The Climacteric Rise in Fruit Respiration as Controlled by Phosphorylative Coupling.

The ripening of fruit is accompanied by a group of physiological and chemical changes whichl are characteristic and moderately uniform as between different species of plants. Typical coimiponents of the ripening process are pectic transformations which lead to fruit softening, changes in fruit color, often with the disappearance of pigment such as chlorophyll and the appearance of new secondary pigments, changes in compounds responsible for taste or odor, transformation of reserve materials such as polysaccharides to simpler sugars, and finally, changes in the magnitude of the respiratory gas exchange. The respiration of many fruits after removal from the plant follows the general course shown for the avocado in figure 1 (1). Respiration drops slowly to a low point known as the preclimacteric minimumii. At this point the fruit is still unripe. With the initiation of fruit ripening, rate of respiration rises from the preclimacteric minimum to the climacteric maximum. Edible maturity of the fruit coincides in many cases with the climacteric miiaximum in respiration, or follows this maximum by a few hours or days. Subsequent to the climacteric the respiratory rate drops steadily as the fruit passes into senescence. We have tried to get some insight into the process of fruit ripening by study of the factors which underlie the changing rate of respiration during the climacteric cycle. The sudden rise in respiration from the preclimacteric minimum to the climacteric maximunm should become understandable if one could discover the factor or factors which limit respiratory rate at the preclimacteric minimum. We have therefore studied the factors which limit respiratory rate, and in particular, the factors wlich might by alteration or increase bring about increases in rate of respiration of preclimacteric fruit.