title: Developing sporophytes transition from an inducible to a constitutive ecological strategy of desiccation tolerance in the moss Aloina ambigua: effects of desiccation on fitness.
abstract: OBJECTIVE
  Two ecological strategies of desiccation tolerance exist in plants, constitutive and inducible. Because of difficulties in culturing sporophytes, very little is known about desiccation tolerance in this generation and how desiccation affects sexual fitness.
  
  
  METHODS
  Cultured sporophytes and vegetative shoots from a single genotype of the moss Aloina ambigua raised in the laboratory were tested for their strategy of desiccation tolerance by desiccating the shoot-sporophyte complex and vegetative shoots at different intensities, and comparing outcomes with those of undried shoot-sporophyte complexes and vegetative shoots. By using a dehardened clonal line, the effects of field, age and genetic variance among plants were removed.
  
  
  RESULTS
  The gametophyte and embryonic sporophyte were found to employ a predominantly inducible strategy of desiccation tolerance, while the post-embryonic sporophyte was found to employ a moderately constitutive strategy of desiccation tolerance. Further, desiccation reduced sporophyte fitness, as measured by sporophyte mass, seta length and capsule size. However, the effects of desiccation on sporophyte fitness were reduced if the stress occurred during embryonic development as opposed to postembryonic desiccation.
  
  
  CONCLUSIONS
  The effects of desiccation on dehardened sporophytes of a bryophyte are shown for the first time. The transition from one desiccation tolerance strategy to the other in a single structure or generation is shown for only the second time in plants and for the first time in bryophytes. Finding degrees of inducible strategies of desiccation tolerance in different life phases prompts the formulation of a continuum hypothesis of ecological desiccation tolerance in mosses, where desiccation tolerance is not an either/or phenomenon, but varies in degree along a gradient of ecological inducibility.
authors.affiliation: School of Life Sciences, University of Nevada, 4505 Maryland Parkway, Las Vegas, NV 89154-4004, USA and Missouri Botanical Garden, P.O. Box 299, St Louis, MO 63166-0299, USA LRS@UNLV.nevada.edu.
authors.forename: Lloyd R
authors.initials: LR
authors.lastname: Stark
authors.affiliation: School of Life Sciences, University of Nevada, 4505 Maryland Parkway, Las Vegas, NV 89154-4004, USA and Missouri Botanical Garden, P.O. Box 299, St Louis, MO 63166-0299, USA.
authors.forename: John C
authors.initials: JC
authors.lastname: Brinda
mesh_terms: D019068:Bryopsida / Q000235:genetics* / Q000254:growth & development*; D003890:Desiccation; D056084:Genetic Fitness; D055993:Germ Cells, Plant / Q000254:growth & development; D010641:Phenotype; D018520:Plant Shoots / Q000254:growth & development
keywords: Aloina ambigua; Bryophyte; Pottiaceae; chlorosis; constitutive desiccation tolerance; dehardening; inducible desiccation tolerance; moss; phenology; rate of desiccation; seta elongation; sporophyte embryo; sporophyte fitness