Physiology of Mosses
Complicated sponges with dynamic responses to water!
In my postdoctoral research (Stanton Lab, University of Minnesota Twin Cities), I am studying how moss morphology impacts water absorption, movement, and bioactivity following drought (desiccation). These moss traits, or "water functional traits" make mosses what I like to call "complicated sponges".
A moss cushion moves and holds water externally, in the capillary spaces between shoots.
Shoots also hold water internally. All species can move water passively between cells in channels called aquaporins.
Most species absorb water through all surfaces (no roots needed) and are short enough for diffusion to move water through their entire plant body.
Grand Canyon soil moss
Two dry shoots, 20x
Leaf cross section, big papillae!
Grand Canyon soil moss
Consequently, moss leaves and shoots don't need the complexities of pores (stomata) or internal vessels (xylem and phloem) of ferns and seed plants to pull water up from their roots into stems and leaves.
However, several tall (> 5-10 cm) moss species evolved simple tube-like cells (hydroids & leptoids) in their stems & leaves, which have been shown to internally move water and dissolved sugars (see Huttunen et al. 2018).