APICAL DOMINANCE IN MALUS
DOMESTICA BORKH: THE POSSIBLE ROLE OF INDOLE-3-ACETIC ACID
WANG, SHIOW Y
FAUST, MIKLOS
LINE, MICHAEL J
- United States Department of Agriculture
Agriculture Research Service, Fruit Laboratory
- Rm. 120, Bldg. 004, BARC-, Beltsville MD 20705
FAX: 301-504-5062
ARS Report Number: 0000033453
Summary:
Temperate-zone fruit trees, including apple, occasionally become dormant to survive
certain stresses. In general, there are two types of dormancy occurring during the summer
and winter, respectively. Plants can be reactivated easily to grow during summer dormancy
by removing the terminal bud from the shoots. In contrast, winter dormant plants must be
exposed to low temperature for a given length of time to be able to resume growth, but
require less cold if the terminal bud is removed. Thus the terminal bud plays an important
role in dormancy. We have recently discovered that during dormancy the water of the cells
is bound to macromolecules and is freed prior to resumption of growth. We examined the
role of terminal buds in maintaining boundness of water and possibly changing membrane
permeability of the bud to allow new water to move in. We report that intact terminal buds
maintain boundness of water. Boundness was also maintained when the terminal bud was
replaced by an artificial form of a hormone known to be produced by the terminal bud. We
have also discovered that changes in the water status occurs within 2 days, whereas
membrane changes occur after 4 days, indicating that the terminal bud, through its
hormonal influence, maintains dormancy generally termed "apical dominance".
These data indicate that hormone produced in top buds play a major role in the dormancy of
lateral buds. This study is significant in understanding the mechanism of dormancy and
will stimulate further research by others concerned with the mechanism of dormancy in
perennial crops.
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