- Key People:
- William Starling Sullivant
Bryophytes generate their nutrient materials through the photosynthetic activity of the chlorophyll pigments in the chloroplasts. In addition, most bryophytes absorb water and dissolved minerals over the surface of the gametophore. Water retention at the surface is assisted by the shape and overlapping of leaves, by an abundance of rhizoids, or by capillary spaces among these structures. Water loss through evaporation is rapid in most bryophytes.
A few bryophytes possess elaborate internal conducting systems (see below Form and function) that transfer water or manufactured nutrients through the gametophore, but most conduction is over the gametophore surface. In most mosses, water and nutrient transfer from the gametophore to the developing sporangium takes place along the seta and also via an internal conducting system. A protective cuticle covers the seta, reducing water loss. The calyptra that covers the developing sporangium prevents water loss in this fragile immature structure. In liverworts the sporangium remains close to the gametophore until it is mature; thus, a conducting system is not formed in the seta. In most hornworts there is also an internal conducting system within the developing horn-shaped sporangium. The internal movement of fluid in all parts of the bryophyte is extremely slow. Storage products include starch and lipids.