title: The chl a fluorescence intensity is remarkably insensitive to changes in the chlorophyll content of the leaf as long as the chl a/b ratio remains unaffected.
abstract: The effects of changes in the chlorophyll (chl) content on the kinetics of the OJIP fluorescence transient were studied using two different approaches. An extensive chl loss (up to 5-fold decrease) occurs in leaves suffering from either an Mg(2+) or SO(4)(2-) deficiency. The effects of these treatments on the chl a/b ratio, which is related to antenna size, were very limited. This observation was confirmed by the identical light intensity dependencies of the K, J and I-steps of the fluorescence rise for three of the four treatments and by the absence of changes in the F(685 nm)/F(695 nm)-ratio of fluorescence emission spectra measured at 77K. Under these conditions, the F(0) and F(M)-values were essentially insensitive to the chl content. A second experimental approach consisted of the treatment of wheat leaves with specifically designed antisense oligodeoxynucleotides that interfered with the translation of mRNA of the genes coding for chl a/b binding proteins. This way, leaves with a wide range of chl a/b ratios were created. Under these conditions, an inverse proportional relationship between the F(M) values and the chl a/b ratio was observed. A strong effect of the chl a/b ratio on the fluorescence intensity was also observed for barley Chlorina f2 plants that lack chl b. The data suggest that the chl a/b ratio (antenna size) is a more important determinant of the maximum fluorescence intensity than the chl content of the leaf.
authors.affiliation: Institute of Plant Biology, Biological Research Center, Hungarian Academy of Sciences, H-6701 Szeged, Hungary.
authors.forename: Emine
authors.initials: E
authors.lastname: Dinç
authors.forename: M Georgina
authors.initials: MG
authors.lastname: Ceppi
authors.forename: Szilvia Z
authors.initials: SZ
authors.lastname: Tóth
authors.forename: Sándor
authors.initials: S
authors.lastname: Bottka
authors.forename: Gert
authors.initials: G
authors.lastname: Schansker
mesh_terms: D027461:Beta vulgaris / Q000187:drug effects / Q000378:metabolism / Q000528:radiation effects; D002734:Chlorophyll / Q000378:metabolism*; D000077194:Chlorophyll A; D005453:Fluorescence; D001467:Hordeum / Q000187:drug effects / Q000378:metabolism / Q000528:radiation effects; D008274:Magnesium / Q000378:metabolism; D016376:Oligonucleotides, Antisense / Q000494:pharmacology; D018515:Plant Leaves / Q000187:drug effects / Q000378:metabolism* / Q000528:radiation effects; D010940:Plant Proteins / Q000378:metabolism; D013431:Sulfates / Q000378:metabolism; D014908:Triticum / Q000187:drug effects / Q000378:metabolism / Q000528:radiation effects
chemical_list: D016376:Oligonucleotides, Antisense; D010940:Plant Proteins; D013431:Sulfates; D002734:Chlorophyll; C037184:chlorophyll b; D008274:Magnesium; D000077194:Chlorophyll A