In leaves of spinach plants (Spinacia oleracea L.) performing CO(2) and NO(3) (-) assimilation, at the time of sudden darkening, which eliminates photosystem I-dependent nitrite reduction, only a minor temporary increase of the leaf nitrite content is observed. Because nitrate reduction does not depend on redox equivalents generated by photosystem I activity, a continuation of nitrate reduction...

In photosynthesizing plant cells, chloroplasts change their arrangements and/or positions in response to light irradiation. These photo-orientation movements of chloroplasts are believed to play important roles in optimizing the photosynthetic activity of plant cells. We have been investigating the roles of the actin cytoskeleton in the intracellular movement and positioning of chloroplasts usi...

HSP70s are an evolutionarily conserved family of 70-kD proteins better known as molecular chaperones (Ellis and van der Vies, 1991). Molecular chaperones assist the in vivo assembly and folding of polypeptides during normal growth without themselves becoming part of the final folded protein (Gatenby, 1992). HSP70s show differential expression to a variety of abiotic or biotic factors (for revie...

Two types of red pigment, anthocyanins and betacyanins, never occur together in the same plant. Although anthocyanins are widely distributed in higher plants as flower and fruit pigments, betacyanins have replaced anthocyanins in the Caryophyllales. We isolated cDNAs encoding dihydroflavonol 4-reductase (DFR), which is the first enzyme committed to anthocyanin biosynthesis in the flavonoid path...

Activity ratios and carbamylation ratios of ribulose-1,5-bisphosphate carboxylase (RuBPCase) were determined for leaves of Phaseolus vulgaris and Spinacia oleracea exposed to a variety of partial pressures of CO(2) and O(2) and photon flux densities (PFD). It was found that activity ratios accurately predicted carbamylation ratios except in extracts from leaves held in low PFD. In particular, i...

The present study is an attempt to investigate the radioprotective efficacy of spinach against radiation induced oxidative stress, since its leaves are rich in antioxidants like carotenoids (beta-carotene, lutein and zeaxanthin) and high content of proteins, minerals, vitamin C. For the experimental study, healthy Swiss mice were selected from an inbred colony and divided into four groups. Grou...

Results of cytochemical studies (Sagan and Scher, 1961 ; Ris and Plaut, 1962 ; Kislev et al ., 1965) and of studies involving cell fractionation and buoyant density analyses (Sager and Ishida, 1963 ; Ray and Hanawalt, 1964 ; Brawerman and Eisenstadt, 1964 ; Edelman et al ., 1964 ; Wells and Birnstiel, 1969) have shown that chloroplasts of microorganisms and of higher plants contain DNA which is...

Four distinct isozymes of aspartate-alpha-ketoglutarate transaminase in a spinach (Spinacia oleracea L.) leaf extract were separated by starch gel electrophoresis. Of the total aspartate-alpha-ketoglutarate transaminase activity, approximately 45% was represented by the chloroplast isozyme, 26% by the cytosol isozyme, 19% by the mitochondrial isozyme, and 3 to 10% by the peroxisomal isozyme. Th...

Light-driven electron transfer reactions cause the active accumulation of protons inside thylakoids, yet at steady state the electrical potential difference across the thylakoid membrane is very small; therefore, there must be a flux of other ions to balance the charge that would otherwise be built up by the net movement of H(+). This paper presents direct measurements of ion movements through ...

This work represents an application of the Visible Spectrometry, High Pressure Liquid Cromatography and Electronspray Ionisation-Mass Spectrometry analysis for the identification of chlorophyll and its derivatives, pheophytin and chlorophyllide, in their purified mixtures (the chlorophyll, pheophytin and chlorophyllide fraction, respectively). The chlorophyll, pheophytin and chlorophyllide frac...