Dynamics of some photosynthetic parameters was studied in gametes, zygotes, and embryos of kelp Fucus vesiculosus L. The following indices were determined at different stages of seaweed early development: the contents of pigments and ribulose-1,5-bisphosphate carboxylase/oxygenase, the rates of photosynthesis and dark respiration, and the activities of photosystems I and II. The dynamics of photosynthetic activity in the zygotes and embryos of F. vesiculosus proved to reflect the main physiological processes of its early development.
PLANT PHYSIOLOGY
Three species of Fucus inhabiting different zones at the littoral and sublittoral of the White Sea (F. vesiculosus L., F. serratus L., and F. distichus L.) were compared with regard to performance of the pho tosynthetic apparatus (PSA) and PSA changes upon prolonged desiccation of algae. The content of chloro phyll a and the total content of carotenoids were significantly higher in F. serratus than in F. vesiculosus. The potential quantum yield (F v /F m ) of photosystem II (PSII) was 0.69-0.74 in all species. The highest effective quantum yield of PSII (Y II ) was observed in F. vesiculosus plants inhabiting zones with the most intense inso lation. The ratio of non photochemical quenching to photochemical quenching (qN/qP) increased with the depth of algal habitats in the row from F. vesiculosus to F. serratus. The fluorescence parameters F. serratus deviated during desiccation from their normal values and did not recover upon the subsequent return to water. By contrast, the fluorescence parameters of F. vesiculosus and F. distichus recovered gradually after the return of algae from air to sea water. It is supposed that F. serratus plants, unlike other species, are characterized by comparatively low physiological plasticity.Abbreviations: ETR-electron transport rate (relative units); F 0 and F m -chlorophyll fluorescence intensities in the states with open and closed reaction centers, respectively; F v /F m -potential quantum yield of photosystem II photoreaction in the dark adapted state; PSA-photosynthetic apparatus; PSI and PSIIphotosystems I and II; qN-coefficient of non photochemical quenching of chlorophyll fluorescence; qP-coefficient of photo chemical quenching of fluorescence; Y II -effective quantum yield of PSII photoreaction in the light adapted state.
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