Synchronization of cell division ofChlorella pyrenoidosa

A modification of the synchronization method forChlorella pyrenoidosa was suggested, based on the mechanical separation of small and large cells by differential centrifugation and dilution of the population after division to a constant density (maximally 3×10⁶ cells/ml.). Using this system, with a 16-hour day and eight hours' darkness, the ontogenetic cycle ofChlorella pyrenoidosa takes 24 hours and synchronous growth and development can be maintained for eight generations.     

Ultrastructure of the surface of multiple scars inSaccharomycodes ludwigii

The use of induced primuline fluorescence led to the discovery of a new type of yeast scars (multiple scars) in the generaKloeckera, Saccharomycodes, Nadsonia andHanseniaspora. The structure and ultrastructure of their surface was studied by electron microscopy, using carbon replicas and isolated cell walls.     

Biosynthesis of methionine in an ethionine-resistant strain ofCandida utilis

The strainCandida utilis T 20 adapted to a high concentration of ethionine, excretes considerable amounts of methionine in a synthetic medium, about 40 times as much as the original non-adapted strain. At the same time, the amount of methionine in yeast cells incrncreased, predominantly in the pool (9 times as much as in the control). This ability to produce greater amounts of methionine in the pool or to excrete it into the medium is not permanent, since after 5 passages on agar with ut ethionine the amount of methionine was practically not increased as compared with the original non-adapted strain. An increase in free methionine and of methionine excreted into the medium was found on cultivating the strain in a molasses-containing medium, too.     

Die Wirkung von Kinetin, 2,4-DNP und Antimetaboliten auf die Veränderungen im Aminosäurengehalt welkender Pflanzenblätter

Summary It has been established that in intact plants suffering from scarcity of water as well as in isolated withering leaves the amount of proline increases considerably. The main factor in the isolated leaves is thus the scarcity of water and not the injury due to the defoliation. The proline content of the leaves withering in the dark increases only for a few days and then decreases with the diminution of the carbohydrates. Of the active substances tested only 2,4-DNP inhibited the proline synthesis during the withering. It is very probable that in the course of withering the great amount of proline forms during the oxidation of carbohydrates via -ketoglutarate. The oxydative phosphorylation is uncoupled by 2,4-DNP. Kinetin, 2,4-D and antimetabolites applied do not inhibit the abnormal increase of proline.     

Pigment composition and plastid structure in leaves of carotenoid mutants of maize

Summary In monogenic, recessive chloroplast mutants of maize which contain chlorophylls, and lycopene or -carotene but no normal carotenoids, great variability in the size of plastids was associated with a number of ultrastructural abnormalities. In the mutant accumulating lycopene some plastids contain dense bundles of lamellae, whereas the chloroplasts of the -carotene mutant show poor thylakoid development. Neither of the mutants was able to form normal grana.A comparison of chlorophyll/carotenoid ratios in different chloroplast fractions of normal and mutant leaves showed that plastids of small size and delicate structure contain relatively less chlorophyll than fully differentiated chloroplasts.