中文摘要：

通过研究土壤菲胁迫对高丹草（Sorghum bicolor×S.sudanense）幼苗生长及叶绿素荧光特性以及光能分配参数的影响,探讨了土壤菲胁迫下高丹草幼苗的光保护机制.结果表明：低于50 mg·kg-1的土壤菲浓度对高丹草幼苗生长及光合作用的抑制作用较小,当浓度大于50 mg· kg-1时,幼苗生长随着菲浓度的增加受到明显抑制,且对地下部的抑制作用大于地上部.幼苗叶片叶绿素含量随土壤菲浓度增加而降低,且叶绿素a相对于叶绿素b对土壤菲胁迫更敏感.土壤菲胁迫降低了PSⅡ反应中心活性和电子传递能力,导致其光能利用能力降低,特别是对高光强的利用能力下降.最大光化学效率（Fv/Fm）的变化幅度较小,即幼苗叶片未发生明显的光抑制现象.土壤菲胁迫明显改变了高丹草幼苗叶片PSⅡ反应中心光能分配参数,用于光化学反应的量子产额（YPSⅡ）降低,而依赖于类囊体膜两侧质子梯度叶黄素循环的量子产额（YNPQ）增加,即幼苗叶片启动了依赖于叶黄素循环的非辐射能量耗散机制来保护PSⅡ的正常生理功能,降低光合电子传递链上的压力,另外失活PSⅡ反应中心的热耗散量子产额（YNF）仅在土壤菲浓度达300 mg· kg-1时有小幅增加,说明土壤菲胁迫仅仅造成PSⅡ反应中心活性的降低,并未使PSⅡ反应中心大量失活.

英文摘要：

In this paper,Sorghum bicolor× S.sudanense was taken as an experimental material,the seedlings growth,chlorophyll fluorescence characteristic and light distribution parameters were studied to investigate the protection mechanism of Sorghum bicolor× S.sudanense seedling under the soils of phenanthrene （Phe） stress.The results showed that the growth and photosynthesis of the seedlings were lightly inhibited when the Phe concentration of soils was less than 50 mg · kg-1,namely Sorghum bicolor× S.sudanense seedling had certain toleration to the soils of Phe stress.When the Phe concentration of soils was more than 50 mg · kg-1,the growth of the seedlings was inhibited significantly.With the increasing of the soils Phe concentration,The inhibition effect of Phe stress on the growth of underground part was more serious than that of aboveground part.The chlorophyll contents of Sorghum bicolor× S.sudanense seedling decreased with the Phe concentration of soils increasing.Chlorophyll a was more sensitive than chlorophyll b under the soils of Phe stress.The electron transport rate （ETR） and photochemical quenching coefficient （qP） of Sorghum bicolor × S.sudanense decreased significantly under the soils of Phe stress,and actual photochemical efficiency of PS Ⅱ,ETR,qP and maximum ETR of light compensation also decreased at different illumination intensities.These results indicated that the activities of PS Ⅱ reaction center,the rate of photosynthetic electron transport and the capability of light use,especially the light usage capability of high intensity decreased under the soils of Phe stress.But the maximal photochemical efficiency of PSⅡ （Fv/Fm） had minor variations under the soils of Phe stress showing no significant photoinhibition in the leaves of Sorghum bicolor × S.sudanense seedlings.The light distribution parameters of Sorghum bicolor × S.sudanense leaves was changed significantly under the soils of Phe stress.The proportion of the quantum yield of PS Ⅱ photochemistry （YPSⅡ） d