Figure 3.

Polyphasic kinetics of the Chl fluorescence rise from F_o (“O”) via levels “J” and “I” to the peak (“P”) of the Kautsky curve in mature leaves of shade-grown V. surinamensis seedlings containing about 370 μmol Chl a+b m⁻² before and after direct sun exposure in the presence (+UV-B; Aclar film) and absence (−UV-B; Mylar film) of ambient UV-B radiation. The rise of F_v is depicted as a function of time (in logarithmic scale) in actinic light. A typical experiment is shown. A, Kinetics before exposure, recorded subsequent to 10 min of dark adaptation; B, kinetics after 30 min of sun exposure (PAR dose, about 2.6 mol m⁻²) and 10 min of dark adaptation; C, kinetics in the same leaves as for A and B after sun exposure followed by 90 min of recovery in low light and 10 min in the dark.