Plants have developed various photoprotective mechanisms to resist irradiation stress. One of the photoprotective mechanisms described in the literature for LHC2-containing organisms involves a down-regulation of photosystem (PS) 2 occurring simultaneously with the build-up of a proton gradient across the thylakoid membrane (ΔpH). It is often correlated with deepoxidation of xanthophylls located in LHC2. In Rhodophyta instead of LHC2, the peripheral antenna of PS2 consists of a large extramembrane complex, the phycobilisome (PBS), which transfers its excitation to the core antennae of PS2 composed of the CP43 and CP47 protein-chlorophyll complexes and there is no xanthophyll cycle. In the red alga Rhodella violacea a ΔpH-dependent chlorophyll (Chl) a fluorescence quenching can be formed. We characterised this quenching, studied the effects of various irradiances and inhibitors. Under photoinhibitory conditions, the ΔpH-dependent Chl fluorescence quenching exerts a photoprotective role and delays the kinetics of photoinhibition. It is the first time that such a photoprotective mechanism is described in PBS-containing organisms. and M. Ritz, K. V. Neverov, A.-L. Etienne.
In the Prague Dependency Treebank, a part of the texts from the Czech National Corpus is being annotated on several layers, including the underlying (tectogrammatical) representations. The usefulness of such a treebank is briefly characterized and a large set of topics is discussed for which further monographical research appears to be necessary. The future discussion and elaboration of these topics can be carried out much more effectively with the use of the annotated corpus, and the results thus gained may then serve to an enrichment of the descriptive framework and of the annotation procedure.
Individual values of syntactic and morphological attributes used in the syntactic annotation of the Prague Dependency Treebank are discussed, as well as certain more general issues concerning the relationships between the underlying and the morphemic levels (word order, deletion and others).