Effects of Chill Stress on Prompt and Delayed Chlorophyll Fluorescence from Leaves

Abstract
The utilization of a portable solid state device for the simultaneous measurement of prompt and delayed fluorescence transients in leaves from a variety of species [Triticum, Glycine, Robinia, Ficus, Scindapsus, Lycopersicon, Phaseolus, Tsuga, heterophylla and T. canadensis] subjected to temperature lowering was described. The induction transients of the 2 phenomena were not identical as the peak in prompt fluorescence yield always preceded that of delayed fluorescence. Temperature lowering delayed the occurrence of peak fluorescence, increased prompt fluorescence yield, decreased delayed fluorescence yield and caused the occurrence of a new, more rapid delayed fluorescence transient. Leaves from all species had qualitatively the same type of induction curves although the response to temperature differed between species. The delayed fluorescence yield of chill-sensitive species was reduced to a greater extent than that of chill-insensitive species. Cold hardening leaf material did not greatly change the fluorescence response to temperature lowering. Arrhenius plots showed a linear relationship between delayed fluorescence yield and temperature. There were no breaks that would suggest membrane lipid phase changes. Apparently thylakoid membranes of chill-sensitive species are less capable of maintaining a light-induced high energy state at low temperatures than are thylakoid membranes of chill-resistant species.

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