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

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.

Dan Lewis. 30 December 1910 — 30 September 2009

Dan Lewis is best known for his work on plant breeding systems. Self-incompatibility is common in hermaphroditic plants as a mechanism that prevents inbreeding; it may be determined by genes expressed in the haploid gametes (gametophytic) or by those expressed in the diploid tissue that gives rise to gametes (sporophytic). At different times in his career, Lewis contributed to a better understanding of both these systems, but it was his work on the gametophytic system in the evening primrose, Oenothera organensis , that broke new ground and enabled him to predict a molecular recognition between different proteins produced in the pollen and style; these proteins were encoded by tightly linked genes at a complex self-incompatibility ( S ) locus. Modern molecular techniques have since confirmed these predictions and revealed the actual nature of the proteins and their interactions. The research began as part of a programme of breeding plants of horticultural and agricultural importance while working at the John Innes Institute, the foremost place to study genetics in the UK at that time. The Institution had William Bateson (FRS 1894) as its first director, followed by Sir Daniel Hall (FRS 1909), who in turn was succeeded in 1939 by Cyril Darlington (FRS 1941). To begin your career there in the 1930s was almost guaranteed to lead to scientific success.