title: Inhibition of photosystems I and II activities in salt stress-exposed Fenugreek (Trigonella foenum graecum).
abstract: Fenugreek (Trigonella foenum graecum) seedlings were exposed to increasing NaCl concentrations in the growth medium to examine the effect of salt stress on the electron transport reactions of photosynthesis. Activities of both photosystem II (PSII), measured by chlorophyll fluorescence, and photosystem I (PSI), measured by P700 photooxidation, were decreased by salt stress. The inhibition proceeded in a two step manner. At the lower salt concentrations used and shorter exposition periods, electron transfer between the quinone acceptors of PSII, Q(A) and Q(B), was strongly retarded as shown by an increased amplitude of the OJ phase of the OJIP chlorophyll fluorescence induction traces and slowed chlorophyll fluorescence relaxation kinetics following a single turn-over flash. The above indicated a disturbance of the Q(B) binding site likely associated with the first step of photoinhibition. In the second step, strong photoinhibition was observed as manifested by increased F(0) values, declined F(v)/F(0) and loss of photoactive P700.
authors.affiliation: Groupe de Recherche en Biologie Végétale (GRBV), Université du Québec à Trois-Rivières, Trois-Rivières, Québec, Canada G9A 5H7.
authors.forename: Maha
authors.initials: M
authors.lastname: Zaghdoudi
authors.forename: Najoua
authors.initials: N
authors.lastname: Msilini
authors.forename: Sridharan
authors.initials: S
authors.lastname: Govindachary
authors.forename: Mokhtar
authors.initials: M
authors.lastname: Lachaâl
authors.forename: Zeineb
authors.initials: Z
authors.lastname: Ouerghi
authors.forename: Robert
authors.initials: R
authors.lastname: Carpentier
mesh_terms: D001665:Binding Sites; D004579:Electron Transport; D007700:Kinetics; D010084:Oxidation-Reduction; D045331:Photosystem I Protein Complex / Q000037:antagonists & inhibitors* / Q000378:metabolism; D045332:Photosystem II Protein Complex / Q000037:antagonists & inhibitors* / Q000378:metabolism; D010971:Plastoquinone / Q000737:chemistry; D012965:Sodium Chloride / Q000494:pharmacology*; D013050:Spectrometry, Fluorescence; D029910:Trigonella / Q000378:metabolism*
chemical_list: D045331:Photosystem I Protein Complex; D045332:Photosystem II Protein Complex; D012965:Sodium Chloride; D010971:Plastoquinone