Thermally Induced Chemiluminescence of Barley Leaves

Abstract

Abstract- An unconventional band in the thermoluminescence glow curve of barley leaves at about +50°C was examined. In contrast to bands usually observed around +50°C, this band (designated as CL) is not related to photosynthetic electron transport in photosystem II. The appearance of the CL band (1) requires previous freezing of the sample, (2) is not influenced by light excitation and (3) depends on the presence of oxygen. In pure oxygen the glow curves for both leaves and chloroplast suspension exhibit three maxima at about +40°C, +65°C and +90°C. Based on the emission spectra of the CL band and measurements with etiolated leaves, we suppose that the majority of emission corresponding to the CL band originates from chlorophyll. A lipoxygenase inhibitor, butylated hydroxytoluene, and sodium azide decrease the intensity of the CL band. We propose that the mechanism leading to emission of the CL band involves thermally stimulated production of an active oxygen species that results in lipid peroxidation.

The mechanism of the ozone-induced changes in thermoluminescence glow curves of barley leaves

“…The band was found under heating of leaves in nitrogen atmosphere and its intensity was not lower in nitrogen than in air and oxygen. In contrast to these results, the earlier reported chemiluminescence band did not appear under nitrogen atmosphere (Skotnica 1999). The ozone-induced band was re-activated after 1 single-turnover flash.…”

“…If the sample was heated in nitrogen atmosphere, the intensity was not significantly different from that under heating in the presence of oxygen. This behaviour is opposite to that observed for the CL band previously described in barley leaves (Skotnica et al 1999). It indicates that the 55 °C band is not an oxygendependent CL band, but is related to PS2 photochemistry.…”

“…In leaves, the main candidates for the explanation of an ozone-induced band at about 55 °C could be the classical C-band or a contribution of an oxygendependent chemiluminescence band (Skotnica et al 1999). The experiments with dark-adaptation and different atmospheres after the treatment with ozone support the relation of the band to PS2 photochemistry.…”

“…The band at 55 °C: Several different bands were described at about 50 °C in thermoluminescence glow curve (Desai et al 1975, Rózsa et al 1989, Skotnica et al 1999. In leaves, the main candidates for the explanation of an ozone-induced band at about 55 °C could be the classical C-band or a contribution of an oxygendependent chemiluminescence band (Skotnica et al 1999).…”

“…Rózsa et al (1989) observed a lightinduced band in various sub-chloroplast preparations obtained by detergent treatment as well as with artificially prepared protein-pigment-detergent micelles. Skotnica et al (1999) characterized a chemiluminescence band at about 50 °C in TL glow curves of barley leaves. The appearance of the band was dependent on the presence of oxygen during heating of the sample.…”