THE LACK OF A RESPIRATORY RISE IN MUSKMELON FRUIT RIPENING ON THE PLANT CHALLENGES THE DEFINITION OF CLIMACTERIC BEHAVIOR

A burst in respiration coincident with fruit ripening has been used fo r over half-a-century to classify harvested fruit such as apples, bana nas, melons, and tomatoes as climacteric. In contrast, respiration slo wly declines in harvested non-climacteric fruit such as citrus and str awberries. Autocatalytic ethylene production was later recognized as a ccompanying the ripening of climacteric fruit. We developed a procedur e to insert sterile ports in netted muskmelon (Cucumis melo var. Retic ulatus Naud.) fruit to allow repetitive sampling of internal gases in both attached and detached fruit as they ripened. Detached fruit produ ced the characteristic climacteric pattern of carbon dioxide and ethyl ene production as they ripened. In contrast, fruit ripening attached t o the plant did not exhibit the climacteric increase in respiration, d espite a climacteric increase in the plant hormone ethylene. A respira tory rise was observed with fruit ripening on the plant, but only afte r they abscised. The climacteric burst in respiration, which has been widely observed with ripening, harvested fruit, may be an artifact of harvest and not a natural phenomena associated with ripening of climac teric fruit. The peak in ethylene production by ripening, climacteric fruit, whether harvested or not, might provide a more reliable criteri on for separating climacteric from non-climacteric fruit.