Poster: Root Biology

Abs # 535: Lateral root development and the effect of exogenous auxin in Ceratopteris richardii

Presenter:	Hou, Guichuan , ghou@noble.org
Authors	Hou, Guichuan  (A)   Hill, Jeffrey P (B)   Blancaflor, Elison B (A)
Affiliations:	(A): Noble Foundation (B): Idaho State University
Web Site:	http://www.noble.org/PlantBio/Blancaflor/Index.htm

In the homosporous fern Ceratopteris richardii, lateral roots arising from shoot-borne roots originate from the endodermis adjacent to xylem poles. The number of lateral roots increases with increasing parental root position along the shoot in early sporophyte ontogeny, showing an additional feature of heteroblastic root development in this species. A detailed study of the fifth root produced by young sporophytes shows that one lateral root mother cell (LRMC) develops in each two of three successive merophytes. As a result, lateral roots emerge alternately from opposite positions on a parental root. From LRMC initiation to lateral root emergence, three major developmental stages are identified based on anatomical criteria. The addition of auxins (indole-3-acetic acid and indole-3-butyric acid) to the growth media at varying concentrations did not induce additional lateral root formation, but exogenous auxin inhibited parental root growth rate. Application of the auxin-transport inhibitor naphthylphthalamic acid also did not change the lateral root developmental pattern in this fern. These studies suggest that the pattern of lateral root formation does not depend on root growth rate per se. The insensitivity of lateral root formation to exogenous auxins in C. richardii is reminiscent of the acropetal lateral root population reported for certain species in flowering plants. It may also argue for different mechanisms controlling lateral root development in non-seed vascular plants compared to angiosperms, considering the long and independent evolutionary history of the two groups.