Lichens were cultured by attaching a thallus fragment to a nylon monofilament loop with silicone sealer. Two effective methods for adjusting lichen mass to a standard moisture content were developed (the ‘reference-sample’ and ‘sacrificial’ methods). These corrections for moisture content allow detection of very small changes in dry mass without having to oven dry (and kill) all transplants. Average annual biomass growth rates for non-fragmenting species were typically between 5 and 30%. Annual biomass growth rates of healthy, vigorous individuals, as indicated by the 75th percentile, were mostly between 10 and 40%. Alectoria sarmentosa was prone to fragmentation despite the maintenance of healthy thalli. The other species can be ranked by biomass growth rates as follows: Evernia prunastri> Lobaria pulmonaria=Usnea longissima> Pseudocyphellaria rainierensis=Lobaria oregano.

No abstract

The response of woody plant tissues to freezing temperature has evolved into two distinct behaviors: an avoidance strategy, in which intracellular water supercools, and a freeze-tolerance strategy, where cells tolerate the loss of water to extracellular ice. Although both strategies involve extracellular ice formation, supercooling cells are thought to resist freeze-induced dehydration. Dehydrin proteins, which accumulate during cold acclimation in numerous herbaceous and woody plants, have been speculated to provide, among other things, protection from desiccative extracellular ice formation. Here we use Cornus as a model system to provide the first phylogenetic characterization of xylem freezing behavior and dehydrin-like proteins. Our data suggest that both freezing behavior and the accumulation of dehydrin-like proteins in Cornus are lineage related; supercooling and nonaccumulation of dehydrin-like proteins are ancestral within the genus. The nonsupercooling strategy evolved within the blue-or white-fruited subgroup where representative species exhibit high levels of freeze tolerance. Within the blue-or white-fruited lineage, a single origin of dehydrin-like proteins was documented and displayed a trend for size increase in molecular mass. Phylogenetic analyses revealed that an early divergent group of red-fruited supercooling dogwoods lack a similar protein. Dehydrin-like proteins were limited to neither nonsupercooling species nor to those that possess extreme freeze tolerance.Due to their sessile nature, plants have been forced to adapt to the dynamic environmental conditions that surround them. Temperature creates a selective pressure on plants growing in temperate climates and has affected their geographical distribution based upon a capacity to survive seasonal thermal fluctuations (Smithberg and Weiser, 1968;Sakai and Weiser, 1973;George et al., 1974;Becwar et al., 1981;Gusta et al., 1983). In woody plants, two distinct and fundamentally different strategies for the seasonal survival of subzero temperatures have evolved: freeze tolerance (nonsupercooling) and freeze avoidance (supercooling; Burke et al., 1976;George et al., 1982). Freezing behavior strategies employed by a woody plant vary from tissue to tissue and are species specific. For example, cortical tissues are strictly nonsupercooling; however, buds and xylem ray parenchyma may exhibit either strategy. In nonsupercooling tissues, ice formation is initiated within extracellular spaces and generates a dehydrative vapor pressure gradient between extracellular ice and intracellular water. Nonsupercooling cells readily desiccate in response to extracellular ice formation (George et al., 1982; and are capable of surviving low temperature extremes (Guy et al., 1986) due to an inherent capacity to tolerate desiccation Fujikawa et al., 1997). In supercooling tissues, ice may also initiate in extracellular spaces; however, cells are thought to resist intracellular desiccation (Burke et al., 1976;George et al., 1982;Wisniewski and Ashworth, 1985;Fujik...