Impacts of infection by parasitic angiosperms on host photosynthesis

Parasitic angiosperms are a taxonomically diverse group of plants that inva de host tissues and remove resources via a specialized structure known as t he haustorium. Through the haustorium, carbon, water and mineral nutrients are withdrawn, often at the expense of host growth and vigour. In addition to the removal of resources from host plants, many parasitic angiosperms ar e also able to impact host growth via effects on host photosynthesis. In th is paper we review what is known about how parasitic angiosperms affect hos t photosynthesis and the impact this has on host productivity. Holoparasite s, that lack chlorophyll, act as extra sinks for host photosynthates and ge nerally either enhance or have a neutral effect on host photosynthetic prod uctivity. In contrast, hemiparasites, that are capable of some autotrophic carbon fixation, usually have a negative impact on host photosynthesis. Irr espective of the outcome of infection, the mechanisms involved in altering host photosynthesis are diverse and may act at either the leaf or whole-pla nt level. In some cases, parasites impact directly on host photosynthetic m etabolism, while in others the effects are more indirect, for example throu gh changing host architecture.