Imhof, S. (1999):

Subterranean structures and mycorrhiza of the achlorophyllous Burmannia tenella Bentham (Burmanniaceae)

Can. J. Bot. 77: 637-643.

Abstract:

Plants of the myco-heterotrophic Burmannia tenella Benth. form star-shaped root systems consisting of 0.7 - 2 mm thick, succulent, brittle roots, reaching lengths of up to 3 cm. In cross section the roots consist of an epidermis, about 10 layers of parenchymatous cortex cells, an endodermis with u-shaped secondary cell wall depositions and a very reduced central cylinder with two to five central xylem elements and two opposite phloem strands, surrounded by a pericycle of relatively large cells.
Based on the thick, aseptate, intracellularly coiled hyphae, arbuscules, and the frequent vesicles, the fungal association of B. tenella is considered to be a Paris-type arbuscular mycorrhiza. The morphological and anatomical structures of the root are discussed in the context of the mycorrhizal dependency of B. tenella.
In some root samples, a second fungus with septate hyphae colonized the cortex intracellularly. This fungus restricts the spread of the aseptate symbiont without causing morphological changes to the cortex cells.

Key words: Burmanniaceae, root morphology, root anatomy, arbuscular mycorrhiza, myco-heterotrophy, neotropical.