title: Two types of kinetics of membrane potential of water plant leaves illuminated by ultraviolet light.
abstract: The effects of ultraviolet-B (UV-B) radiation on plasma membrane of water plant (Elodea canadensis, Vallisneria spiralis) cells were investigated by using microelectrode methods. A fast and reversible depolarization of membrane potential occurs initially during exposure of leaf cells to UV on a white light background, after which a slow phase of depolarization sets in. On action series, UV is pulsed for 15 s, with dark interval of 3 min, no monotonous response of systems on the UV excitation is observed. The action spectrum of the fast UV response lies in the interval of 300-330 nm and that of the slow phase-in the interval of 280-300 nm. The input impedance of membranes remains unchanged during the period of exposure. It is concluded that the H(+)-extruding complex of plant cell plasma membranes really consists of two types of interrelated electronic H(+)-pumps: an H(+)-pump of redox-active nature and the H(+)-pump of the H(+)-ATPase enzyme complex. Clearly, during the exposure of leaf cells to UV light, initially, the H(+)-pump of redox-active nature and then H(+)-ATPase are inhibited. It is proposed that the initial chromophore of UV-B light on plasma membrane can be one of the components of H(+)-pump of redox-active nature. It is probably the molecular of quinone.
authors.affiliation: Department of Biophysics and Molecular Biology, Baku State University, 370143 Baku, Azerbaijan.
authors.forename: R I
authors.initials: RI
authors.lastname: Khalilov
authors.forename: I S
authors.initials: IS
authors.lastname: Ahmadov
authors.forename: S G
authors.initials: SG
authors.lastname: Kadirov
mesh_terms: D017097:Electric Impedance; D031321:Hydrocharitaceae / Q000502:physiology / Q000528:radiation effects*; D007700:Kinetics; D008564:Membrane Potentials / Q000502:physiology / Q000528:radiation effects*; D008839:Microelectrodes; D018515:Plant Leaves / Q000502:physiology / Q000528:radiation effects; D014466:Ultraviolet Rays