Biosynthesis of chlorophyll b in pigment mutant C-2A' of Scenedesmus obliquus

It is demonstrated that chlorophyll b does not only derive from chlorophyll a , but is also formed separately from an in vivo-occurring chlorophyllide b . The branching point for the latter synthesis is at the level of chlorophyllide, since no protochlorophyllide b was detectable. We have indications that the enzyme oxidizing chlorophyll a to chlorophyll b accepts also non-phytylated 17,18 dihydroporphyrins and is not restricted to chlorophylls. Preparations of chlorophyllide a and chlorophyll a could both be transferred with the same enzyme fraction to chlorophyllide b and chlorophyll b , respectively. Preliminary experiments show this enzyme to be membrane bound and light independent. An updated scheme for chlorophyll b biosynthesis is presented.     

The Effect of Food Concentration on the Life History of Three Types of Brachionus calyciflorus Females

The effect of food concentration on the life history of three types of Brachionus calyciflorus females (amictic, unfertilized mictic and fertilized mictic female) was studied with replicated individual cultures at 25 ° and at four food concentrations (1.5, 3.0, 6.0 and 9.0 × 10⁶ cells mL^—1) of Scenedesmus obliquus. There were highly significant effects of both food concentration and female type, independently and in interaction on the duration of juvenile period of the rotifer, but neither were the effects on the duration of post‐reproductive period and mean life‐span. The duration of juvenile period of unfertilized mictic female at the food concentration of 9.0 × 10⁶ cells mL^—1 was the longest among all the food concentration‐female type combinations. Both food concentration and female type influenced significantly the duration of reproductive period and the number of eggs produced by each type of female per life cycle, respectively. There was, however, no significant interaction between food level and female type. Among the three types of females, the number of eggs produced by an unfertilized mictic female was the largest, and that of a fertilized mictic female was the smallest.