Bananas and apples continue to ripen after being picked. Cherries and grapes do not. The difference between climacteric (后熟的) and non-climacteric fruits matters to fruit growers and greengrocers, who must ensures their products are in excellent condition when arriving at the marketplace. But how those differences originally came about remains unclear.
In a paper in Biology Letters, Fukano Yuya and Tachiki Yuuya of the University of Tokyo offer a suggestion. Fruits, they observe, exist to solve a problem faced by all plants - how best to spread their progeny around. Wrapping their seeds in a sugary flesh, to provide a tasty meal, serves as a way to got animals to do this for them. They do, however, need to ensure their fruits favour the animals most likely to do the distributing. They propose that climacterism or non-climacterism is a way to achieve this. If ground-living animals are the main distributors, then the continuing ripening of fallen fruit is beneficial. If, by contrast, those distributors are tree-living or flying animals, which can feed on unfallen fruit, then non-climacteric fruits will do well.
To test their idea, the two researchers combed through 276 papers about 80 sorts of fruits. They discovered 35 of these fruits were eaten by both groups of animals. But of those where one group or the other were the dominant consumers, 15 of the 19 eaten mainly by ground-living animals were climacteric.
Their assumption is strengthened by other evidence. They point out non-climacteric fruits tend to have vivid colors which may help them stand out amid the leaves, advertising their presence. Climacteric fruits are generally better hidden, making them harder to spot until they have fallen to the ground.