Parasitic Mode of Nutrition in Angiosperms

Parasitic angiosperms take their nutrients from a living host plant and, in doing so, damage or disease it. They fall into two groups depending on how completely they depend on the host. Obligate or total parasites depend entirely on the host for survival and always produce a specialised absorptive organ, the haustorium, that penetrates host tissue; total stem parasites, such as the leafless Cuscuta (dodder), twine their stem around a host - commonly Zizyphus or Citrus - and tap it for water, minerals and food via haustoria, while total root parasites, such as Rafflesia, Orobanche and Balanophora, have no stem axis of their own and instead grow directly in a host's roots. Partial parasites, by contrast, retain their own chlorophyll and photosynthesise their own carbohydrates, depending on the host only for water and minerals; partial stem parasites such as Loranthus and Viscum (mistletoe) grow on trees such as fig and mango, tapping the host's xylem for water and m …