All living organisms emit ultra-weak photon emission as a result of oxidative processes caused by the physical or chemical stress factors. In the present study, the effect of oxidative stress induced by the exposure of the plant model Arabidopsis thaliana to ultraviolet A (UVA) radiation was studied using ultra-weak photon emission. When Arabidopsis plants and leaves were exposed to UVA radiation, two kinetically distinguished phases in the ultra-weak photon emission decay were observed: the fast decay phase (τ1=0.805±0.024 min) and slow decay phase (τ2=4.321±0.166 min). The spectral analysis of the UVA radiation-induced ultra-weak photon emission showed that the photon emission during the fast decay phase is from both blue-green and red regions of the spectrum, whereas the photon emission during the slow decay phase is solely from the blue-green region of the spectrum. These observations reveal that triplet excited carbonyls contribute to ultra-weak photon emission during both fast and slow decay phases, whereas chlorophylls participate in the ultra-weak photon emission solely during the fast decay phase. It is illustrated here that the ultra-weak photon emission serves as a non-invasive method for the monitoring of oxidative stress in plants caused by UVA radiation.

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