XVI International Botanical Congess
Most root hemiparasites differ obviously from mistletoes in possessing extensive root systems, exploiting many rather than a single host and carrying the potential for uptake of water and nutrients from soil independently of haustorial contacts with hosts. However, both classes of parasites extract organic and inorganic nutrients from xylem streams of hosts by means of apoplastic or symplastic transfer mechanisms. In either case, water relations of the parasite engineer flow more or less consistently in favour of the parasite and sometimes resulting in poorer water use efficiencies than in host(s). Case studies of typical root hemiparasites (Olax, Santalum) and mistletoes (Amyema) will be presented to explore how subtle differences in strategies of functioning in each class impact upon patterns of uptake, partitioning and utilisation of water, nitrogen and other nutrients and relative extents of autotrophic and heterotrophic inputs of carbon by the parasite. Likely effects of parasitism on growth and functioning of hosts will also be considered.