Abstract
Ripening of ;Tydeman's Early' apples (Malus sylvestris L.) assessed by the occurrence of the respiratory climacteric was delayed by succinic acid 2,2-dimethyl hydrazide (B-9) but not by 2-chloroethyltrimethylammonium chloride (CCC), each applied 14 days after bloom. B-9 also inhibited ethylene production by fruits exhibiting the climacteric rise. Inhibition of the climacteric by B-9 was overcome by exogenous ethylene, but the latter treatment failed to completely reverse the B-9 inhibition of endogenous ethylene production.In apple fruitlets harvested within 6 weeks of bloom, ethylene stimulated respiration but did not initiate a climacteric respiratory pattern, did not induce a color change, and did not give rise to any measurable increase in endogenous ethylene production. However, all of these changes did occur in more mature fruit. These data suggest that apples have 2 physiological stages with regard to their reaction to exogenous ethylene.