Time‐relationships in Tassel Development of Inbred and Hybrid Corn 1

EARL R. LENG KMOWLEDGE of the mode of inheritance of agronomic characters is one of the important objectives of research in plant breeding. Although study of the genetics of corn has been far more intensive and thorough than that of any other crop plant, relatively little specific information is yet available on the mode of inheritance of many of the major agronomic characters of this crop. Much of this lack of information probably results from the complex nature of such characters as rate of maturity, yield of grain, and plant size. Consideration of the separate morphological components of these characters might be expected to facilitate an understanding of their variability and inheritance. Bonnett (2, 3) and others have suggested that study of the developmental morphology of the corn plant might provide useful information on the nature and inheritance of variations in some of the more important complex agronomic characters. Rate of development in corn has received considerable attention in corn breeding programs and inheritance studies. Since it is greatly affected by heterosis, it has also been studied in attempts to determine the nature of gene action involved in this phenomenon (7). Studies of this character usually involve the period between planting and sexual maturity. It has been shown (2, 3, 4) that this period actually consists of two distinct phases in the developmental cycle of the corn plant. During the first phase, differentiation of vegetative parts occurs. This phase is terminated by elongation of the growing point, which marks the beginning of tassel differentiation (2). The second phase, commencing with tassel initiation, is the period during which the development of reproductive structures takes place, and is completed when sexual maturity is reached. The chief objectives of the study reported in this paper were to determine if inbred lines of corn showed