User:Frida Rosengren/sandbox
Dvärghannar
[edit]Mossdvärghannar kommer från hansporer som landar och gror på honskottet där de inte blir mer än några få millimeter stora. Hos visMoss dwarf males (also known as nannandry or phyllodioicy) originate from wind-dispersed male spores that settle and germinate on the female shoot where their growth is restricted to a few millimeters. In some species, dwarfness is genetically determined in that all male spores become dwarf.[1] More often however, it is environmentally determined in that male spores that land on a female become dwarf, while those that land elsewhere develop into large, female-sized males.[1][2][3][4] In the latter case, dwarf males that are transplanted from females to another substrate develop into large shoots, suggesting that the females emit a substance which inhibits the growth of germinating males and possibly also quickens their onset of sexual maturation.[3][4] The nature of such a substance is unknown, but the phytohormone auxin may be involved[1]
Having the males growing as dwarfs on the female is expected to increase the fertilization efficiency by minimizing the distance between male and female reproductive organs. Accordingly, it has been observed that fertilization frequency is positively associated with the presence of dwarf males in several phyllodioicous species.[5][6]
Dwarf males occur in several unrelated lineages[6][7] and is showing to be more common than previously thought.[6] For example, it is estimated that between one quarter and half of all dioicous pleurocarps have dwarf males.[6]
- ^ a b c Une, Kouji (1985). "Sexual dimorphism in the Japanese species of Macromitrium Brid.(Musci: Orthotrichaceae)". The journal of the Hattori Botanical Laboratory devoted to bryology and lichenology. 59: 487–513.
- ^ Blackstock, T. H. (1987). "The male gametophores of Leucobryum glaucum (Hedw.) Ångstr. and L. juniperoideum (Brid.) C. Muell. in two Welsh woodlands". Journal of bryology. 14 (3): 535–541.
- ^ a b Loveland, Hugh Frank (1956). Sexual dimorphism in the moss genus Dicranum Hedw. (Dissertation). University of Michigan.
{{cite book}}: Cite has empty unknown parameter:|publication year=(help) - ^ a b Wallace, M. H. (1970). Developmental morphology and sexual dimorphism in Homalothecium megaptilum (Sull.) Robins. (Dissertation). Washington State University.
- ^ Sagmo Solli, I. M.; Söderström, Lars; Bakken, Solveig; Flatberg, Kjell Ivar; Pedersen, Bård (1998). "Studies of fertility of Dicranum majus in two populations with contrasted sporophyte production". Journal of Bryology. 22 (1): 3–8. doi:10.1179/jbr.2000.22.1.3.
- ^ a b c d Hedenäs, Lars; Bisang, Irene (2011). "The overlooked dwarf males in mosses—unique among green land plants". Perspectives in Plant Ecology, Evolution and Systematics. 13 (2): 121–135. doi:10.1016/j.ppees.2011.03.001.
- ^ Ramsay, Helen P.; Berrie, G. K. (1982). "Sex determination in bryophytes". Journal of the Hattori Botanical Laboratory. 52: 255–274.