The behaviour of two cell populations in the pericycle of Allium cepa, Pisum sativum, and Daucus carota during early lateral root development
1989
Lloret, P.G. | Casero, P.J. | Pulgarin, A. | Navascues, J.
The length of cells of the pericycle, endodermis and middle cortex not actively involved in lateral root primordia (LRP) development was measured in primary roots of Allium cepa, Pisum sativum and Daucus carota. The presence of two cell populations in the pericycle was demonstrated in all three species. In Allium cepa and Pisum sativum, pericyclic cells located opposite xylem poles were significantly shorter than cells lying opposite phloem poles. In both species, LRP originated opposite xylem poles. Our results, furthermore, strongly suggest that in regions of the root far from the apical meristem, numerous pericyclic cells undergo transverse division both previous to and during LRP initiation, decreasing in mean length throughout this period. In Daucus carota, LRP begin to form in pericyclic cells located next to the phloem poles, such cells were significantly shorter than those opposite xylem poles, even in areas of the primary root located close to the root tip. Cells also appear to divide transversely in regions far from the root tip in this species, leading to a conspicuous drop in the mean length of those cells located in portions of the pericycle destined to give rise to LRP. Two different cell populations can also be distinguished in the endodermis of Allium cepa and Pisum sativum, although observations were less conclusive in Daucus carota. In all three species, length of cortical cells was unaffected by their position opposite xylem or phloem poles.
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