Climacteric (botany)

The climacteric stage of fruit ripening is associated with increased ethylene production and a rise in cellular respiration and is the final physiological process that marks the end of fruit maturation and the beginning of fruit senescence. Its defining point is a sudden rise in respiration of the fruit, and normally takes place without any external influences. After the climacteric period, respiration rates (noted by carbon dioxide production) return to or dip below the pre-climacteric rates. The climacteric event also leads to other changes in the fruit, including pigment changes and sugar release. For those fruits raised as food, the climacteric event marks the peak of edible ripeness, with fruits having the best taste and texture for consumption. After the event, fruits are more susceptible to fungal invasion and begin to degrade by cell death. If a fruit were to over-ripen, it could be detrimental to the post harvest of the fruit, meaning the shipment and storage of the fruits for marketing. Recent research on ethylene production and perception systems seems to show that this simple classification (fruit ripening that needs ethylene means climacteric vs. fruit ripening that does not need ethylene means non-climacteric) is not completely satisfactory: for example, there are non-climacteric varieties of melon (although almost all of them are climacteric), and grapes (classified as non-climacteric) have many ethylene-sensitive receptors, the expression of which is modulated during ripening. == Ethylene production ==

Ethylene is a hormone in plants known for its role in accelerating the ripening of fleshy fruits. In other words, a small amount of ethylene in mature, climacteric fruits, will cause a burst of ethylene production and induce even ripening. The generation and progression of this temporal ethylene signal is controlled by a range of epigenetic mechanisms. Ethylene production begins with the S-adenosylation of methionine (Met) to S-Adenosyl methionine (SAM) by SAM synthetase. SAM is then converted into 1-aminocyclopropane-1-carboxylic acid (ACC) and 5ʹ-methylthioadenosine by ACC synthase. 5ʹ-methylthioadenosine is then recycled back into Met, and the ACC is oxidised to ethylene by ACC oxidase. Ripening includes many changes in fleshy fruit including changes in color, texture, and firmness. Additionally, there may be an increase in certain volatiles (metabolites the plant releases into the air) as well as changes in sugar (starch, sucrose, glucose, fructose, etc.) and acid (malic, citric, and ascorbic) balance. These changes, particularly in sugars, are important in determining fruit quality and sweetness. == List of climacteric and non-climacteric fruits ==

Climacteric fruits • Apples • Apricots • Avocados • Bananas • Cantaloupes • Cherimoyas • Durians • Guavas • Kiwifruits • Mangos • Papayas • Passion fruits • Pawpaws • Peaches (including nectarines) • Pears • Persimmons • Plums • Tomatoes Non-climacteric fruits • Blackberries • Blueberries • Cherries • Citrus fruits • Cranberries • Cucumber • Dates • Eggplant • Grapes • Lychee • Okra • Peas • Peppers • Pineapples • Pomegranates • Raspberries • Strawberries • Summer squash • Syzygium (Rose apples, Brush cherries etc.) • Tamarillos • Watermelon ==References==