The Influence of Dark Adaptation Temperature on the Reappearance of Variable Fluorescence following Illumination

The effect of chilling temperatures (5°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°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°C following illumination resulted in a much faster return of $F_{v}$ than dark adaptation at 5°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.