Some of the epigean roots are found to contain an endophytic blue-green alga, Anabaena cycadearum; others are free of algae but are later invaded. Normal roots and algal-free roots possess a diarch protostele; algal-infected roots have a triarch protostele. The normal root has an epidermis which in the other roots is sloughed off and replaced by a leathery phelloderm. The algal-infected root contains in the mid-cortex a wide area filled with algal cells and spanned at infrequent intervals by starch-free layer, radially elongated cortical cells. The algal-free root contains a starch-free layer of cells in the mid-cortex which are believed to elongate radially after algal penetration has taken place. The elongate cells are high in sulfhydryl protein content and contain conspicuous globules of acidic lipids. The similarity between the elongate cortical cells and the algal cells in their preferential uptake of Bennett's red sulfhydryl reagent and in the retention of safranin red when counterstaining points strongly to a definite chemical similarity between these host cells and the endophytic alga.
Proceedings of the Iowa Academy of Science
©1960 Iowa Academy of Science, Inc.
"Histological and Histochemical Study of the Roots of Zamia floridana and the Endophytic Alga Contained In Them,"
Proceedings of the Iowa Academy of Science, 67(1), 133-138.
Available at: https://scholarworks.uni.edu/pias/vol67/iss1/21