The regularities in the alterations of chlorophyll a fluorescence induction curves of bean leaves after short (15 min) heating in the range of temperatures from 24 to 45$^\circ$C were determined. A dramatic decrease in the relative f luorescence quenching $(F_{P} –F_{T})/F_{T}$ , as well as the $F_{v} /F_{m}$ ratio, were observed after heating at temperatures above 38$^\circ$C, which indicates a decrease in the photochemical activity of photosystem II. The effect of an increase in the resistance of the photosynthetic apparatus to the temperature of 43$^\circ$C after preheating at 37$^\circ$C was demonstrated.
87.64.-t Spectroscopic and microscopic techniques in biophysics and medical physics
87.15.Mi Spectra, photodissociation, and photoionization; luminescence
Department of Physics, Moscow State University, Moscow, 119992 Russia
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