IV. AGRICULTURAL MANIPULATION OF ABSCISSION
A. Methods of Manipulating Abscission
There are a great number of crops for which the control of abscission is desirable. For example, too little
natural thinning of young fruit can result in large numbers of small unmarketable fruits, while too much
abscission results in uneconomical yields.
Techniques are slowly emerging which allow the manipulation of abscission. They can be catego-
rized as follows:
- Understanding the physiological basis of abscission. Perhaps the best way of controlling ab-
scission is to understand the physiological basis of its induction. For instance, many ornamental plants
220 SEXTONFigure 11 Dark-field micrograph of a thin longitudinal section through an abscising abscission zone of bean.
The section was hybridized to a^35 S-labeled cellulase cDNA probe. The hybridization signal is seen as bright
light reflecting silver grains in the separation layer and in the central vascular traces. (From Ref. 131.)
Figure 12 Time course of accumulation of cellulase protein and mRNA. The cellulase activity in bean ab-
scission zones kept in ethylene and air has been plotted against time. The amount of cellulase cDNA probe bind-
ing to RNA from the same preparations is also shown. The photographs are of a Western immunoblot of ab-
scission zone proteins probed with cellulase antibodies and RNA dot blots probed with^32 P-labeled cellulase
cDNA. (From Ref. 149.)