This document provides information about parasitic plants. It defines parasitic plants as plants that derive some or all of their nutritional requirements from another living plant. It then classifies parasitic plants based on where they attach to the host plant and how many nutrients they obtain. Some key classifications mentioned include obligate parasites, facultative parasites, stem parasites, root parasites, hemiparasites, and holoparasites. The document also discusses the evolution of parasitic behavior in plants, seed germination strategies, host interactions, examples of parasitic plants, and plants that are parasitic on fungi.

1. Assignment on:-
Parasitic Plants
Submitted To:-
Dr. Abid Sahib
Submitted By:-
Muhammad Naveed (20)
Kishwar Iram (27)
Hassnain Laghari(17)
Muhammad Jamshaid (24)
Abdul Samad (23)
Session:-
AG-E(A)-2016-20
Bahauddin Zakariya University
Multan

2. Parasitic plant:-
Defination:-
A parasitic plant is a plant that derives some or all of its nutritional requirements from
another living plant.
Characteristics of Parasitic Plant:-
 connecting them to the conductive system – either the xylem, the phloem, or both.
 This provides them with the ability to extract water and nutrients from the host.
 Parasitic plants are classified depending on where the parasitic plant latches onto the
host and the amount of nutrients it requires.
 About 4,500 species of parasitic plant in approximately 20 families of flowering
plants are known.
Classification of Parasitic Plants:-
Obligate parasite –A parasite that cannot complete its life cycle without a host.
Facultative parasite – a parasite that can complete its life cycle independent of a host.
Stem parasite – a parasite that attaches to the host stem.
Root parasite – a parasite that attaches to the host root.
Hemi-parasite – a plant parasitic under natural conditions, but photosynthetic to some
degree. Hemiparasites may just obtain water and mineral nutrients from the host plant; many
obtain at least part of their organic nutrients from the host as well.
e.g. Mistletoe is an obligate stem hemiparasite.
Holo-parasite - a parasitic plant that derives all of its fixed carbon from the host plant.
Commonly lacking chlorophyll, holoparasites are often colors other than green.e.g. Dodder
is a stem holoparasite.
Evolution of parasitic behaviour:-
Parasitic behavior evolved in angiosperms roughly 12-13 times independently, a classic
example of convergent evolution.
The taxonomic family Orobanchaceae is the only family that contains both holoparasitic and
hemiparasitic species, making it a model group for studying the evolutionary rise of
parasitism. The remaining groups contain only hemi-parasites or holo-parasites.
The evolutionary event which gave rise to parasitism in plants was the development of
haustoria. The first, most ancestral, haustoria are thought to be similar to that of the
facultative hemiparasites within Tryphysaria, lateral haustoria develop along the surface of
the roots in these species. Later evolution led to the development of terminal or primary
haustoria at the tip of the juvenile radicle, seen in obligate hemiparasitic species within

3. Striga. Lastly, obligate holoparasitic behavior originated with the loss of the photosynthetic
process, seen in the Orobanche genus.
To maximize resources, many parasitic plants have evolved self-incompatibility, to avoid
parasitizing themselves.
Seed germination:-
Parasitic plants germinate in a variety of ways. These means can either be chemical or
mechanical and the means used by seeds often depends on whether or not the parasites are
root parasites or stem parasites.
Root parasitic plant seeds tend to use chemical cues for germination. In order for
germination to occur, seeds need to be fairly close to their host plant. For example, the seeds
of witchweed (Striga asiatica) need to be within 3 to 4 millimeters (mm) of its host in order to
pick up chemical signals in the soil to signal germination. This range is important because
Striga asiatica will only grow about 4 mm after germination.
Stem parasitic plants, unlike most root parasites, germinate using the resources inside their
endosperms and are able to survive for some time. For example, the dodders (Cuscuta spp.)
drop their seeds to the ground; these may remain dormant for up to five years before they a
host plant nearby.
Host Interactions:-
The modes of host selection and specialization of parasitic plants is extraordinarily broad.
Castilleja and Cuscuta (dodder) can parasitize hundreds of different hosts in diverse families;
in contrast, Epifagus virginiana (beech drops) occurs only on Fagus grandifolia (beech). The
same generalization can be made about mistletoes in which some species are generalists and
others specialists. Evidence exists that the generalist strategy has the greatest chance for
survival over evolutionary time.
The terms host range versis host preference describe different aspects of the parasitic
relationship. Host range refers to the total number of different species that can be parasitized.
For example, Seymeria cassioides invariably attacks pines in nature.
Importance of Parasitic Plant:-
Species within Orobanchaceae are some of the most economically destructive species on
Earth. Species of Striga alone are estimated to cost billions of dollars a year in crop yield loss
annually, infesting over 50 million hectares of cultivated land within Sub-Saharan Africa
alone. Striga can infect both grasses and grains, including corn, rice and Sorghum,
undoubtedly some of the most important food crops. Orobanche also threatens a wide range

