Epiphytes: photosynthesis, water balance and nutrients

Abstract

Epiphytes are plants adapted to living in the canopy and can be classified as facultative, hemiepiphytes or obligatory depending n the period spent in the canopy and if the species also occur as soil-rooted plants. Epiphytes are subjected to same environmental pressures as soil-rooted plants, such as demand water, light and nutrients, although environmental fluctuation tend to be more frequent. Epiphytes do not show any exclusive photosynthesis pathway, even though CAM is relatively common within this group, specially among orchids. In general, epiphytes are slow growing plants with high water use efficiency. This trait can be less competitive in environments with more favorable conditions where competition is more pronounced. Yet, among other epiphytes the vegetative growth phase coincides with the rain season. These plants can spend as much as 1.000g water per gram of organic matter produced, whereas among plants with high water use efficiency typical rates are 100:1. This variety of strategies demonstrates that, as in soil-rooted plants, a more parsimonious use of water does not necessarily represent the best mechanism to compromise water economy and growth.