秋茄(Kandelia candel)幼苗对菲和荧蒽污染的生理生态效应

Eco-physiological responses of Kandelia candel seedlings to phenanthrene(PHE) and fluoranthene(FLA) treatment

通过盆栽实验,研究了5种不同浓度的菲(1、5、10、50 m.gkg-1和100 m.gkg-1)和荧蒽(2、20、40、80 mg.kg-1和100mg.kg-1)对红树植物秋茄幼苗的生长量、叶片的叶绿素含量、光合作用和根系活力等生理生态指标的影响。结果表明:(1)随着PAHs浓度增加和处理时间延长,秋茄根受毒害越严重,表现为肿大、变黑、腐烂。(2)根系活力随着处理浓度的增加而增强,随着处理时间的延长呈先增加后降低的趋势。(3)PAHs浓度和处理时间对植株含水量和根冠比几乎无影响,却明显降低了红树幼苗的根、茎、叶重,因而总生长量较对照低,干物质积累量减少。(4)增加PAHs浓度和处理时间使叶气孔阻力增加,细胞间隙CO2浓度减少,叶绿素a、b的含量减少,从而降低了红树幼苗的净光合速率和蒸腾速率。如菲各浓度处理的第6周,幼苗叶片净光合速率与第3、9周的状况存在着显著性差异;而荧蒽各浓度处理的第6周,幼苗叶片净光合速率与第3周的状况不存在着显著性差异,到了第9周才对幼苗叶片净光合速率有明显影响。(5)菲浓度处理对秋茄幼苗生长及光合作用的影响大于荧蒽,说明荧蒽是一类更加稳定的化合物。总体来看,秋茄幼苗对不同类型PAHs有不同的耐受性。

The mangrove ecosystem,an important intertidal estuarine wetland along the coastlines of tropical and subtropical regions,is exposed to anthropogenic contamination by polycyclic aromatic hydrocarbons（PAHs） from oil spills,ship traffic,urban runoff,wastewater and industrial discharge, as well as atmospheric deposition of vehicle exhaust and industrial stack emission.However,the eco-physiological toxicity of PAHs contaminated sediment to mangrove is a nearly untouched area of research.This study was conducted to determine the effect of PAHs contaminated sandy soil on mangrove specie Kandelia candel.K.candel seedlings were cultured with phenanthrene（PHE） or fluoranthene（FLA） contaminated sandy soil for determining the eco-physiological responses of K.candel.The influence of increasing concentrations of PHE（0,1, 5,10,50 mg·kg^-1 and 100 mg·kg^-1） and FLA（0,2,20,40,80 mg·kg^-1 and 100 mg·kg^-1） on total biomass,chlorophyll content,photosynthesis and root activity were investigated.Results were as follows：（1） After 9 weeks of exposure to PAHs,the roots of K.candel appeared swelling,and then turned black and rotten.The toxicity to the root at high concentration of PAHs was higher than at low concentration of PAHs.The percentage of rotten roots of contaminated seedlings was higher than the control,which indicated that PAHs inhibited the root growth of K.candel.（2） With increasing concentrations of PAHs,the root activity of K.candel seedlings increased at first and then decreased with the prolonging of culture time.（3） With the prolonging of culture time,water content and the root to shoot ratio of K.candel seedling showed no significant difference from the control group at various concentrations of PHE and FLA.However,the root biomass and above-ground biomass of K.candel seedlings decreased significantly in comparison to the control,with an increase of PAHs concentration in the sandy soil.（4） The chlorophyll a,b contents in the leaves of K.candel decreased moderately with increase of PAHs concentration in the sandy soil.Moreover,decrease in stomatal conductance reduced the input of CO2,which may be one of the reasons for decreasing net photosynthetic rate of K.candel seedlings leaves.With the treatments of PHE at 6 weeks,the net photosynthetic rate of K.candel seedling leaves showed significant difference from 3 weeks′ treatment but not the treatments of FLA.There are significant differences between 9 weeks′ treatment and 3 weeks′ treatment for both PHE and FLA.With increasing concentrations of PHE and FLA,decrease in the transpiration rate of K.candel seedling was observed.（5） The study clearly demonstrated that the growth and physiological function of mangrove species K.candel was adversely impacted by PAHs contaminated sandy soil.The effects of PHE and FLA on the growth of K.candel seedling were similar.However,the toxic effect of PHE on K.candel was more serious than that of FLA.The tolerance of K.candel to PHE and FLA depended on different physical and chemical properties of the PAHs.