Fruit Seed Dispersal and Germination Why are some fruits sweet and some sour, whereas others have no specific taste?

Most fruits offer a distinctive and characteristic taste. Fruits such as watermelon, grapes, apples, and plums are sweet in taste while lemons, grapefruits and oranges are sour. The taste of any fruit depends on the compounds present in it. Fructose, acids, vitamins, starch, proteins and cellulose can all impact taste, either singularly or when combined in different proportions with each other (Mennella & Trabulsi, 2012). Those fruits with higher levels of fructose are typically sweeter; those with more acids tend to be sourer. The rules are not always hard and fast, however. Oranges, for example, have nearly equal quantities of fructose and acids, and are therefore both sweet and sour.

The ripening process or variety of a fruit can also impact overall taste. As some fruits ripen the quantity of acid can decrease or increase (Rajjou, et.al. 2009). That explains why fruit such as raw peaches are sour or bland, but ripe ones are sweet. Similarly, the starch found in raw bananas is later converted into fructose when the fruit ripens, which makes the banana taste much sweeter. Sour fruits such as lemons and limes do not taste sweet even after they are ripe due to the presence of excessive amounts of acids. Varieties of fruit may also lead to differences in overall taste. Variations in soil quality, climate, fertilizers, and water quality may change the proportion of compounds within the fruit, resulting in varieties of the same fruit having markedly different tastes (Mennella & Trabulsi,...

Tastes naturally guide us towards our body's nutritional needs (Rajjou et al., 2012). Sweet fruits (and other foods) tend to be richer in fats, proteins, carbohydrates, and/or water. Bitter, more sour and astringent foods are typically higher in vitamins and minerals. The brain sends the body signals when it has a specific nutritional need, which can draw us towards very specific fruits and other foods.
How does the ripening of fruit affect the process of seed dispersal?

Ripening is the shift from a protective function to dispersal function in fruit and usually occurs simultaneously with seed maturation (Cain, 2000). In dry fruits, ripening consists of desiccation, or drying out, and is considered maturation. Ripening in fleshy fruits is designed to make the fruit appealing to animals that eat the fruit and pass the seeds resulting in seed dispersal. As fleshy fruits ripen, outer skins soften, fruit flesh becomes more juicy and sweet and exterior color changes. This includes fruits such as the tomato, banana, avocado, and peach. Seed pods in some fruits burst open when ripe, literally flinging seeds away or into the wind for dispersal (Wichmann, et.al, 2009).

How do humans interfere in this process by consuming grains and fruits?

When humans consume grains and fruits, seeds are often discarded during food preparation, since they are often not edible. Watermelon seeds are one such example. In cases…