Energy, Respiration, and Growth in Plants

The energy relations and heat production during plant growthare analysed in terms of respiration, dry weight, and growth.Wastage respiration and its relationship to this analysis arediscussed The results of microcalorimetric experiments on wheatseedlings are analysed and interpreted.     

Respiration rates in heterotrophic,free-living protozoa

Published estimates of protozoan respiratory rates are reviewed with the object of clarifying their value in ecological studies. The data show a surprisingly large variance when similarly sized cells or individual species are compared. This is attributed to the range of physiological states in the cells concerned. The concept of basal metabolism has little meaning in protozoa. During balanced growth, energy metabolism is nearly linearly proportional to the growth rate constant; at the initiation of starvation, metabolic rate rapidly declines. Motility requires an insignificant fraction of the energy budget of protozoans. For growing cells, metabolic rate is approximately proportional to weight^0.75 and the data fall nearly exactly on a curve extrapolated from that describing the respiration rates of poikilotherm metazoans as a function of body weight. It is conceivable that protozoan species exist with lower maximum potential growth and metabolic rates than those predicted from cell volume and the equations derived from the available data. However, the lack of information concerning the state of the cells studied prevents verification of this idea. Laboratory measurements of protozoan respiratory rates have no predictive value for protozoa in nature other than delimiting a potential range. For small protozoans, this range may, on an individual basis, represent a factor of 50.     

Advances in Photosynthesis and Respiration,Volumes 15 and 16: ‘Respiration in Archaea and Bacteria’, Edited by Davide Zannoni

Photosynthesis Research -     

Phylogenetic Analysis of Proteins Associated in the Four Major Energy Metabolism Systems: Photosynthesis,Aerobic Respiration,Denitrification, and Sulfur Respiration

The four electron transfer energy metabolism systems, photosynthesis, aerobic respiration, denitrification, and sulfur respiration, are thought to be evolutionarily related because of the similarity of electron transfer patterns and the existence of some homologous proteins. How these systems have evolved is elusive. We therefore conducted a comprehensive homology search using PSI-BLAST, and phylogenetic analyses were conducted for the three homologous groups (groups 1–3) based on multiple alignments of domains defined in the Pfam database. There are five electron transfer types important for catalytic reaction in group 1, and many proteins bind molybdenum. Deletions of two domains led to loss of the function of binding molybdenum and ferredoxin, and these deletions seem to be critical for the electron transfer pattern changes in group 1. Two types of electron transfer were found in group 2, and all its member proteins bind siroheme and ferredoxin. Insertion of the pyridine nucleotide disulfide oxidoreductase domain seemed to be the critical point for the electron transfer pattern change in this group. The proteins belonging to group 3 are all flavin enzymes, and they bind flavin adenine dinucleotide (FAD) or flavin mononucleotide (FMN). Types of electron transfer in this group are divergent, but there are two common characteristics. NAD(P)H works as an electron donor or acceptor, and FAD or FMN transfers electrons from/to NAD(P)H. Electron transfer functions might be added to these common characteristics by the addition of functional domains through the evolution of group 3 proteins. Based on the phylogenetic analyses in this study and previous studies, we inferred the phylogeny of the energy metabolism systems as follows: photosynthesis (and possibly aerobic respiration) and the sulfur/nitrogen assimilation system first diverged, then the sulfur/nitrogen dissimilation system was produced from the latter system.     

Growth, Maintenance and Respiration: a Re-interpretation

The traditional view of respiration being due to the processesof growth and maintenance is questioned. A model is proposedin which plant dry matter is divided into three categories:storage material which may be used for growth; non-degradablestructural material which cannot be recycled, and which is consideredto be inert; and degradable structural material which is assigneda rate constant of degradation, and which is considered to bebiologically active. The model has four parameters: two yieldconstants, and two rate constants, and it has been solved forsteady-state exponential growth in continuous daylight, respirationin the dark, and ^l4CO₂ evolution after a pulse label. Analysisof ^l4CO₂ efflux data leads to the complete definition of themodel. The utility and comparative merits of the suggested viewpointof respiration are discussed.     

Respiration, cyanide-insensitive oxygen uptake and oxidative phosphorylation in cyanobacteria

Cyanide-insensitive oxygen uptake in the dark of 9 species of cyanobacteria was 6–20% of the total oxygen uptake of intact cells. In Phormidium , no cyanideinsensitive oxygen uptake was observed. In intact cells, the I₅₀ value for cyanide was significantly lower in cyanobacteria of the taxonomic sections I to III (1–9 μ M ) than in those from section IV and V (10–60 μ M ). Cyanide-insensitive oxygen uptake in the cell-free system of Anabaena variabilis was not affected by typical inhibitors of the alternative pathway of plants. Cell-free oxidation of cytochrome c was completely inhibited by cyanide with an I₅₀ value of 0.5–1 μ M . Electron transport of intact cells without cyanide present yielded P/O ratios of 0.7–3.0. The data on oxidative phosphorylation using intact cells and the cell-free system, indicate that cyanide-insensitive oxygen uptake is not coupled to ATP formation.     

Starch Metabolism, Respiration, and Shoot Formation in Tobacco Callus Cultures

The starch content of shoot-forming and non-shoot-forming tobacco callus cultured in light and darkness was determined. A variety of carbohydrates and cytokinins incorporated into the culture medium were effective in bringing about starch accumulation and shoot formation in the tissue. In addition, the respiratory activity of the callus, grown in the presence or absence of gibberellic acid, was measured. A strong correlation between the starch content of the tissue, its rate of respiration, and shoot formation was observed.     

Respiration and sleep

Some of the main aspects of the relations which exist between sleep and respiratory function are discussed. Physiological data obtained both in humans and in animals are analyzed. Some results obtained in normal healthy newborns are mentioned. The sleep related respiratory diseases are not evoked here.