Some fruits are sweet and some sour while others have no specific taste. Fruits have different characteristic tastes depending on the nature and proportion of organic compounds (producing flavor and odor) present in them. Virtually all fruits contain cellulose, protein, starch, vitamins, organics acids and fructose in varying concentrations and proportions in different fruits (Clarke, 2009). Sweet fruits have higher concentrations of fructose (natural sugar) while sour ones contain more or excessive acid. The acid-fructose balance in fruits determines their taste. Acid content produces bitter or sour taste while fructose produces sugary and sweet taste. If the amount of fructose is equivalent to that of acid in a fruit, such a fruit will have no specific taste. Immature fruits are generally very sour/bitter due to high acidic content. As the fruits mature towards ripening, the concentration of acids decreases while fructose inversely increases except in few fruits like lemon.
Ripening of fruit directly affect the process of seed dispersal to a greater extent. Immature raw fruits contain the highest levels of acid. At this early stage of development, the fruits are very bitter and the seed are still underdeveloped and grossly immature therefore they cannot be eaten by animal agents of seed dispersal. This explains why the immature seed of the war fruits could not be dispersed. When the fruit ripens, however, the amount of acid content is gradually reduced and the amount of fructose (monosaccharide carbohydrate) increases hence the sweet taste. Fully ripe fruits are sweet with an attractive smell and an appealing bright physical look due to the presence of excess fructose and other organic ester compounds (Clarke, 2009). These features attract human and other animals to eat fleshy succulent parts of the fruits that contain mature seed in readiness for dispersal. This is the mechanism for seed dispersal.
Humans do interfere with the process of ripening in a number of ways. Considering that humans relies on fruits and grains for food, premature consumption of tender green fruits and grains disrupts the full development of the underlying seeds within the fruit. It is most notable that when immature fruits whose seeds have not grown to maturity are eaten, the seeds cannot germinate upon dispersal because the underlying embryo is not yet fully formed at the time of dispatch. Consequently, the success of seed dispersal is greatly affected by human consumption of raw grain and fruits. Secondly, consumption of grains and fruits disrupts the process of ripening. Before complete ripening, the pods and testa are still thick and they could not be split easily to release the seed after dispersal. In general, the humans interfere greatly with the seed dispersal by reducing the success rates of germination and embryo development.
The seed use fructose and starch in the fruits for its metabolism. The living embryo relies on fructose or starch as the only source of energy that it requires for growth and development. During various physiological processes such as respiration within the embryo, the biochemical molecules of fructose and starch stored in seed cotyledons are the primary substrate upon which enzymes act to release energy in the form of Adenosine Diphosphate (ADP) and Adenosine Triphosphate (ATP). Additionally, the constituent monosaccharides molecules derived from fructose and starch are the building blocks that form the living matter of the protoplasm within the developing embryo (Zimmermann, 2008). There is a constant conversion of monosaccharides (constituents of fructose) into its storable form (starch) within the seed for future use during seed germination of the seed. In summary, the seed relies on the starch and fructose of the fruit for the development of its embryo.