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Aquaporins are transmembrane proteins that move water specifically and bidirection-aUy in response to internal cell signaling. With aquaporins, plant cells can control how, where, and when water moves across membranes, Thus, plants are in strong control of their environmental responses. Therefore, it seems likely that aquaporins would have a key role in water balance in xerophytic ferns, particularly in the gametophyte stage. To investigate the role of aquaporins in desiccation avoidance in xerophytic ferns gametophytes, Cheilanthes lanosa gametophytes were poisoned with micromolar mercury solutions, which block aquaporin channels, exposed to several osmolytes, and quantified the efflux of water from the cells was quantified. Results strongly suggest that aquaporins may very well play a role in water balance, but also pose some questions concerning the ability of the protonemal stage to fully manage water flow [ABSTRACT FROM AUTHOR]

Cheilanthes lanosa is a xerophytic fern that inhabits rock cliffs and crevices. Morphological features such as cuticle and trichomes assist sporophyte survival. However, the gametophyte stage appears to lack any water-saving features. Previous studies suggest that the gametophyte may balance its water through carbohydrate production and a strong internal osmotic gradient. To investigate the basis for gametophyte survival, lipids and carbohydrates were quantified using the vanillin and anthrone assays. Results suggest that lipids and carbohydrates increase in percent of total biomass (w/w) throughout development. In addition, lipid and carbohydrate content can change with varying culture conditions. Young gametophytes, with high carbohydrate and low lipid content, are relegated to substrates with a potential for a small but continuous water source. [ABSTRACT FROM AUTHOR]