Sink-stimulated photosynthesis, increased transpiration and increased demand-dependent stimulation of nitrate uptake: nitrogen and carbon relations in the parasitic association Cuscuta reflexa-Coleus blumei

When parasitizing Coleus blumei Benth., grown in quartz sandculture and fed with 0.2, 1 or 5 mM nitrate, the biomass productionof Cuscuta reflexa Roxb. was inhibited to a similar extent asthat of the host supplied limiting concentrations of nitrate.In the presence of Cuscuta the growth and dry matter increaseof the host plant was severely inhibited. However, dry matterproduction of host plus parasite was only slightly less thanor at 0.2 mM nitrate almost the same as that of uninfected Coleusplants. Under all conditions of nitrate nutrition, parasitismby Cuscuta led to a substantial increase in photosynthesis inhost leaves under light-saturating conditions and in transpiration.Particularly with 0.2 mM and mM