Host Associations of the Introduced Annual Root Hemiparasite Parentucellia viscosa in Agricultural and Bushland Settings in Western Australia

• Published in: Annals of botany 2000-02, Vol.85 (2), p.203-213
• Main Authors: PATE, J.S., BELL, T.L.
• Format: Article
• Language: English
• Subjects: 15N and13C signatures; amino acid composition; Amino acids; growth benefit; Hemiparasites; host range; Native species; Parasite hosts; Parasites; Parasitism; Parentucellia viscosa; Parentucellia viscosa, root hemiparasite, host range, growth benefit,15N and13C signatures, amino acid composition; Plant growth; Plant roots; Plants; root hemiparasite; Taxa
• ISSN: 0305-7364; 1095-8290
• DOI: 10.1006/anbo.1999.1018

Populations of the introduced annual root hemiparasite, Parentucellia viscosa (L.) Caruel (Scrophulariaceae), were examined in habitats where introduced, mixed introduced plus native, or solely native species provided potential hosts. Presence of haustoria on host roots confirmed parasitism of 17 introduced and ten native taxa across the sites investigated. Paired plots, one with all hosts removed early in the season, the other left intact, showed overall increases in shoot dry matter of the parasites over 3 months of growth. Results indicated a substantial growth benefit to the parasite from continued access to introduced and indigenous plant species, although the parasite continued growing to a limited extent after removal of hosts. Carbon isotope discrimination values (δ13C) were consistently more negative for parasites than for associated hosts, and more negative for parasites in plots containing hosts than in plots from which hosts had been removed. Values for δ15N discrimination of shoot dry matter of parasites lay mostly within the range of those of hosts. The δ13C data suggested poorer water use efficiency of parasite than hosts, while corresponding δ15N data indicated particularly effective uptake of N-containing compounds from the N2-fixing host, Lotus angustissimus. Where the parasite had access to only one or a few closely related hosts, the composition of the soluble amino fraction of its leaves generally matched that of foliage of host(s). However, in some instances the parasite accumulated certain amino compounds to a much greater or lesser relative extent than did its partner host(s). Where many hosts were being exploited, compositional features of the soluble amino fraction of the parasite suggested major access to nitrogenous solutes from specific hosts. Data are discussed in relation to previously published observations on haustorial-derived benefits indicated for other species of root hemiparasites.