Photosynthetic characteristics of detached barley leaves during greening in the presence of SAN 9785

Abstract

The effects of the pyridazinone compound SAN 9785 on the photosynthetic competence of leaves, on the photochemical activity of isolated thylakoids and on the formation and spectral properties of chlorophyll-protein complexes were studied during a 72-h greening period of detached etiolated leaves of barley (Hordeum vulgare L. cv. Horpácsi kétsoros). It was established that i) the photosynthetic capacity of the leaves decreased considerably (by 80 and 90%, as determined by(14)CO2 fixation and fast fluorescence induction measurements, respectively); ii) the photochemical activity of isolated thylakoids from water to potassium ferricyanide and from dichlorophenol indophenol/ascorbate to methylviologen exhibited only slight reductions when expressed on a chlorophyll basis compared with the control; iii) the slow fluorescence induction curves of the treated leaves demonstrated the presence of a peculiar fluorescence component interrupting the quenching of fluorescence at around 1 min illumination; iv) a shortage of the chlorophyll-protein complex of photosystem I (CPI) occurred with a higher content of the monomer of the light harvesting complex in the thylakoids of treated leaves; and v) the fluorescence spectrum of the CPI band present in treated leaves indicates the destruction of the structural integrity of this complex during isolation from the membrane.

Structure-Function-Relationship in Thylakoids Influenced by the Pyridazinone BAS 13–338 (SAN 9785)

“…In addition, our results indicate that energy transfer between different pigment protein complexes depends on close distances between them and could be influenced by the state of the lipid matrix . These findings are in agreement with the proposed relationship between pyrid azinone induced altera- tions in linolenic acid content and fluorescence induction in vivo (18) . Calculations in [19] propose that in appressed regions, there is a minimum set-up of acyllipids which favour energy transfer between pigment protein complexes.…”

Structure-Function-Relationship in Thylakoids Influenced by the Pyridazinone BAS 13—338 (SAN 9785)

“…In addition, our results indicate that energy transfer between different pigment protein complex es depends on close distances between them and could be influenced by the state of the lipid matrix. These findings are in agreem ent with the proposed relationship between pyridazinone induced altera tions in linolenic acid content and fluorescence in duction in vivo [18].…”