|Paul Jr, Rex|
Submitted to: International Journal of Plant Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/17/2002
Publication Date: 11/8/2003
Citation: Czarnota, M.A., Paul Jr, R.N., Duke, S.O., Weston, L.A. 2003. Anatomy of sorgoleone-secreting root hairs of sorghum species. International Journal of Plant Science. 164:861-866. Interpretive Summary: Several sorghum species produce a natural herbicide called sorgoleone. If crops, such as grain sorghum, could produce more of this compound, the use of synthetic herbicides could be greatly reduced in such crops. In this paper, research is described in which it was found that sorgoleone is produced only by root hairs. The process of secretion of this compound from root hairs is viewed at the electron microscope level.
Technical Abstract: Johnsongrass (Sorghum halepense (L.) Pers.) and SX-17 (Sorghum bicolor x Sorghum sudanese) were investigated microscopically to specifically identify the location of root exudate production. Light, cryo-scanning electron, and transmission electron microscopy were used to locate the area of exudate secretion. As previously reported in the literature, light micrographs indicated that the exudate was being produced by the root hairs. Scanning electron microscopy supported this conclusion. Transmission electron microscopy studies of root hairs support the view that root exudates are manufactured in the cytoplasmically dense root hair cell in association with golgi bodies and endoplasmic reticula. Ultrastructure studies indicated that small globules of cytoplasmic exudate are deposited between the cell wall and plasma membrane, where they coalesce into larger globules that pass through the cell wall to form droplets at the tip of root hairs. This process is analogous to the exudation of secondary products by secretory trichomes.