PARENT SESSION
Poster Session 38: Mutualism / Parasitism
Thursday, August 11, 5:00 PM - 6:30 PM, Exhibit Hall 220 A-E, Level 2, Palais des congrès de Montréal
Impact of eastern dwarf mistletoe infection (Arceuthobium pusillum) on the needles of red (Picea rubens) and white spruce (P. glauca): Photosynthesis, biochemistry and morphology.
Reblin, Jaret*,1, Logan, Barry1, Tissue, David 2, 1 Bowdoin College, Brunswick, Maine, USA2 Texas Tech University, Lubbock, Texas, USA
ABSTRACT- Eastern dwarf mistletoe (Arceuthobium pusillum) is a hemiparasitic angiosperm that infects white (Picea glauca), black (P. mariana) and red spruce (P. rubens) in northeastern North America. Curiously, the effects of infection differ between red and white spruce where white spruce suffers greater infection induced mortality. In the present study, we sought to determine the role that host-parasite carbon exchange dynamics may play in observed differences in infection-induced host tree injury. We found that eastern dwarf mistletoe was a sink for host photosynthate in red and white spruce. However, needle non-structural carbohydrate contents (TNC) were unaltered by infection despite a lack of adjustment in needle source capacities to accommodate the added demands of the parasitic sink in either host species. Among the measurements we performed, the most obvious effect was a reduction in needle size distal to infections. The magnitude of this effect was greater in white spruce and could suggest that carbon was less locally available to support needle growth in this species. Red spruce needles had higher TNC levels despite having lower overall photosynthetic capacities, suggesting that red spruce may be more sink limited and therefore be better able to satisfy the added sink demands of the parasitic infection. However, if carbon availability limits the growth of the mistletoe, one may expect that the extent of the parasitic infection would be greater red spruce as mistletoe infecting red spruce had larger TNC pools. Yet in the field, the extent of infection is greater in white spruce. Collectively these results suggest a minimal influence of the mistletoe infection on the total carbon sink strength of the host tree in red and white spruce and that needle carbon availability does not drive the differences in the susceptibilities of the two host species to mistletoe infection.
Key words: carbon nutrition, mistletoe-host interaction, parasitic angiosperm, source-sink balance