title: Photosynthetic electron-transfer reactions in the gametophyte of Pteris multifida reveal the presence of allelopathic interference from the invasive plant species Bidens pilosa.
abstract: To date, the response of the fern gametophyte to its environment has received considerable attention. However, studies on the influence of plant invasion on the fern gametophyte are fewer. Allelopathy has been hypothesized to play an important role in biological invasion. Hence, it is necessary to study the allelopathy of invasive plant species to the fern gametophyte and elucidate the mechanisms by which invasive plants cause phytotoxicity. As one of the main invasive plants in China, Bidens pilosa exhibits allelopathic effects on the gametophytic growth of Pteris multifida. The root exudate plays an important role among various allelochemical delivery mechanisms in B. pilosa. The effect invasive plant species has on photosynthesis in native species is poorly understood. To elucidate this effect, the changes in photosynthesis in the gametophytes of P. multifida are analyzed to examine the mechanisms of the root exudates of B. pilosa. Meanwhile, a non-invasive plant, Coreopsis basalis, was also applied to investigate the effects on fluorescence and pigments in P. multifida gametophytes. We found that gametophytes exposed to both B. pilosa and C. basalis had decreased fluorescence parameters in comparison with the control, except for non-photochemical quenching. Furthermore, it was found that these parameters were markedly affected from day 2 to day 10 in the presence of both exudates at a concentration of 25% or above. B. pilosa exudate had a negative dose-dependent effect on chlorophyll a, chlorophyll b, carotenoid, and the total chlorophyll in the gametophyte. The inhibitory effects increased with increasing exudate concentrations of both species, exhibiting the greatest inhibition at day 10. In conclusion, B. pilosa irreversibly affected the photosynthesis of P. multifida on both PS I and PS II. Root exudates caused the primary damage with respect to the decrease of the acceptors and donors of photon and electron in photosynthetic units and the production and the relative yield of photochemical quantum in PS II. With the effects of exudates, part of the energy is released as heat in chloroplasts. The comparison of invasive and non-invasive plants in allelopathic experiments demonstrated that invasive plants were responsible for the critical damage to the photosynthetic process in local species.
authors.affiliation: Co-Innovation Center for Sustainable Forestry in Southern China, Nanjing Forestry University, Nanjing, Jiangsu 210037, China; College of Biology and the Environment, Nanjing Forestry University, Nanjing, Jiangsu 210037, China; Department of Botany, Smithsonian Institution, Washington, DC 20013, USA.
authors.forename: Kai-Mei
authors.initials: KM
authors.lastname: Zhang
authors.affiliation: College of Resources and Environmental Sciences, Nanjing Agricultural University, Nanjing, Jiangsu 210095, China; College of Biology and the Environment, Nanjing Forestry University, Nanjing, Jiangsu 210037, China.
authors.forename: Yu
authors.initials: Y
authors.lastname: Shen
authors.affiliation: Environmental Futures Research Institute, Griffith University, Nathan, Brisbane 4111, Australia.
authors.forename: Xiao-Qi
authors.initials: XQ
authors.lastname: Zhou
authors.affiliation: Co-Innovation Center for Sustainable Forestry in Southern China, Nanjing Forestry University, Nanjing, Jiangsu 210037, China; College of Biology and the Environment, Nanjing Forestry University, Nanjing, Jiangsu 210037, China. Electronic address: jwu4@njfu.edu.cn.
authors.forename: Yan-Ming
authors.initials: YM
authors.lastname: Fang
authors.affiliation: Co-Innovation Center for Sustainable Forestry in Southern China, Nanjing Forestry University, Nanjing, Jiangsu 210037, China; College of Biology and the Environment, Nanjing Forestry University, Nanjing, Jiangsu 210037, China.
authors.forename: Ying
authors.initials: Y
authors.lastname: Liu
authors.affiliation: State Key Laboratory of Pollution Control and Resource Reuse, School of the Environment, Nanjing University, Nanjing, Jiangsu 210046, China; Soil and Water Science Department, University of Florida, Gainesville, FL 32611, USA.
authors.forename: Lena Q
authors.initials: LQ
authors.lastname: Ma
mesh_terms: D004579:Electron Transport; D055993:Germ Cells, Plant / Q000378:metabolism*; D058865:Introduced Species; D010788:Photosynthesis; D010860:Pigments, Biological / Q000378:metabolism; D032495:Pteris / Q000235:genetics / Q000378:metabolism*; D013050:Spectrometry, Fluorescence
chemical_list: D010860:Pigments, Biological
keywords: Allelopathy; Bidens pilosa; Coreopsis basalis; Gametophyte; Photosynthesis; Pteris multifida