A PROPOSAL FOR A DECIMAL SCALE OF THE INFLORESCENCE DEVELOPMENT OF WHEAT

The development of the inflorescence of wheat is outlined and accordin g to the morphological changes on the shoot apex a scale with decimal code (DC) has been proposed in analogy with the decimal code used by Z a d o k s et al. (1974) to classify growth stages of cereals. Microgr aphs from the scanning electron microscope are presented to illustrate the individual developmental stages until the formation of the termin al spikelet. The proposed scale distinguishes 10 basic developmental s tages as follows: germination (0), vegetative development of the shoot apex (1), spikelet formation and differentiation (2), floret formatio n and differentiation (3), growth of florets (4), inflorescence emerge nce (5), anthesis (6), milk development (7), dough development (8), ri pening (9). To achieve a more detailed description each stage is furth er divided into 10 substages. Hence, the whole plant development compr ises DC 00 to DC 99. The apex development during the period when the f irst leaf comes out of the coleoptile until the end of the ear develop ment within the sheath of the uppermost leaf corresponds to stages DC 1 to DC 4. The stages DC 0 and DC 5 through DC 9 of the scale are as d efined by Z a d o k s et al. (1974). The codes used for the descriptio n of the apex development are not identical with the same code for the exterior morphology of the Zadoks scale. In other words, the apical d evelopmental code of a plant need not be identical with the code of th e external growth stage of Zadoks and vice versa. The proposed decimal code scale enables an accurate and detailed description as well as an evaluation of changes occurring on the developing inflorescence. Furt hermore, systematic description as well as computer processing of data on apical development are made possible.