Influence of kinetin on protochlorophyll(ide) accumulation and on the Shibata shift in Raphanus seedlings

Radish seedlings (Raphanus sativus L. Saxa Treib) were grown in the dark with or without added kinetin (2 mg/l=9.29 μM). Low-temperature (77°K) fluorescence emission and absorption spectra of etiolated cotyledons were registered at increasing seedling age before and immediately, 30 s and 30 min after one 1-ms flash. Kinetin was found to induce a higher accumulation of the phototransformable protochlorophyll(ide) P657-650 in the etiolated cotyledons, especially from day 6 to day 10 after germination. The amount of the P657-650 protochlorophyll(ide) resynthesized during a 30-min dark period after a 1-ms flash decreased with seedling age. It was smaller in cotyledons from kinetin-treated seedlings at day 6 after germination and at that age only. The ability to perform the Shibata shift decreased with increasing seedling age. In cotyledons from 10- and 13-day-old seedlings, the shift was accomplished to a greater extent when the plants were grown in the presence of kinetin.