DEVELOPMENTAL ANATOMY OF CYPERUS-ESCULENTUS (YELLOW NUTSEDGE)

Ontogenetic studies were made of the rhizome, tuber, and basal bulb of Cyperus esculentus (yellow nutsedge). Early in the growth of a rhizom e, cells at the periphery of the vascular cylinder divide periclinally , forming radial rows of inner cortical cells. Tubers develop at the t ips of rhizomes that originate from tubers and basal bulbs. Early in d evelopment of a tuber, a primary thickening meristem (PTM) is establis hed at the bases of young leaf primordia, which is responsible for the early establishment of the cortex. At lower levels of the developing tuber, the PTM becomes primarily a root-producing meristem that may be close to or somewhat separated from the central cylinder that consist s of individual but interconnected vascular bundles. Increases in size of the cortical and central parenchymatous regions in the tuber are p rimarily the result of the function of a ground meristem and cell enla rgement. At maturity, the parenchymatous cells are packed with starch grains. Basal bulbs originate from rhizomes that possess more complex vascular cylinders than those that give rise to tubers. The basal bulb is a greatly shortened axis with a complex set of vascular bundles th at is basically leaf traces. A PTM within the basal bulb arises near t he shoot apex. The meristem extends down in cup-shaped fashion and giv es rise to derivatives that form roots, horizontally encircling procam bial strands, and parenchymatous sectors. Procambial strands vasculari ze rhizome primordia that are initiated at the surface of the basal bu lb.