Partitioning of Dry Matter and Mineral Nutrients During a Reproductive Cycle of the Mistletoe Amyema linophyllum (Fenzl.) Tieghem Parasitizing Casuarina obesa Miq.

Budgets for utilization of dry matter, nitrogen and a rangeof mineral elements were constructed for the reproductive season(September 1988–May 1989) of plants of the mistletoe Amyemalinophyllum (Loranthaceae) parasitizing the swamp she oak (Casuarinaobesa Miq.) at Gingin, W. Australia. Shed buds comprised 55%of the allotment of dry matter to reproduction, shed flowers7%, abscised perianths and styles 15%, prematurely shed fruits15%, and successfully ripened fruits a mere 12%. Commitmentto reproductive biomass peaked sharply in October, while thegenerally higher rate of allocation to vegetative biomass declinedfrom beginning to end of the 9-5 month reproductive cycle. Investmentsof dry matter in new leaves and secondary thickening of previousseason's stems were several-fold greater budget items than productionof new stems and shedding of leaves. There was no evidence ofpre-senescence retrieval of N, P, and K from leaves, and concentrationsof Ca, Mg, Na, and Cl increased steadily in dry matter withleaf age. Values for reproductive effort (RE) for dry matterand specific mineral elements were calculated as commitmentto reproduction divided by commitment to reproduction plus vegetativebiomass (? 100). Due to highly differential partitioning ofcertain elements between reproductive and vegetative parts,RE values for minerals for the reproductive season ranged widely,viz. 7% for Ca, 10% for Mn, 15% for Mg, 17% for N, 25% for Kand Zn, 26% for Cu, and 35% for P. The comparable RE for drymatter was 29%. The weight ratio for net intake of nutrientelements from the host by A. linophyllum for the reproductiveseason was 21?5:20?2:6?6:1?6:1 (N:K:Ca:Mg:P), while the meanweight ratio for the concentrations of these elements in xylem(tracheal) sap of the Casuarina host was 13?9:15?6:4?1:30:1,respectively. The data are discussed in relation to the demonstrationof a direct lumen-to-lumen tracheary continuity between hostand mistletoe in mature regions of the haustorial interface. Key words: Mistletoe, resource allocation, mineral nutrition, reproductive effort, host:parasite relationships