Light on hemiparasitic plants impacts on their hosts

Although parasitic plant–host associations occur in an ever-changing light environment, there is a poor understanding of how light influences the impact of the parasite on the host plant.

Cassytha pubescens R.Br., parasitising Brachyloma daphnoides (Sm.) Benth., Black Mountain, Canberra, ACT. Photo: Donald Hobern / Flick

Cirocco et al. hypothesize that in low versus high light, as photosynthesis of the hemiparasite declines its dependency on host carbon increases so host growth is more affected. They reveal this was not the case. The Australian native hemiparasite Cassytha pubescens significantly reduces total biomass of the introduced (Ulex europaeus) but not native (Leptospermum myrsinoides) host, regardless of growth light conditions. They conclude that the strong effect of this native parasite on growth of the introduced host will be similar in areas of both low and high light availability in the field.