parasitic plants in natural ecosystems (lecture 5) Flashcards
1
Q
what makes a true parasitic plant?
A
- defined by transfer organ called a haustorium
- haustoriums rip through host roots, fusing with the host vascular system
- either xylem (usually hemiparasitic - possesses some chlorophyll), or phloem and xylem (usually holoparasitic - possess no chlorophyll)
2
Q
what is rhinanthus minor?
A
- facultative root hemiparasite
- lives in northern temperate grasslands
- can induce shifts in species communities
- suppresses grasses, promotes forbs, have been attempts to introduce to species poor communities for restoration
3
Q
how does it influence communities?
cameron et al (2005, 2009)
A
2005
- v variable effects when introducing R. minor
2009
- rock paper scissors dynamics
- prevents competitive exclusion of forbs
- manipulation of competitive hierarchies
- can reduce net ecosystem productivity though
- competes above ground and parasitises below, suppressing photosythesis to reduce above ground biomass but below ground remains
4
Q
what is the shifting cloud hypothesis in terms of rhinanthus?
cameron et al, 2009
A
- r. minor causes community to exist as a mosaic of contiguous patches in differing stages of regeneration with differing parasite densities
5
Q
what is active host choice in r minor?
gibson and watkinson, 1989
A
- evidence from other plants
- g&w found evidence for preferential host
- but study BIASED due to forbs having easier roots to find than grass
- thought they selected for forbs, assoc w/ which can be lethal for rhinanthus
- grows much better on grass, grows better without host than on certain forbs
- probably not host selective, will even attack perspex
6
Q
what is differential host resistance in rhinanthus?
cameron et al, 2007)
A
- grasses don’t have parasite defense (mostly)
- forbs can defend (mostly)
- there is a continuum though, helps explain different order of magnitudes of community response
