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Résumé :
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Spatial and temporal analyses of elongation and cell length of monocotyledon leaves have most often been performed during the period when leaves are visible and elongate at a constant rate (steady-state), In the present study, the focus was on the earlier stages, during the establishment of the elongation zone. Regardless of leaf development stage, the segment located between 0 and 35 mm from the leaf insertion point had a relative elongation rate that increased with distance from insertion point ('accelerating zone') while the segment located further than 35 mm had a relative elongation rate that decreased ('decelerating zone'), This stable pattern held for both young, non-emerged leaves, where it was restricted to the portion corresponding to the length of the blade, and for leaves during steady-state elongation. In the same way, the profile of cell length was essentially the same during early development and during steady-state elongation. The results of a temporal analysis of whole-leaf elongation rate, carried out in the field and in the greenhouse at different light intensities were consistent with a time-invariant pattern of elongation. Whole-leaf relative elongation rate increased with time until the leaf reached 30-40 mm length (although at different leaf ages depending on conditions), and declined afterwards. These results suggest that the patterns governing the elongation rate of a sector of a maize leaf are independent of the leaf developmental stage but depend on sector position only.
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