Produktions- und Attraktionsleistung während der Alterung der Kartoffelpflanze

Abstract

Summary The photosynthetic capacity of leaves and the sink activity of potato tubers were studied by measuring 14 CO 2 -photosynthesis, 14 C-translocation, and distribution between the ethanol soluble and insoluble (starch) fraction of tubers. Moreover, the quantity of total chlorophyll per plant and the activity of sucrose synthetase of the tubers were estimated. Investigations were performed with one-stem pot plants from the middle to the and of the vegetation period. Independent of the age of the plant about 80% of labelled assimilates formed were transferred to the tubers 50 h after starting 14 CO 2 -photosynthesis. At this time in younger plants 50–70% of the total radioactivity were detected in the insoluble (starch) fraction and 10–20% in the soluble fraction of the tubers. In tubers of senescent plants equal amounts of radioactivity (30–40%) were measured in both fractions. Apparently during a short period (from the 50th to the 52th day after planting) the starch synthesizing activity of the tubers decreased sharply. These findings were supported by a decrease of sucrose synthetase activity during this period. The tubers ceased growing at this stage. The photosynthetic capacity of plants and the quantity of chlorophyll decreased continuously during the entire experimental period. Our results do not demonstrate a causal relationship between sink activity of tubers and source activity of leaves during potato plant senescence.