The import of nucleus-encoded proteins into chloroplasts is mediated by translocon complexes in the envelope membranes. A component of the translocon in the outer envelope membrane, Toc34, is encoded in Arabidopsis by two homologous genes, atTOC33 and atTOC34. Whereas atTOC34 displays relatively uniform expression throughout development, atTOC33 is strongly upregulated in rapidly growing, photo...

Polycyclic aromatic hydrocarbons (PAHs) have been widely studied with respect to their carcinogenic and mutagenic effects on animals and human cells. Phenanthrene (PHE) and fluoranthene (FLU) effects on the needle photosynthetic traits of 2-year-old Japanese red pine (Pinus densiflora Sieb. et. Zucc.) seedlings were investigated. Three months after fumigation of foliage with solutions containin...

Photosynthetic organisms have developed multiple mechanisms to protect the photosynthetic apparatus from high light stress. Plants and algae exhibit thermal dissipation of excitation energy in the membranebound light-harvesting complex of photosystem II (LHCII). In most species of cyanobacteria, which lack LHCII, light is captured by the phycobilisome, a membraneextrinsic complex attached to th...

Purple nonsulfur photosynthetic bacteria were cultured anaerobically in the absence of light by a modification of the Hungate technique. Growth was slow and resembled that of fastidious anaerobes; on yeast extract-peptone-agar medium, each cell produced about 16 descendants in 15 to 20 days. Growth was stimulated by addition of ethyl alcohol, acetate and H(2), or pyruvate and H(2). Cells grown ...

The influence of light, dark, and ambient CO(2) on nitrate assimilation in 8- to 9-day-old barley seedlings was studied. To develop the photosynthetic apparatus fully, the seedlings were grown in nitrogen-free Hoagland solution for 5 days in darkness followed by 3 days in continuous light.The seedlings reduced nitrate and nitrite in both light and dark, although more slowly in darkness. The slo...

Smirnovia iranica, a native valuable woody species from Fabaceae, is an adaptable plant of central sandy areas of Iran. Changes in chlorophyll fluorescence and photosynthetic pigments characteristics were analyzed in the course of phenological stages including vegetative, flowering, seed ripening, and seed falling stages, respectively (VS, FS, SRS, and SFS). The results obtained from analysis o...

The changes of Chl a fluorescence induction curve in response to different salinity levels in Canola (Barassica napus, L.) plants were investigated. The canola seedlings were exposed to salt stress (100 mM and 200 mM NaCl) for 7 days and Chl a fluorescence induction kinetics was analysed. By using the OJIP-test, various parameters like VJ, area, N, φPo, φEo, ψo, RC/ABS and PIABS were calculated...

Over-excitation of photosynthetic apparatus causing photoinhibition is counteracted by non-photochemical quenching (NPQ) of chlorophyll fluorescence, dissipating excess absorbed energy into heat. The PsbS protein plays a key role in this process, thus making the PsbS-less npq4 mutant unable to carry out qE, the major and most rapid component of NPQ. It was proposed that npq4 does perform qE-typ...

Analyses of the total pool of phenolic compounds and ferulic acid, as a photoprotector of the photosynthetic apparatus, and the activity of L-phenylalanine ammonia-lyase (PAL), as a key enzyme in phenolics synthesis, were carried out. Measurements were performed on drought-resistant (CHD 12, CHD 147) and -sensitive (CHD 220, CHD 247) genotypes of spring triticale during flowering under increasi...

Z. Naturforsch. 44c, 959—965 (1989); received April 19, 1989 ß-Carotene-5,6-epoxide, Photooxidation, DCMU, Carotenoids The occurrence of ß-carotene-5,6-epoxide in higher plant photosynthetic tissue is described. The compound is found in isolated chloroplasts, thylakoids and other subchloroplast particles but can only be detected in intact leaves or cotyledons of higher plants when these are exp...