Parasitic Plants


NARRATOR: Some plants
spend their lives stealing from other plants
and are known as parasites. Parasites are
organisms that derive some or all of their
nutrients from other organisms in a way that is not
mutually beneficial. Mistletoe is a parasitic plant. It can only exist by
growing on another tree, as it has no roots. Mistletoe grows on
branches of host trees, tapping into the
plant’s transport system to steal water and sugary sap. Most mistletoe species
have green leaves, enabling them to manufacture
some food by photosynthesis. But many parasitic plants
can’t even manage that. This dodder vine is germinating. A totally parasitic plant, its
seeds must quickly find a host or they will die. Not even a nettle sting
will deter the dodder. The seedlings suck the sap
from the nettle’s stem, fueling the dodder’s growth. And when it has enough
nourishment, it will flower. A single dodder
seedling may, in time, overwhelm a whole
bed of nettles. The mistletoe and
dodder vine rely on their hosts staying alive. But one plant sets out
to kill its victim. A young fig tree grows slowly
on the branch of its host. Its roots crawl
over the branches, and some head for the ground. Supplied with nutrients, it
now grows extremely quickly, its rootlets wrapping around
the host’s trunk, forming a web. The host tree is being killed. This is a strangler fig. Over several years,
the fig roots will strangle the trunk,
stealing most of the nutrients from the soil and
blocking sunlight from reaching the host’s leaves. The host tree will
eventually die. As its trunk rots away,
the fig remains standing, as its roots have formed a
hollow cylinder strong enough to support it. The plant world is filled
with parasitic plants, some just looking for an easy ride,
but others are out to kill.

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