Botanists term fruits to be the mature seed bearing ovary of flowering plants, sometimes with other parts of the plant attached. Thus all the seed containing vegetables like eggplants and tomatoes are actually fruits. The pods of peas and beans are called legumes. They are eaten while green, but if allowed to mature on the plants, they eventually dry out and split open to release their seeds.
The fleshy fruits undergo many complex changes as they approach maturity. Color is most obvious. Tomato changes from green to red, plums become red or blue and so on. Flesh that was hard and sour, bitter or otherwise unpalatable frequently becomes soft, juicy, sweet and fragrant. All these changes are related to the fruit’s role in reproduction. The green color of immature fruit helps keep it hidden among the plant’s foliage. Unpleasant flavors also deter animals from eating it before the seeds are fully matured.
Ripe fruit, colorful and succulent, on the other hand, offers an irresistible invitation to hungry birds and other colorful creatures. When they eat the fruits, small seeds pass unharmed through their digestive tracts and later are deposited far from the parent plant, along with a dose of natural fertilizer. If the seeds are too big to swallow, animals are likely to drag the fruit off and eat it elsewhere, leaving the seeds to sprout when conditions are favorable.