DEVELOPMENT OF THE INFLORESCENCE IN WILD OATS

The morphological development of the inflorescence of wild oats and a description of the developmental course of the apex, its branches, spikelets and florets is given. Light and scanning electron micrographs illustrate the sequential stages of development of the inflorescence of wild and cultivated oats which can be divided into three periods. Vegetative development is characterized by the initiation of leaf primordia on the apex. Branch formation is initiated via double ridge-like structures on the apex. Branches of 1st, 2nd and higher order are formed and lead to branching of the panicle. Spikelet differentiation starts with the formation of the terminal spikelet on the main axis at right angles to the plane of 1st-order branches. Each branch terminates with a spikelet but the capacity for branching is unlimited. Periods of branch formation and spikelet differentiation overlap each other. Florets are differentiated in an acropetal direction within a spikelet; usually two to three fertile florets are formed, whilst an undifferentiated remainder persists at the tip of the spikelet axis. The stage of development within a panicle decreases both in a basipetal direction from the terminal spikelet and with increasing order of branching. A scale of apical development of oats is proposed, using a decimal code similar to that for the exterior development of cereals. Descriptions and definitions of the various stages in combination with photographs of some important stages are provided. © 1990 Annals of Botany Company.