Leaf morphogenesis and growth in Cyperus eragrostis (Cyperaceae)

We identified the zones of leaf extension, cell division, cell elongation, and cell differentiation in developing leaves of a sedge species, Cyperus eragrostis Lam. (Cyperaceae). The zone of leaf extension was located by measuring the separation between pinhole markers and by observing the staining pattern of Calcofluor White after pulse-labelling growing leaves. These observations were supported by determining growth rates of control and punctured leaves and by scanning electron and light microscopy of developing leaves. The location of the zone of cell division was assessed by enumerating mitotic figures, and the zone of cell elongation was established by measuring lengths of epidermal cells in cleared leaves. These studies indicated that the zone of leaf elongation is within the basal 10-15 mm of a leaf and that cell divisions are restricted to the basal 0.2-1 mm. Radial enlargement of internal tissues begins in the basal half of the elongation zone and cells are fully differentiated within a short distance above it. Expanding leaves can be divided into three zones: zone 1, a basal meristematic zone where cell division and some cell elongation occur; zone 2, a zone above the base where cells are elongating but cell division has ceased; and zone 3, a zone where elongation is complete and cells have reached their final length. This pattern of leaf development is similar to, but more condensed than, that found in the related monocotyledonous family, the Poaceae.