Norman I. Bishop

[3] Preparation and photosynthetic properties of synchronous cultures of Scenedesmus

Publisher Summary This chapter discusses the preparation and photosynthetic properties of synchronous cultures of Scenedesmus . To obtain a synchronized culture requires only that all life cycles be initiated simultaneously. This requires that at any time during the life cycle of the cells, the distribution curves of cell size are different. Distribution curves for both culture types are illustrated in the chapter. The development of a synchronized culture requires at least one discontinuous growth factor, which causes the synchronization. In the ease of green algae, the most useful parameter is light. The dilution with fresh nutrient medium is mostly done once during a life cycle, but might be performed—for certain experimental reasons—continuously during the light period. A synchronized culture is never in a steady state and only temporarily in a logarithmic growth phase. Among the different procedures for synchronizing green algae, the light-dark regime combined with a dilution to a constant cell number after each life cycle is the most appropriate.

The mechanism of the photochemical activity of isolated chloroplasts. I. Effect of temperature.

Abstract 1. 1. The rate-limiting step in the dark process of the Hill reaction has the same activation energy of 10 kcal. for several varieties of the species Beta vulgaris . 2. 2. The loss of Hill-reaction reactivity of isolated chloroplast fragments is due to at least two different processes: one, significant at temperatures greater than 30 °C., is first-order and demonstrates the characteristics of thermal denaturation of proteins; another, significant at both low and high temperatures, is second-order and has an activation energy of 8 kcal. Both reactions appear to involve participation of at least one common chloroplast substance. 3. 3. Some samples of chloroplast fragments prepared under nitrogen rather than air can be activated by incubation to a Hill-reaction reactivity as much as 50% higher than normal.