MONSON, R.K.*; LIPSON, D.A.; ROSENSTIEL, T.N.; FORBIS, T.A.; Univ. of Colorado, Boulder; San Diego State Univ.; Univ. of Colorado, Boulder; Univ. of Colorado, Boulder: Carbon and Nitrogen Storage by Alpine Herbs

Alpine plants have limited seasonal access to the resources they require for growth and persistence. Resource storage is commonly observed as a means to bridge the gap between the time when resources become available and the time when they are most required. Resource storage comes at cost as stored resources cannot simultaneously be used to support growth or maintenance, and as there is a cost to construct storage tissues. Our observations have shown that nitrogen stored during the winter, primarily as the free amino acids arginine and delta-acetylornithine, are mobilized in the early spring to support approximately 60% of the growth of the alpine herb Bistorta bistortoides. Plants of B. bistortoides adjust their reliance on stored nitrogen depending on availability. An increase in reliance on stored nitrogen is accompanied with a decrease in soil nitrogen uptake, minimizing the opportunity cost of obtaining nitrogen. Adjustments in storage capacity are made through changes in nitrogen concentration per cell, rather than through the addition of new cells. In storage tissues, the sucrose concentration per cell decreases in response to increased nitrogen storage, reflecting the increased carbon costs of nitrogen storage. Seasonal nonstructural carbohydrate storage is high in alpine species compared to non-alpine species. Several alpine taxa exhibit high storage rates of cyclic and/or acyclic polyols. The capacity to store polyols has a clear phylogenetic component and those taxa that store polyols exhibit higher drought tolerance in dry alpine habitats. The use of carbohydrate compounds as an adaptation to drought, as well as storage, reduces the opportunity cost of the compound compared to if it were used only for either function alone.