PROPOSED STANDARD SYSTEM OF NOMENCLATURE FOR MAIZE GRAIN FILLING EVENTS AND CONCEPTS

A system of nomenclature is proposed to standardize concepts and defin itions utilized by physiologists and breeders to refer to events of th e maize (Zen mays L.) grain filling period. Though the transition from vegetative to grain filling phase is not a discrete event, we recomme nd that agronomists utilize 80% silking as the baseline for ordinal da y counts to report events or treatments occurring during the grain fil ling phase. Of all possible baselines, 80% silking is the most objecti vely observable and directly measurable in the field, and is an accura te indicator of: the time when the majority of kernels have been sexua lly fertilized. We recommend adoption of the term gestation to refer t o the interval between tassel emergence and fruit set, a time that enc ompasses a sequence of events critical for yield determination (tassel emergence, silk emergence, pollination, syngamy, germ and endosperm d ifferentiation). The grain filling interval delimits the process of ke rnel morphosis, when kernels acquire characteristic morphological attr ibutes (size, shape, color, composition). During morphosis, kernels ca n be explicitly identified and described as: normal (progressing devel opmentally through well defined growth phases), incipient (possessing the potential to develop given sufficient time and growth factors), hy poplastic (of subnormal growth), aplastic (lacking growth) or rudiment ary (morphologically incompetent to develop). A plot of grain dry matt er accumulation per unit area as a function of time reveals four clear physiological phases undergone by kernels in normal morphosis: dilato ry, exponential, linear fill and attenuative. These phases are defined on the basis of individual ear development. The progress of ear devel opment in plant: communities must be reported statistically. This syst em of nomenclature should promote objective and precise scientific com munication regarding events and concepts related to maize grain fillin g.