Do antheridiogens act via gametophyte size? A study of Woodwardia radicans (Blechnaceae)

Abstract

For many plants, sex is not fixed by genotype but determined by environmental conditions during development. In homosporous pteridophytes, sex is environmentally determined by the presence or absence of antheridiogens, maleness-inducing pheromones. It has been proposed that antheridiogens primarily reduce growth rate, with small gametophyte size responsible for maleness. To test this hypothesis, the effects of antheridiogen and intergametophytic competition on gender expression and gametophyte size were studied in a culture experiment with Woodwardia radicans. We found that (1) antheridiogen inhibited growth of gametophytes; and (2) slow growth favored maleness, whereas fast growth favored femaleness, irrespective of the presence or absence of antheridiogen. Both conclusions are consistent with the hypothesis that, in W. radicans, antheridiogen effect is mediated by size. They also agree with the "size-advantage" hypothesis in which energetic limitations associated with relatively small individual size impose a less severe limitation for male reproductive success than for female reproductive success. The results are also discussed with regard to a genetic sex-determining pathway that has recently been identified.

Environmental sex determination in ferns: effects of nutrient availability and individual density in Woodwardia radicans

“…In males, the position of antheridia is variable. In experimental cultures, female and bisexual gametophytes release an antheridiogen that inhibits vegetative growth and induces antheridium production in asexual gametophytes (Quintanilla et al. 2007b).…”

“…Secondly, is the threshold size for sex switch fixed or variable according to environmental conditions as shown for angiosperms (Bierzychudek 1984a)? Preliminary evidence in W. radicans also indicates that the threshold for female expression is variable (Quintanilla et al. 2007b).…”

Antheridiogen concentration and spore size predict gametophyte size inCeratopteris richardii

“…A CE here also affects the growth of male gametophytes in a dosage-dependent manner. Quintanilla et al (2007) and Stevens and Werth (1999) reported dosage-dependent activity of antheridiogens in Woodwardia radicans (L.) J. Sm. and Onoclea sensibilis L., respectively.…”

“…Because of this, the potential role of nutrients in modifying this hormonally determined gender system has been suggested (Haig and Westoby 1988;Korpelainen 1994;Quintanilla et al 2007;Ayrapetov and Ganger 2009). A CE may act directly through the signal transduction system to suppress female genes or, alternatively, A CE may slow down growth and development.…”

Germination and reproductive biology in salty conditions of Asplenium marinum (Aspleniaceae), a European coastal fern

“…It is clear that in A. marinum, increased salinity affects development of gametangia, most negatively the appearance of archegonia, but by higher salt concentrations also preventing antheridia formation. Reduced production of antheridia when salt is present may be due to the overall growth restriction by higher salinity, given that slow growth generally favours maleness in ferns (Quintanilla et al, 2007). Nevertheless, when ungerminated spores, which have been kept at high salinity concentration (3.26%-salt medium) that prevents germination, were transplanted to control culture media, i.e.…”