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Euliss, AC; Fisk, MC; McCleneghan, SC; Neufeld, HS. 2007. Allocation and morphological responses to resource manipulations are unlikely to mitigate shade intolerance in Houstonia montana, a rare southern Appalachian herb. CANADIAN JOURNAL OF BOTANY-REVUE CANADIENNE DE BOTANIQUE. 85(10):976-985. Address: Fisk, MC, Appalachian State Univ, Dept Biol, Boone, NC 28608
High light requirements limit the distribution of several rare plant species endemic to the southern Appalachian region. We studied the influence of light and nitrogen availability on carbon allocation and morphology in one of these species, Houstonia montana Small. Insights into growth and nutrition of H. montana are needed for predicting how it will respond to ongoing changes in its environment associated with atmospheric nitrogen deposition and resulting from succession and (or) management of grassy-bald habitats in which it occurs. We hypothesized that low light constrains belowground allocation, and that elevated N availability reduces limitations to aboveground growth at low light. We tested growth and mycorrhizal colonization of H. montana in response to interactions of light and N availability in a greenhouse experiment. Shade reduced plant biomass, root:shoot ratios, and mycorrhizal colonization, and increased specific leaf area (area/mass). Elevated N reduced root:shoot ratios and mycorrhizal colonization. Under low light, N addition increased specific root length (length/mass) and foliar chlorophyll. We found support for the hypotheses that low light and high N reduce belowground allocation in H. montana. However, we did not find that high N significantly alleviates limitation to plant growth in the shade, despite changes in allocation, morphology, and chemistry that were consistent with more efficient use of C for aboveground growth. Thus, variation in the soil N availability is unlikely to have a marked effect on the ability of H. montana to tolerate shade in its native habitat.
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