IN VITRO TESTS OF ABSCISSION AGENTS

Abstract

The physiology of abscission in the excised laminar abscission zone of the Valencia orange (Citrus sinensis var. Valencia) was studied. Expts. on excised tissues were conducted to determine the effect on abscission of: various fractions of blade tissue, immersion in dist. water, sucrose, chloral hydrate, indoleacetic acid, 2,4-D, ethylene and cyanamid. All treatments except ethylene inhibited abscission. Many treatments brought about enlargement of the tissues proximal to the abscission zone. It is suggested this may have been the result of interference with free movement of materials by the suberized cells which form a layer surrounding the vascular tissues in the inner cortex and another distal to the abscission zone in the cortical tissues. This investigation indicates the value of the use of excised tissues for studying abscission in the laboratory by a method which is convenient and which gives results comparable (with explainable exceptions) to those obtained under field conditions,.