The formation of S-aminolevulmic acid (ALA), energy-dependent steps ffom ALA to protoporphyrin IX (Proto) and from Proto to protochlorophyllide (PChlide) formation, the roles of NADPH in PChlide photoreduction and geranylgeraniol hydrogenation, the source of adenylates and reduced pyridine nucleotides for the reactions of chlorophyll biosynthesis, and the compartmentation and interrelationships of porphyrin biosynthesis pathways are reviewed.
Oxygen deficiency is a widespread stress factor. Its consequences studied with the seedlings of Triticum aesíivum, under a special consideration of their root growth and morphology, the gas exchange and pyridine nucleotide systém, and the chlorophyll biosynthesis in shoots, are reviewed here on the basis of the general stress concept.
Etiolated oat mesophyll protoplasts and etioplasts released from etiolated protoplasts were able to perform protochlorophyliide (PChlide) reduction but showed a high amount of inactive P633/628» compared with intact leaves. In špite of this, the anabolic reduction charge (ARC, NAPDH+H+/NADP+ + NADPF1+H+) was maintained at 0.66 - 0.77 up to 30 min of irradiation with weak "white light" (10 W m‘2). This indicated a high buffering capacity of the isolated systém to provide NADPF1+H+, only at the expense of intemal reserves. A change in the redox statě of the NADP+/NADPH+H^ couple during protochlorophyliide reduction was not observed in etioplasts. The resulting redox potential was in the range of -330 mV optimal for protochlorophyliide reduction.
Sarcocysts were found in muscle tissue of a wisent (Bison bonasus) which was born and kept in Germany. Light microscopic and ТЕМ examination revealed all the Ihrcc named species known from cattle: Sarcocystis cruzi („thin-walled“, with longer hairlike villar protrusions of the primary cyst wall); S. hirsuta („thick-walled“, with tongue-like protrusions of the cyst wall arising with very short and narrow stalklets from the surface of the cyst and containing rows of electron-dense granules in the core); and S. hominis („thick-walled“, with fmger-like protrusions of the cyst wall not constricted at their base and containing few or no electron-dense granules). So far, only S. cruzi was known to occur in Bison bison in North America. The findings in the wisent strikingly support a modified conception of the intermediate host specificity in Bovinae. In this connection the identity of S. cruzi and S. poephagicanis is suggested as well as that of S. hirsuta and S. poepliagi.