Effects of Abscisic Acid on Growth and Dormancy of Two Races of Red Maple

Northern (Massachusetts) and southern (Florida) races of red maple (Acer rubrum L) both accumulate abscisic acid (ABA) in response to short photoperiods and cold nights. Yet, only plants of the northern race develop a true winter rest. Height growth by plants of northern races is completely stopped by artificial applications of ABA. The pseudobud formed in response to ABA treatment differs markedly from the normal bud formed in response to short photoperiods and cold nights. No winter rest is induced by ABA treatment Growth and normal leaf formation are resumed by the northern race of red maple as soon as ABA application is stopped. Growth of the southern race of red maple was only slowed by the application of ABA, and no bud formation of any kind was observed. Comparison of the responses by plants of the northern and southern races of red maple to short and long photoperiods shows that concentration of ABA is correlated with, but not causally related to, the development of a winter chilling requirement and cold tolerance. Observations were made on patterns of bud growth and leaf abscission by plants of these races and of the independent behavior of stocks and scions of interracial grafts The development of cold tolerance and a winter chilling requirement appeared to be controlled by the biochemistry of the particular bud or tissue and not by substances which are formed elsewhere in the plant and transported to the bud or tissue