Best Practices for Measuring Photosynthesis at Multiple Scales

Abstract

Studies of bryophyte photosynthetic performance have generally adapted techniques developed for use in vascular plants and relied on underlying vascular plant functional models as guides. Within this context, bryophytes present intellectual and methodological challenges, but also opportunities relative to their vascular plant counterparts. For example, although the leaf is clearly a functional unit for vascular plants, the comparable bryophyte structure may or may not serve a similar purpose. Instead, shoot systems and their organization into canopies are often employed as the functional equivalent. Unfortunately, due to issues of scale and alternative functional demands on bryophyte shoots like external transport and nutrient uptake, neither the methodologies nor the underlying models that lead to an integrated understanding of photosynthesis in vascular plants apply well to bryophytes. This chapter will consider the appropriate functional units for studies of bryophyte photosynthesis and relate it to the growth form and life form literature. Methods to characterize photosynthetic "leaf" area, water content, and canopy structure will be evaluated relative to their use in characterizing rates of photosynthesis. In addition, various methods are used to study photosynthetic function and these will be considered in light of their appropriate spatial and temporal domains.