R oot tubercles in apostasiad orchids

Tubercles are swollen, stalked, warty branches arising from the main elongated roots of species in the terrestrial orchid genus Apostasia (subfamily Apostasioideae). Generalized anatomy resembles that of the main roots, except tubercles lack a velamen and conductive strands are few. There are multinucleate cortical cells, and stomata occur in the epidermis. Pores of stomata appear to be permanently open and thus may enhance the interchange of gases between root tissues and soil under the moist conditions in which apostasias grow. Multicellular warts seem to function as holdfasts and are points of entry for mycorrhizal fungi.