镉胁迫及施氮措施对喀斯特特有树种蚬木光合生理的影响

摘要

This paper studied the effects of nitrogen application on the growth and physiological characteristics of Excentrodendron hsienmu under Cd stress,an endemic plant species occurring in Karst area to provide scientific basis for the management of cadmium pollution and remediation measures.The results indicated that under the stress of high Cd concentration (120 mg · kg-1),seedling height (H),ground diameter (D),transpiration rate (Tr),net photosynthetic rate (Pn),and chlorophyll content decreased by 36.6％,66.4％,34.3％,20.9％,and 4.1％,respectively,while intercellular CO2 concentration (Ci) increased by 12.1％,and no significant changes in the stomatal conductance (Gs).Under low Cd concentration stress (30 mg · kg-1 · Cd2+) and the application of nitrogen,H,D,chlorophyll content,Pn and Tr increased slightly,and then decreased with the increase of applying nitrogen,while Ci decreased first,and then increased,and Gs decreased constantly.Under high level of applying nitrogen (0.9 g · kg 1),H,D,chlorophyll content,Pn,Tr,Ci,and Gs decreased by 9.7％,17.9％,23.9％,36.0％,13.5％,43.1％ and 5.6％,respectively,compared with those without nitrogen application.Under high Cd concentration,H,D,chlorophyll content,Pn,Gs and Tr decreased with the increase of nitrogen application and compared with those without nitrogen application,the parameters mentioned above decreased by 29.1％,23.4 ％,19.3 ％,40.3％,41.7％,and 17.9％,respectively,while Ci increased by 5.5％,indicating thatr non-stomatal limitation was the key factor that affected the photosynthesis of E.hsienmu under cadmium stress.The adaptation of E.hsienmu was promoted under low cadmium stress by adding low level nitrogen.E.hsienmu was intimidated under low cadmium stress by adding high nitrogen or under high cadmium stress by adding nitrogen.%采用盆栽方法,研究镉胁迫及施氮措施对喀斯特特有树种蚬木(Excentrodendron hsienmu)光合生理特性的影响,为镉污染的治理及修复措施提供科学依据.结果表明,镉胁迫显著抑制了蚬木苗高、地径、净光合速率(Pn)、蒸腾速率(Tr)和叶绿素含量,显著提高了蚬木胞间二氧化碳浓度(Ci),高镉(120 mg·kg-1·Cd2+)胁迫时,分另l比CK降低或升高了36.6％、66.4％、34.3％、20.9％、4.1％、12.1％;气孔导度则无明显变化.低镉(30 mg· kg-1·Cd2+)胁迫下施氮,蚬木苗高、地径、叶绿素含量、Pn及Tr随着施氮浓度的增加表现为先微弱上升后下降,而Ci正好相反表现为先降后增,Gs则表现为不断降低;高氮(0.8 g· kg-1)下,均比不施氮处理分别下降了9.7％、17.9％、23.9％、36.0％、13.5％、43.1％和5.6％.高镉胁迫下施氮,蚬木苗高、地径、叶绿素含量、Pn、Gs和Tr均随着施氮量的增加而不断降低,并且高氮均比不施氮显著降低了29.1％、23.4％、19.3％、40.3％、41.7％和17.9％;Ci则显著地提升5.5％.说明镉胁迫下影响蚬木光合作用的主要因素为非气孔因素.低镉胁迫下施低氮对蚬木镉胁迫环境的适应性有一定的提升作用,高镉下施氮以及低镉下施高氮均使氮协同镉对蚬木产生了胁迫作用.