Chloroplasts are a characteristic feature of green plants. Mesophyll cells possess the majority of chloroplasts and it is widely believed that, with the exception of guard cells, the epidermal layer in most higher plants does not contain chloroplasts. However, recent observations on Arabidopsis thaliana have shown a population of chloroplasts in pavement cells that are smaller than mesophyll ch...

1. Ammonium chloride is a poor uncoupler of photophosphorylation in subchloroplast particles. In the presence of valinomycin the inhibition of photophosphorylation by NH&l is greatly enhanced. 2. The enhancement of the ammonium chloride uncoupling of phosphorylation by valinomycin was less pronounced in chloroplasts than in subchloroplast particles. 3. The light-dependent uptake of ammonium ion...

Absolute DNA amounts of individual chloroplasts from mesophyll and epidermal cells of developing spinach leaves were measured by microspectrofluorometry using the DNA-specific stain, 4,6-diamidino-2-phenyl indole, and the bacterium, Pediococcus damnosus, as an internal standard. Values obtained by this method showed that DNA amounts of individual chloroplasts from mesophyll cells fell within a ...

Chloroplasts are organelles with many vital roles in plants, which include not only photosynthesis but numerous other metabolic and signaling functions. Furthermore, chloroplasts are critical for plant responses to various abiotic stresses, such as salinity and osmotic stresses. A chloroplast may contain up to ~3,000 different proteins, some of which are encoded by its own genome. However, the ...

Manganese is involved in the photosynthetic reactions of algae and leaves of higher plants (1-3). In tomato, manganese deficiency results in chloroplasts with a greatly reduced Hill reaction activity per unit chlorophyll (3). In spinach, manganese deficiency causes a 50 to 70 per cent reduction in the FMN-mediated photophosphorylation of isolated chloroplasts but only slightly affects the phosp...

Polyphenol oxidase of leaves is located mainly in chloroplasts isolated by differential or sucrose density gradient centrifugation. This activity is part of the lamellar structure that is not lost on repeated washing of the plastids. The oxidase activity was stable during prolonged storage of the particles at 4 C or -18 C. The Km (dihydroxyphenylalanine) for spinach leaf polyphenol oxidase was ...

Treatment of spinach chloroplasts with 25 to 100 pM potassium permanganate in the presence of light, magnesium, and ADP gives rise to 35 to 60% inhibition of the subsequent phosphorylation and ATPase activities. For half-maximal inhibition, 5 to 10 PM ADP is necessary and ADP is not replaceable by other nucleotides. The light requirement can be met by preillumination as well as by an acid bath ...

The energy status of plant cells strongly depends on the energy metabolism in chloroplasts and mitochondria, which are capable of generating ATP either by photosynthetic or oxidative phosphorylation, respectively. Another energy-rich metabolite inside plastids is the glycolytic intermediate phosphoenolpyruvate (PEP). However, chloroplasts and most non-green plastids lack the ability to generate...

Extracts of leaf tissue of Zea mays L. seedlings were fractionated on nonlinear sucrose gradients to separate subcellular organelles. Homoserine dehydrogenase (EC 1.1.1.3) was identified in those fractions containing intact chloroplasts, as judged by the presence of chlorophyll and triosephosphate isomerase activity. Neither enzyme activity was detected in fractions containing ruptured chloropl...

1. Chloroplasts prepared by the non-aqueous technique will, after fragmentation by ultrasonic treatment, incorporate [2-14C]mevalonic acid into phytoene, the first C40 compound formed in the biosynthetic sequence to coloured carotenoids. 2. With suspensions containing 3*5mg. of chlorophyll, the optimum amounts of cofactor required were ATP (10,umoles), magnesium chloride (20,umoles) and glutath...