Imhof, S. & Sainge, M. N. (2008):

Ontogeny of the mycoheterotrophic species Afrothismia hydra (Burmanniaceae)

Bot. J. Linn. Soc. 157: 31-36

Abstract:

The complete ontogeny of the mycoheterotrophic Afrothismia hydra (Burmanniaceae) from seed to seed dispersal is presented. The, oblong-ovoidal seeds are up to 0.7 mm long. They germinate with root tissue only, disrupting the seed coat and developing a primary ovoid root tubercle. At the proximal end of the tubercle a second tubercle arises, and further root initials indicate the sequential growth of more root tubercles with filiform extensions resulting in a small root aggregate. The seed coat often remains attached to this structure. When the root aggregate enlarges a central axis to which all roots are connected becomes visible. This axis has a growth pole where new root tubercles arise. The same growth pole will later develop into a stem with scale leaves finally terminating in a flower. Flowers develop sympodially when the mature plant is only several centimetres long. After anthesis, the corolla tube disintegrates, leaving a pyxidium which opens by means of an peculiar elongating placenta, here called ‘placentophore’. The placentophore elevates the placenta with attached seeds above the flowering level and is interpreted as an adaptation to ombrohydrochory. The reduction of hypocotyl, cotyledon and primary shoot is discussed with regard to the classical germination concepts of monocotyledons , and with mycoheterotrophic dicotyledons.