Variation in leaf pubescence of plants and its functional effects along elevational gradients

Abstract

Variation in leaf pubescence of plants and its functional effects along elevational gradients.

It  has  been  shown  that  on elevational  gradients  and  contrasting  elevations  plant  species  may  modify  external  structures  like  foliar  size,  stomatal  density  and  leaf thickness, mitigating the effect of adverse climatic conditions. Although the decrease in size is one of the most conspicuous responses to harsh environmental conditions, other traits such as foliar pubescence, may also contribute to increase plant species resistance to climatic stress. Foliar pubescence constitute an epidermal modification, and may vary in longitude and density with altitude, ameliorating the negative effects of climatic extremes on physiological status and growth. In the present review, I discuss the functional role of pubescence in (1) modulating incident radiation, (2) water economy, and (3) gas exchange, along an elevational gradient. Although most species may modify leaf  pubescence  to  decouple  their  photosynthetic  machinery  from  harsh  environment,  trade-offs  could  restrict  maximum  physiological efficiency. Thus, the presence of pubescence will have a positive effect on plant performance if the net cost-benefit balance, as measured in physiological and reproductive terms, is positive.