Photosynthetic activities in the petunia corolla.

Pink Petuniahybrida (cv Hit Parade Rosa) corollas were found to contain photosynthetically active chloroplasts. The corolla chloroplasts were similar to those of green leaves in size and structure. The chlorophyll (Chl) content of Petunia corollas increased during early stages of flower development, reaching a maximum just before anthesis. Chloroplasts isolated from corollas at this stage, carried out photosystem I-dependent electron transport at rates which were two-thirds of those measured in chloroplasts from green leaves, but full chain electron transport at only one-quarter of the rate carried out by chloroplasts from green leaves. Both the light saturated rate and the quantum yield for electron transport were lower in corolla chloroplasts, which also required lower intensities for light saturation. Reduced efficiency of photosystem II photoreactions in the corolla was also indicated by the ratio between variable and constant components of Chl fluorescence, which was lower in corollas compared to green leaves. The induction time of Chl fluorescence was at least three times shorter in corollas compared to green leaves, indicating a smaller number of functional photosystem II centers (per Chl) in the corolla. It is suggested that corolla chloroplasts of Petunia might have a role in flower developmental processes.