title: UV-B exposure enhances senescence of wheat leaves: Modulation by photosynthetically active radiation.
abstract: The alterations in structure and function of photosystem II (PS II) during the senescence of primary leaves of wheat seedlings have been compared with the changes induced by ultraviolet-B (UV-B) radiation in the presence or absence of photosynthetically active radiation (PAR). The results indicated that the senescence-induced loss in pigment content, thylakoid membrane integrity and carotenoid-to-chlorophyll (Car-to-Chl) energy transfer efficiency was intensified by exposure to UV-B radiation. Different parameters for the measurement of PS II activity, such as Chl a fluorescence, O2-evolution and thermoluminescence intensity, were altered during senescence and these alterations were furthered by UV-B irradiation. The damage of photosynthetic apparatus by UV-B exposure in the presence of PAR was less than the damage in absence of PAR. The activation of molecular defense mechanisms could be a factor in the alleviation of UV-B damage in the presence of PAR.
authors.affiliation: Anchal College, Padampur P O: Rajborasambar, 768036 Bargarh, Orissa, India.
authors.forename: M K
authors.initials: MK
authors.lastname: Pradhan
authors.forename: P N
authors.initials: PN
authors.lastname: Joshi
authors.forename: J S
authors.initials: JS
authors.lastname: Nair
authors.forename: N K
authors.initials: NK
authors.lastname: Ramaswamy
authors.forename: R K
authors.initials: RK
authors.lastname: Iyer
authors.forename: B
authors.initials: B
authors.lastname: Biswal
authors.forename: U C
authors.initials: UC
authors.lastname: Biswal
mesh_terms: D016922:Cellular Senescence / Q000502:physiology / Q000528:radiation effects*; D004307:Dose-Response Relationship, Radiation; D010100:Oxygen / Q000378:metabolism; D010788:Photosynthesis / Q000502:physiology* / Q000528:radiation effects; D045332:Photosystem II Protein Complex / Q000502:physiology / Q000528:radiation effects; D018515:Plant Leaves / Q000502:physiology* / Q000528:radiation effects*; D011829:Radiation Dosage; D014908:Triticum / Q000502:physiology* / Q000528:radiation effects*; D014466:Ultraviolet Rays
chemical_list: D045332:Photosystem II Protein Complex; D010100:Oxygen