Growth and Respiratory Response of Fig (Ficus carica L. cv. Mission) Fruits to Ethylene

Growth in diameter of the fig (Ficus carica L. cv. Mission) fruit takes place in three distinct periods; two periods (I and III) of rapid growth are separated by a period (II) of slow growth. With respect to exposure to ethylene, the fruit exhibits a two phase response. Ethylene inhibits fruit growth in phase A (period I), the period of cell division, stimulates growth in early phase B (early period II), and stimulates both growth and ripening during the remainder of phase B (late period II and period III). The adverse effect of exogenous ethylene on fruits during phase A is thought to be due to inhibition of cell division. The gradual transition occurring in the response of fruits during phase B was interpreted in terms of carbohydrate level in the fruits.The onset of period III and a respiratory climacteric rise was preceded by or concomitant with a sudden burst of endogenous ethylene synthesis. This, together with the fact that exogenous ethylene applied at the proper stage of fruit growth triggers both ripening and the climacteric rise, leads to the conclusion that ethylene is the causal agent. In other words, the data support the concept that ethylene is a growth hormone that initiates a chain of metabolic and physiological events leading to fig fruit ripening.