Chlorophyll fluorescence and photoinhibition in a tropical rainforest understory plant.

The data presented here deal with the effects of high-light exposure on the 77 K fluorescence characteristics of Elatostema repens. It is shown that the decrease of the variable fluorescence during the treatment is biphasic. The reactions responsible for the first phase of fluorescence quenching are saturated under 700 μmol photon m(-2) s(-1) and insensitive to streptomycin, whereas those responsible for the second phase are not yet saturated under 700 μ mol photon m(-2) s(-1) and sensitive to streptomycin. It is concluded that only the second phase of fluorescence quenching is associated with photoinhibitory processes. Rate and amplitude of recovery from photoinhibition are maximum under very low light (3.5 μ mol photon m(-2) s(-1)), and very small at a moderate light (160 μ mol photon m(-2) s(-1)) which does not cause photoinhibition. It is concluded that recovery processes are inhibited during photoinhibition. It is suggested that they could be associated with damage occuring on the oxidizing side of PSII.