Morphology and Photoperiodic Responses of Yellow Nutsedge

Abstract

Young vegetative clones of yellow nutsedge (Cyperus esculentusL.) were propagated by subdivision of older clones and then grown 6 months under photoperiods of 8 to 24 hr. Early stages of development of basal bulbs, tubers, and flowering structures were characterized in terms of apical meristem activity and differentiation of various foliar appendages: cladophylls, prophylls, leaf primordia, foliar tube development, and involucral leaves. Ramification of the axial stem system was interpreted as a repeating phylogenetic sequence:viz., undifferentiated axial meristem (from basal bulb) å primitive stem (rhizome) å advanced stem (new basal bulb). New photosynthetic leaves differentiated every 4.5 to 5 days, and each exhibited a sigmoid pattern of growth for 24 to 40 days. As photoperiods increased from 14 to 24 hr, certain active vegetative processes—total peripheral shoot development, rhizome proliferation, and rate of higher order shooting—were progressively promoted. The rate of differentiation of indeterminate rhizome tips into basal bulbs (new shoots) was maximum at 16 hr and into tubers at 8 to 12 hr. Delayed tuberization, however, occurred even at the longest photoperiod. Flowering occurred only at photoperiods of 12 and 14 hr. Active vegetative processes were competitive with tuberization, and flowering was competitive with both active and dormant vegetative development.