Intact spinach chloroplasts scavenge hydrogen peroxide with a peroxidase that uses a photoreductant as the electron donor, but the activity of ruptured chloroplasts is very low [Nakano and Asada (1980) Plant & Cell Physiol. 21: 1295]. Ruptured spinach chloroplasts recovered their ability to photoreduce hydrogen peroxide with the concomitant evolution of oxygen after the addition of glutathione and dehydroascorbate (DHA). In ruptured chloroplasts, DHA was photoreduced to ascorbate and oxygen was evolved in the process in the presence of glutathione. DHA reductase (EC 1.8.5.1) and a peroxidase whose electron donor is specific to L-ascorbate are localized in chloroplast stroma. These observations confirm that the electron donor for the scavenging of hydrogen peroxide in chloroplasts is L-ascorbate and that the L-ascorbate is regenerated from DHA by the system: photosystem I-*ferredoxin-*NADP^>glutathione. A preliminary characterization of the chloroplast peroxidase is given.

Hydrogen Peroxide is Scavenged by Ascorbate-specific Peroxidase in Spinach Chloroplasts

One of the first of the specialized agencies of the United Nations to become active, the Food and Agriculture Organization has elicited interest beyond the specialized field of agricultural economists. Attempting as it does to solve one of the very basic problems of the world, that of an adequate food supply, the organization represents a significant and hopeful international attempt to create a world in which there may actually exist “freedom from want.” The objectives of FAO, as formally expressed in the preamble to the constitution, read as follows:“The nations accepting this constitution being determined to promote the common welfare by furthering separate and collective action on their part for the purpose of raising levels of nutrition and standards of living of the people under their jurisdiction, securing improvements in the efficiency of the production of all food and agricultural products, bettering the conditions of rural populations, and thus contributing toward an expanding world economy, hereby establish the Food and Agriculture Organization of the United Nations.”

The Food and Agriculture Organization of the United Nations

1. Plant Nutrients. 2. The Soil as a Plant Nutrient Medium. 3. Nutrient Uptake and Assimilation. 4. Plant Water Relationships. 5. Plant Growth and Crop Production. 6. Fertilizer Application. 7. Nitrogen. 8. Sulphur. 9. Phosphorus. 10. Potassium. 11. Calcium. 12. Magnesium. 13. Iron. 14. Manganese. 15. Zinc. 16. Copper. 17. Molybdenum. 18. Boron. 19. Further Elements of Importance. 20. Elements with More Toxic Effects. General Readings. References. Index.

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Principles of plant nutrition

Coupling of Phosphorylation to Electron and Hydrogen Transfer by a Chemi-Osmotic type of Mechanism

Publisher Summary This chapter discusses the chemistry of submerged soils. The chemical changes in the submerged materials influence: (a) the character of the sediment or soil that forms, (b) the suitability of wet soils for crops, (c) the distribution of plant species around lakes and streams and in estuaries, deltas, and marine flood plains, (d) the quality and quantity of aquatic life, and (e) the capacity of lakes and seas to serve as sinks for terrestrial wastes. The single electrochemical property that serves to distinguish a submerged soil from a well-drained soil is its redox potential. The redox potential of a soil or sediment provides a quick, useful, semiquantitative measure of its oxidation–reduction status. Two recent developments have stimulated interest in the chemistry of submerged soils: the breeding of lowland rice varieties, with a high yield potential, and the pollution of streams, lakes, and seas, by domestic, agricultural, and industrial wastes. The chemistry of submerged soils is valuable: (a) in understanding the soil problems, limiting the performance of high-yielding rice varieties, and (b) in assessing the role of lake, estuarine, and ocean sediments as reservoirs of nutrients for aquatic plants and as sinks for terrestrial wastes.

The Chemistry of Submerged Soils

Sumnmary.-Experiments are described with a purified RNA-dependent-RNApolymerase (replicase) induced in E. coli by the RNA bacteriophage Qj3. The data demonstrate that the enzyme can generate identical copies of added viral RNA. A serial dilution experiment established that the newly synthesized RNA is fully as competent as the original viral RNA to program the synthesis of viral particles and to serve as templates for the generation of more copies. Since the data show that the enzyme is, in fact, generating replicas, an unambiguous analysis of the RNA replicating mechanism is now possible in a simple system consisting of purified replicase, template RNA, ribosidetriphosphates, arid Mg+ +.

Quenching of chloroplast fluorescence by photosynthetic phosphorylation and electron transfer.

Prof. D. R. Hoagland

Affinity of ferredoxin for electrons from water and the regulation of cyclic photophosphorylation.

Dennis Robert Hoagland: 1884-1949.

https://science.sciencemag.org/content/sci/144/3618/559.4.full.pdf

Daniel I. Arnon

Papers

Quenching of chloroplast fluorescence by photosynthetic phosphorylation and electron transfer.

Prof. D. R. Hoagland

Affinity of ferredoxin for electrons from water and the regulation of cyclic photophosphorylation.

Dennis Robert Hoagland: 1884-1949.

Oxygen Evolution Coupled with Photoreduction of Ferredoxin by Chloroplasts.