RADICLE OF ECHINOCACTUS-PLATYACANTHUS (CACTACEAE)

Radicle of mature Echinocactus platyacanthus embryo is approximately 3 20 mu m long and represents less then 1/7 of the embryonal axis length . The radicle-hypocotyl boundary can be distinguished according to the striking difference in the size and shape of cells in protoderm and p rocambium, as well as discontinuity and different number of the cell f iles in the ground meristem. The root cap is small, consists of 4 laye rs of cells covering the apex of the radicle. The upper limit of the r oot cap is approximately 100 mu m closer towards the radicle tip than the radicle-hypocotyl boundary. Ultrastructure of radicle cells showed numerous lipid bodies as is typical for other oily seeds. Protein bod ies of variable structure were also present together with other cell s tructures. Striking differences in protein body structure were found w hen protoderm and ground meristem were compared. Several small globoid crystals were present in each protein body of the protoderm, while pr otein bodies in the radicle ground meristem mostly contained one large globoid crystal. X-ray microanalysis revealed presence of P, K and Mg in all analyzed globoid crystals. Fe, Ca and Zn were detected in some of them.