The effect of chilling temperatures (5 degrees C) on chlorophyll fluorescence transients was used to study chilling-induced inhibition of photosynthesis in plant species with differing chilling sensitivities. A Brancker SF-20 fluorometer was used to measure induced fluorescence transients from both attached and detached leaves of chilling-sensitive cucumber (Cucumis sativus L. cv Ashley) and chilling-resistant pea (Pisum sativum L. cv Alaska). The rate of reappearance of the variable component of fluorescence (F(v)), following a period of illumination at 25 degrees C, was dependent on the temperature at which the leaf was allowed to dark adapt in chilling-sensitive cucumber, but not in chilling-resistant pea. In cucumber, dark adaptation at 25 degrees C following illumination resulted in a much faster return of F(v) than dark adaptation at 5 degrees C following illumination. However, F(v) reappearance during the dark adaptation period in chilling-resistant pea was temperature independent. The difference in the temperature response of F(v) following illumination correlated with temperature sensitivity of these two species. The process responsible for the difference in F(v) may represent a site of chilling sensitivity in the photosynthetic apparatus.
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