concentration of Pb^2+,R.typhina could complete germination and seedling growth,and showed a variety of positive adaptive characteristics.R.typhina is more tolerant than other woody plants in Pb^2+and Cd^2+,thus the results of this experiment can be used as a reference for selecting it as the phytoremediation species in the future.