No abstract

PREVIOUS STUDIES of the meristem in the Gramineae have given little attention to varietal differences and the influence of temperature in early development of the shoot. This study was undertaken to determine what ontogenetic differences are present in the early development of four varieties of Avena sativa and what effect temperature may have on the development of each variety. Four varieties including a brachitic dwarf were grown at 16°C. and 28°C. The size, structure, and form of the mature oat plant is controlled by the pattern of differentiation from the meristem during formative stages. Therefore a study of the meristem should be of value in understanding the morphology of the mature plant. All the leaves are initiated during the first 3 weeks in the four varieties growing at both high and low temperatures. At the high temperature, foliage development is somewhat more rapid and cell division, resulting in initiation of each new leaf primordia, is observed 2 or 3 days earlier than at the low temperature. The 3-week period of leaf initiation is considered the vegetative or formative period. Panicle differentiation follows rapidly after the initiation of all leaf primordia. At 28°C. panicle formation is inhibited. Thus environmental factors in the early stages have a determining effect on the mature plant. Varietal differences which are prominent in the mature stages are also apparent in the structural development of the shoot.