INTERPRETATION OF THE MORPHOLOGY OF VARIOUS NATURALLY OCCURRING ABNORMALITIES OF THE INFLORESCENCE OF WHEAT (TRITICUM)

Abstract

At the onset of inflorescence production, the shoot apex continues to initiate leaf primordia, in the same alternating sequence of the foliage primordia below. Buds arise so precociously in the axils of the primordia that the apex appears to be producing double structures, the so-called "double ridges". The buds rapidly develop into lateral spikelets but the subtending leaf primordia remain rudimentary. After producing some 20–25 such primordia, the apex initiates the glumes and lemmas of the terminal spikelet, still continuing the same distichous sequence. Occasional deviations from the normal pattern of development seem to be the cause of some of the abnormal inflorescences which may be found: for example, the leaf primordium subtending the lowest lateral spikelet may grow out into a small foliage leaf, or the buds may grow out into side heads instead of single spikelets, or the spikelets may become abnormally elongated. Other abnormalities, such as "banana" twin spikelets and Y-forked heads are less easily "explained". The morphology of still unreported abnormalities can probably be predicted. The relative rarity of freak heads spotlights the stability of growth correlation which is achieved during the morphogenesis of normal inflorescences.