Australia: The Land Where Time Began

A biography of the Australian continent 

Parasitic Plants in the Kwongan Sandplain Flora

There are an unusually high numbers of parasitic plants in the Kwongan flora, with 10 of the 14 families that occur globally being found in the Kwongan flora and the flora of the similar region of southwest South Africa. There are 161 species in the Kwongan flora, 75 % being endemic to the region, with 4 genera that are endemic.

In hemiparasites, the root haustoria are on long hairless lateral branches. Once the haustoria is attached, tracheids in the parasitic root fuse to the xylem of the host root. The West Australian Christmas tree, Nuytsia floribunda, is a large tree with a large lignotuber, but its parasitic roots attach to any roots they encounter, even the small ones of grasses and herbs. The haustoria find the roots of other plants by being chemotropic, being attracted to any root that exudes polysaccharides. These are intended to attract the microorganisms that are beneficial to the roots exuding the substances.

There are fewer stem parasites, all being mistletoes. Amyema linophyllum, found on casuarinas, is species specific, as is A. miquelii on eucalypts and Viscum continuum, on acacias. It has been found that on Casuarina obesa, Amyema linophyllum transpires at a higher rate than the host tree, though its assimilation rate is similar, making it less efficient than the the host.

Sources & Further reading

1. Mary E. White, Earth Alive, From Microbes to a Living Planet, Rosenberg Publishing Pty. Ltd., 2003