(American Journal of Botany. ;90:0.)
© Botanical Society of America, Inc.
Heliotropism and pollen performance
Galen and Stanton continue on-going work on the adaptive significance of heliotropism in alpine buttercups in a study in which they experimentally restrained flowers from tracking the sun's rays over the course of the day. Flowers that were prevented from tracking the sun produce pollen that does not perform as well as that produced by unrestrained flowers and produce stigmas that are less favorable for pollen tube growth than the stigmas on unrestrained flowers. The authors were able to conclude that the higher pollen tube germination in sun-tracking flowers was likely due to the warmer microenvironment provided during pollen tube growth.Their paper represents one of the very few demonstrations of apparent environmental effects on pollen performance under field conditions.
(see p. 724)
Miller and Diggle describe how variation in andromonoecy arises in four closely related members of Solanum section Lasiocarpa. Andromonoecy is a sexual system occurring in approximately 4000 species of flowering plants representing 32 families in which both hermaphroditic and staminate flowers occur on the same individual. Beginning from work showing that fruit-bearing plants produce a greater proportion of staminate flowers than genetically identical plants that are prevented from producing fruit, the authors distinguish key factors that influence the very plastic expression of this sexual system and suggest important avenues for future research on the development and evolutionary basis of this mating system.
(see p. 707)
Research on seed fates in prairie habitats is important for efforts toward restoration of our native prairies. Clark and Wilson set out to determine simultaneously the three possible fates (persistence, germination, and death) and factors affecting death awaiting seeds after dispersal for four species, including native and nonnative herbs and grasses, in a native upland prairie in western Oregon. Mortality was between 44 and 80% for all four species, and the authors present useful data on mortality factors.
(see p. 730)
Cladium (sawgrass) is an important species, especially in the Florida Everglades, where environmental changes are causing the displacement of Cladium communities by Typha (cattail) communities. Lissner et al. go a long way toward providing a model for why these changes are occurring. Cladium was cultured in an environment where redox potential (Eh) and phosphorus availability were precisely controlled. Environmental control of the root environment in whole-plant studies is challenging, and one reviewer calls the design used in this study "state of the art."
(see p. 736)
