title: Endophytic infection alleviates Pb(2+) stress effects on photosystem II functioning of Oryza sativa leaves.
abstract: The aims of this study were to examine the effect of Pb(2+) stress on the primary reaction of photosynthesis and to assess the potential benefits of endophytic infection on the Pb(2+) tolerance of rice seedlings. Rice inoculated with an endophytic fungus (E+) and non-inoculated (E-) were subjected to 0, 50, 100, 150 and 200 μM Pb(2+). The responses to Pb(2+) stress were characterized by the analysis of Chl a fluorescence. A comparison of E- with E+ rice seedlings, as evaluated by their performance index (PI(ABS) and PI(tot)), revealed the inhibitory effects of Pb(2+) on photosystem II (PSII) connectivity, the oxygen evolving complex (OEC), and on the J step of the induction curves, which is associated with an inhibition of electron transport from the quinone acceptor Q(A) to Q(B). Furthermore, the changes of the donor and the acceptor parameters of PSII were greater in E- than in E+ under Pb(2+) stress. These observations suggest that the efficiency and stability of PSII are markedly affected by Pb(2+) stress, and the photosynthetic energy conservation in E+ was more effective than in E-. We showed that endophytic infection plays an important role in enhancing the photosynthetic mechanism of rice seedlings exposed to Pb(2+) stress.
authors.affiliation: College of Chemistry and Life Science, Shenyang Normal University, Shenyang 110034, PR China. Electronic address: lxmls132@163.com.
authors.forename: Xuemei
authors.initials: X
authors.lastname: Li
authors.affiliation: Environmental Science Department of Liaoning University,Shenyang 110036, PR China. Electronic address: lihongzhang132@163.com.
authors.forename: Lihong
authors.initials: L
authors.lastname: Zhang
mesh_terms: D002734:Chlorophyll / Q000502:physiology; D060026:Endophytes / Q000502:physiology*; D007854:Lead / Q000633:toxicity*; D012275:Oryza / Q000187:drug effects* / Q000378:metabolism / Q000382:microbiology; D010788:Photosynthesis / Q000187:drug effects*; D045332:Photosystem II Protein Complex / Q000378:metabolism; D018515:Plant Leaves / Q000187:drug effects / Q000378:metabolism / Q000382:microbiology; D013312:Stress, Physiological
chemical_list: D045332:Photosystem II Protein Complex; D002734:Chlorophyll; D007854:Lead
keywords: Chlorophyll fluorescence; Endophytic infection; Pb(2+) stress; Photosystem II