Photosynthetic properties and photosystem stoichiometry of in vitro-grown juvenile, adult, and rejuvenated Sequoia sempervirens (D. Don) Endl

Photosynthetic properties and photosystem stoichiometry of in vitro-grown juvenile, adult, and rejuvenated Sequoia sempervirens shoots were characterized. 77K fluorescence analysis indicated that photosystem II/photosystem I ratios were highest for chloroplasts in adult shoots. Photosynthetic oxygen evolution rates (on the same chlorophyll bases) were also slightly higher for chloroplasts in adult shoots. Our results suggested a significant alteration of photosystem stoichiometry in chloroplasts of Sequoia sempervirens shoots during phase change. In addition, chlorophyll a fluorescence analysis showed that juvenile, adult, and rejuvenated shoots showed virtually identical maximal quantum efficiencies of photosystem II (FV/FM). Nonphotochemical quenching (NPQ) during actinic light illumination, however, was significantly enhanced for AS76 adult shoots. The differences in photosynthetic properties and photosystem stoichiometry among juvenile, adult, and rejuvenated shoots may reflect adjustments in the photosynthetic apparatus to acclimate to distinct physiological states of Sequoia sempervirens during phase changes.