Parasitic plants use the water and nutrients of their host plants to sustain themselves. They generally don’t kill their hosts; however, they don’t benefit the hosts either. A parasitic plant has a special type of root, called the haustorium, which it uses to pierce through the host’s tissues and connect to the xylem or phloem.
More than four thousand species of parasitic plants have been identified to date, and they belong to 19 different flowering plant families. There are 6 major types of parasitic plants, and they are the holoparasites, hemiparasites, obligate parasites, facultative parasites, stem parasites, and the root parasites. Holoparasites are plants that do not have chlorophyll, and they cannot survive without parasitism, whereas hemiparasites can photosynthesize partially, and hence, they can live as parasites or on their own. Obligate parasites, on the other hand, require a host to complete a life cycle, but in the case of facultative parasites, a host isn’t needed for completing the life cycle. A stem parasite will attach itself to the stem of a host, while the root parasite will attach itself to the root.
Some of the most common parasitic plants are the several species of mistletoes that belong to the loranthaceae and viscaceae families. In fact, they make up about 75% of all parasitic plant species. Dodders cuscutaceae and broomrapes orobanchaceae are two other families of common parasitic flowering plants, and they are often found around summerhouses.
There are some general characteristics of parasitic plants. First of all, parasitic plants use the haustorium to transport nutrients and water. Secondly, they have the tendency to completely abandon their own photosynthesis sometimes. Also, parasitic plants called epiparasites can be exposed at the surface of a host’s skin, while endoparasites can be concealed within the host’s organ. Finally, parasitic plants use their vascular systems to connect to their hosts.
A parasite establishes itself through germination, and it quickly develops a modified lateral root, which is the haustorium. A disc shaped structure called the hapteron is then formed, which helps the root tip to penetrate the host and connect its own phloem or xylem to the host’s phloem or xylem.
Parasitic plants are not always despised by people. For instance, nuytsia and broomrape are parasitic plants which are cultivated in greenhouses for their beautiful flowers. There are certain parasitic plants that are used by researchers to study the evolution of photosynthesis. Moreover, about a dozen of them can be consumed as food or medicine. However, some parasitic plants are poisonous, and they may cause a variety of health problems when consumed, including intestinal problems and a weak pulse. It has been shown that consumption of the American mistletoe may result in death. There are also parasitic plants that can cause skin irritations when they are touched. Parasitic plants are generally considered detrimental to the economy, since they damage economically important plants as well as crops. The foliage of the parasites dodder and mistletoe covers the host to such an extent that almost all of the host’s foliage is not visible.
· The Parasitic Plant Connection : Detailed information on parasitic plants
· Britannica : Definition of haustorium
· UCLA Botany – Parasitic Plants : Provides information about parasitic plants
· Forms of Parasitism : Identifying the different types of parasitic plants
· Wikipedia – Mistletoe : Information on mistletoe
· Colorado State University – Dodder : Comprehensive information about dodders
· Broomrape : Information on broomrapes
· Penn State University – Parasitic Plants and Their Hosts : Research on how parasitic plants find their hosts
· ASGAP.org – Nuytsia: Information about the Nuytsia plant
· Wikipedia – Rafflesia: Information on Rafflesia, a parasitic plant with the world’s largest flower
· Access Science – Parasitic Plants : Research on parasitic plants
· National Center for Biotechnology Information – Photosynthesis of Parasitic Plants : Information about the photosynthesis process in parasitic plants
· Parasitic Plant Food : List of parasitic plants that can be used as food
· ITM Online.org – Cynomorium : Information on Cynomorium, a parasitic plant used in traditional medicine
· Botany.org – Parasitic Plants: Pictures of parasitic plants
Although the botanical features of parasitic plants such as their evolution, physiology, and anatomy have been studied in detail, not much in-depth information on the impact of parasitic plants on their hosts has been gathered, specifically from the perspective of damage caused. Nonetheless, experts agree that parasitic plants rarely kill their hosts, but they also believe that parasites and their hosts do not live happily together.