Home Mission 2007 Team Members Research Sources Progress Journal	Factors for their success - an analysis on their physiology There are several factors responsibles for the success of mosses and lichens in Alaskan region. The two groups are remarkably similar in attributes beneficial in severe environments. Both tend to occupy and create relatively favourable microenvironments. Many species exhibit a broad response of net assimilation rate to temperature, with maxima at 10-15oC but with positive net assimilation and dark respiration continuing at or below 0oC. Light compensation and saturation intensities are typically lower in mosses and lichens than in vascular plants, and compensation levels decrease with temperature permitting positive net assimilation under cool, low-light conditions. Moreover, most species have little access to soil moisture and lack an effective cuticle; this enables them to absorb water through much of their surface but results in rapid water loss under drying conditions. Yet, though the plants become inactive when dry, they resume normal metabolism rapidly on remoistening. Thus, mosses and lichens are thus adapted to switching rapidly between periods of metabolic activity and rest, utilizing favourable conditions whenever they occur. This may be facilitated by micromorphological features thought to facilitate simultaneous uptake by moss leaves of both water and carbon dioxide. They also resist frost very well by conferring tolerance of cytoplasmic dehydration resulting from extracellullar ice formation.
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