Mechanism of Spontaneous Autogamy in the Allogamous Lepidopteran Orchid Gymnadenia Conopsea (L.) R. Br. (Orchidaceae)

Abstract

Studies of plant breeding systems are particularly important when they involve facultative processes, which can be overlooked in natural conditions. This especially applies to species that are considered allogamous, due to their pollination syndrome and floral architecture. We examined the potential level and factors enabling or limiting spontaneous autogamy in three populations of the lepidopteran orchid Gymnadenia conopsea. Using a bagging experiment, we noted the stages of the anther thecae and the positions of the pollinaria at the five phenological stages of the flower, as well as the quantity of autogamously set fruits and the number of properly formed seeds. In the studied populations, autogamy represents an accidental character, with a maximum of 3.3% of fruits set spontaneously per analysed sample in a given population, and with seed numbers ranging from 29 to 354. This process is an environmentally dependent co-product of the mechanisms that enable a position appropriate for touching the stigma (bending of the caudicle) and increase male fitness (disintegration of the massulae), preceded by the gradual opening of the anther chambers. Autopollination of G. conopsea may occur in the flowers at various flowering stages (excluding the beginning of anthesis) at each position on the inflorescence. K Ke ey y w wo or rd ds s: : Anther thecae, bending movement, dehydration, disintegrated pollinium.

The Ability of Spontaneous Autogamy in Four Orchid Species: Cephalanthera Rubra, Neottia Ovata, Gymnadenia Conopsea, and Platanthera Bifolia

“…In the case of G. conopsea, the mean seed number per capsule was the same as that in naturally developed fruits in the ZAB2 population observed in 2013 (Tałałaj and Skierczyński, 2015). A similar level of 2044 seeds was also obtained after natural pollination by Salisbury (1942) and 1675 seeds by Vakhrameeva et al (2008).…”

“…To verify the mechanism and time of spontaneous autogamy in this species, we carried out further research in three populations from northeast Poland in 2013 (Tałałaj and Skierczyński, 2015). Using a bagging experiment, we noted the stages of the anther thecae and the positions of the pollinaria at five phenological stages of the flower.…”

“…Self-pollination may occur in flowers at each position on the inflorescence and at various flowering stages except for the beginning of anthesis. This phenomenon is caused by the bending of the caudicle and massulae disintegration, which is preceded by the gradual opening of the anther chamber (Tałałaj and Skierczyński, 2015).…”

Spontaneous caudicle reconfiguration in Dactylorhiza fuchsii: A new self-pollination mechanism for Orchideae

“…For the particular pollinarium stages with the pollinia hanging free outside the thecae, massula disintegration was differentiated between the years, although the similar maximum fraction of approximately 0.30 records was achieved for each pollinarium stage P2, P3, P4 and P7. Whereas spatial and temporal differences in pollinium disintegration within the same flower may result from differences in the habitat humidity (Catling 1990;Peter and Johnson 2006;Tałałaj and Skierczyński 2015), we found that the habitat played a minor role in auto-pollination and fruit development of D. fuchsii.…”

“…Among these species, 5 species were identified as obligatorily autogamous and 2 species as facultatively autogamous, and for 10 species, this mechanism was recognized as accidental or questionable. This list continues to be augmented (Suetsugu 2013(Suetsugu , 2015Tałałaj and Skierczyński 2015). Accidents of caudicle bending within flowers (without data about self-fertilization) were noted in three species widely distributed in Europe in the genus Dactylorhiza: D. maculata, D. incarnata and D. majalis (Martens 1926;Groll 1965;Reinhard 1977;Dressler 1981).…”