4. of important crops, including peas, chickpeas, tomatoes, carrots, and varieties of the genus
Brassica (e.g. cabbage, lettuce, and broccoli).
 Mistletoes cause economic damage to forest and ornamental trees.
 Rafflesia arnoldii produces the world's largest flowers at about one meter in diameter.
It is a tourist attraction in its native habitat.
 Sandalwood trees (Santalum species) have many important cultural uses and their
fragrant oils have high commercial value.
 Indian paintbrush (Castilleja linariaefolia) is the state flower of Wyoming.
 The Oak Mistletoe (Phoradendron serotinum) is the floral emblem of Oklahoma.
 A few other parasitic plants are occasionally cultivated for their attractive flowers,
such as Nutysia and broomrape.
 Parasitic plants are important in research, especially on the loss of photosynthesis
during evolution.
 A few dozen parasitic plants have occasionally been used as food by people.
 Western Australian Christmas tree (Nuytsia floribunda) sometimes damages
underground cables. It mistakes the cables for host roots and tries to parasitize them
using its sclerenchymatic guillotine.
 Some parasitic plants are destructive while some have positive influences in their
communities. Some parasitic plants damage invasive species more than native
species. This results in the reduced damage of invasive species in the community.
 Newly emergent snow plant (Sarcodes sanguinea), a fungus parasite
 In many regions, including the Nepal Eastern Himalayas, parasitic plants are used for
medicinal and ritual purposes.
Plants parasitic on fungi:-
About 400 species of flowering plants, plus one gymnosperm (Parasitaxus usta), are parasitic
on mycorrhizal fungi. This effectively gives these plants the ability to become associated
with many of the other plants around them. They are termed myco-heterotrophs. Some
myco-heterotrophs are Indian pipe (Monotropa uniflora), snow plant (Sarcodes sanguinea),
underground orchid (Rhizanthella gardneri), bird's nest orchid (Neottia nidus-avis), and
sugarstick (Allotropa virgata). Within the taxonomic family Ericaceae, known for extensive
mycorrhizal relationships, there are the Monotropoids. The Monotropoids include the
genera Monotropa, Monotropsis, and Pterospora among others. Myco-heterotrophic
behavior is commonly accompanied by the loss of chlorophyll.
Host range:-
Some parasitic plants are generalists and parasitize many different species, even several
different species at once. Dodder (Cassytha spp., Cuscuta spp.) and red rattle (Odontites
vernus) are generalist parasites.

5. Aquatic parasitic plants:-
Parasitism also evolved within aquatic species of plants and algae. Parasitic marine plants are
described as benthic, meaning that they are sedentary or attached to another structure. Plants
and algae that grow on the host plant, using it as an attachment point are given the
designation epiphytic (epilithic is the name given to plants/algae that use rocks or boulders
for attachment), while not necessarily parasitic, some species occur in high correlation with a
certain host species, suggesting that they rely on the host plant in some way or another.

6. References:-
Heide-Jørgensen, Henning S. (2008). Parasitic flowering plants. Leiden: Brill. ISBN 978-
9004167506.[page needed]
Nickrent, D. L. and Musselman, L. J. 2004. Introduction to Parasitic Flowering Plants. The
Plant Health Instructor. doi:10.1094/PHI-I-2004-0330-01 [1]
Westwood, James H., John I. Yoder, Michael P. Timko and Claude W. Depamphilis. "The
Evolution of Parasitism in Plants." Trends in Plant Science 15.4 (2010) 227-35. Web.
Stienstra, T. (11 October 2007). "It's no snow job - handful of redwoods are rare albinos".
San Francisco Chronicle. Retrieved December 6, 2010.
Krieger, L. M. (2010-11-28). "Albino redwoods hold scientific mystery". San Jose Mercury
News. Retrieved 2012-11-23.
"A Creepy Monster of the Forest: The Albino, Vampiric Redwood Tree". Discover Magazine
Discoblog. Retrieved 2012-11-23.