Anatomical and histochemical features of Brasenia schreberi (Cabombaceae) shoots

The present research on Brasenia schreberi, a member of the aquatic, basal angiosperm family, Cabombaceae, investigates the anatomy and histochemistry of this critically endangered plant. The shoots of B. schreberi have vertical rhizomes, horizontal rhizomes, and stolons with peduncles and leaves. Most stems typically have polysteles with bicollateral vascular bundles, each with two groups of primary xylem tracheids and primary phloem sieve tube elements, an endodermis with Casparian bands around each vascular bundle, and epidermis with glandular trichomes or "mucilaginous hairs" and discontinuous cuticle. Most stems have a protoxylem lacuna between the two regions of primary xylem and primary phloem in each bicollateral vascular bundle and extensive aerenchyma in ground tissues. Epidermal glandular trichomes are composed of two disk-like stalk cells and enlarged glandular or hair cells with storage space and mucilage, which covers the cells. The structural features of B. schreberi are generally consistent with those of other aquatic basal angiosperms and with its adaptation to an aquatic environment.