Photosynthesis & Respiration in Developing Fruits. III. Variations in Photosynthetic Capacities during Color Change in Citrus.

Several studies have been made which show some of the influences of photosynthesis in the green layers of fruits upon the development of that fruit (1, 2, 3, 4, 6). During the major part of growth in oranges, lemons, and avocados, chlorophyll does not limit photosynthesis at constant light intensities (5). as might be expected. However, during the period of color change in fruits it would be possible that chlorophyll. or chlorophyll containing cells might become a limiting factor and this phase of growth has not been studlied previously. Citrus fruits are admirably suited for a study of photosynthetic changes during de-greening since the transition in these fruits (loes not necessaril) coincide with the other abrupt changes frequently associated with ripening and color change in other fruits. Changes of composition during this period nmay be very slight. In addition, the peel structure of the citrus fruit makes it possible to obtain relatively small samiiples of external tissue with a mlinimiium of (lamiiage for use in tracer studies.