PARASITIC PLANTS

Big fleas have little fleas
upon their backs to bite 'em;
little fleas have smaller fleas,
and so ad infinitum.

To this verse, the poet Jonathan Swift added:

Thus every poet, in his kind,
Is bit by him that comes behind.

Those couplets would win no prizes, but they neatly describe the chain of events in many natural environments. For example, in the desert we often find parasitic plants such as the mistletoes, living off the resources of their host plants. There are even some mistletoes that parasitise other mistletoes! You can find an example by going to The Parasitic Plant Connection website (not on this server).

The parasitic plants can be classed into two groups, termed hemiparasites and holoparasites. Hemiparasites (e.g. mistletoes) have photosynthetic tissues and therefore can satisfy their own energy needs, but they have no roots and therefore gain their water and mineral nutrients by tapping into the tissues of a host plant. This is typically achieved by forming a special nutrient-aborbing organ called a haustorium. Holoparasites (e.g. dodder) have no photosynthetic tissues and thus depend on a host plant for all their requirements; again, they achieve this by forming an haustorium.

In some cases it is not immediately obvious that a plant is acting as a parasite. For example, this is true when a parasitic plant (a hemiparasite) is attached to the root system of another plant. There are many such examples in desert environments. For example, range ratany, owl clover and the Indian paintbrushes are all hemiparasites - they have photosynthetic leaves, but their seeds germinate and the young roots immediately attach to the root system of a host plant to supply a source of water and mineral nutrients.

In addition to the parasitic plants, several small wasps and other insects (e.g. gall midges) that lay their eggs in plants and induce a localised proliferation of the plant tissues so that these produce a nutrient-rich gall that protects and feeds the developing insect larvae.

Go to:
Mistletoes
Dodder
Insect galls
Parasite and epiphyte gallery?
Insect gall gallery?