Developmental studies on the panicle initiation in sorghum

Moench) panicle was made from photographs of fresh apices and from stained sections of fixed material. From periodic collections, the transition from vegetative to reproductive stages indicated an acropetal initiation of primary branch primordia. Higher orders of branch primordia are commonly found on lower branch primordia. Differentiation of spikelets in the panicle is basipetal and is marked by the appearance of glume primordia. Both fertile and sterile spikelets of a pair are morphologically similar during their early development, but the floret parts of the latter degenerate as the inflorescence matures. A developmental stage system evaluating the degree of panicle development is proposed. Three factors considered to be of importance in the control of yield, which are associated with the development of the inflorescence, are number of primary branch primordia, number of branches arising from each primary branch, and the timing of spikelet differentiation.. Of these, the time sequence of acropetal differentiation of primary branch primordia followed by basipetal differentiation of spikelets may be the most important in controlling yield.