J. Naus et al., TRANSITIONS IN THE THYLAKOID MEMBRANES OF BARLEY LEAVES STUDIED BY CHLOROPHYLL FLUORESCENCE TEMPERATURE CURVE, Photosynthetica, 27(4), 1992, pp. 563-570
Chlorophyll (Chl) fluorescence temperature curve (FTC) of primary leav
es of spring barley (Hordeum vulgare L.), cultivated under a low irrad
iance, was studied at low actinic radiation excitation (436 nm, 2 W m-
2) under a heating regime consisting of a linear increase of temperatu
re (0.083-degrees-C s-1), followed by a period of constant temperature
. After prompt cooling of the sample to 77 K, Chl fluorescence spectra
at defined points of the temperature regime were measured. Two distin
ct temperature and kinetic regions expressed by two discernible temper
ature maxima were observed for this type of the FTC. Two triggering te
mperatures of successive irreversible changes are postulated at 45-48-
degrees-C and 53-55-degrees-C temperature intervals, respectively; the
y may correlate with the heat inactivation of photosystem 2 and with c
hanges of the chloroplast and cytoplasmic membrane integrity.