Sources of energy and inducement of nitrate reductase activity (NRA) in a host: root parasitic relationship

The root parasitic flowering plant, Alectra orobanchoides Benth., and its host, Helianthus annuus L., were cultivated and their NRA determined before and after the photosynthesizing parts of the host were removed. [U-14C] sucrose was also applied under these conditions. The NRA, although very low, increased in both the leaves of the parasite and the roots of the host after the photosynthesizing parts of the latter were removed. However, considering the very low NRA of the parasite especially, as well as the translocation tendencies of the 14C applied, it was concluded that the reduction of nitrate under these conditions, was probably mainly undertaken by the roots of the host, while the leaves of the parasite served as the source of photosynthetates