Fruits
The sourness or bitterness of fruits depends on the chemical compounds present in it. These chemical compounds are acids, fructose, vitamins, starch, proteins or cellulose and dependent on the amount of each inside the fruit the content determines the specific taste portrayed by the fruits (Hulme, 1970).
Fruits which contain high levels of fructose tend to possess sweeter tastes thus making it have more sugars as part of the components. Bananas for example have a lot of starch which is later on converted to fructose as the fruit ripens. Thus the chemical processes accompanying ripening increase the amount of sugar that is present in a banana hence making it sweet (Mauseth, 2003).
The orange fruit has both the sweet and sour taste as its combination of fructose and citric acid is almost the same. Hence sometimes it can be classified as a sweet fruit and at times as a sour fruit. Lime and lemons contain elevated levels of citric acid which is responsible for the bitterness possessed by the two types of fruits (Hulme, 1970).
The reason as to why some fruits such as mangoes are sour when raw and extremely sweet upon ripening is due to the changing composition of acids and fructose. During the earlier stages of formation, fruits often contain plenty of acids which are later on converted to fructose hence a sweeter taste when ripe. Fruits with no specific taste such as melons contain equal amounts of starch and acids hence a neutral taste is obtained which cannot be overly classified (Mauseth, 2003).
The process of fruit ripening is highly responsible for the seed dispersal mechanism that will be attained by the fruit. Fruits which are dispersed by animals often undergo ripening that makes it attract and appeal to the consumers. Therefore, the enzymes responsible for ripening causes animal-dispersed seeds to have bright colors or scents which increase their chances of being noted and consumed. Similarly, fruits which are dispersed by wind or self-dispersal often undergo subsequent dehydration and drying such that by the time the fruits are almost undergoing dispersal, the seeds are light enough to get scattered further on from the parent. Another category of fruits whose dispersal is determined y the ripening procedures are the wind-dispersed seeds which are consequently dehydrated to obtain light structures (Mauseth, 2003).
Consequently, the ripening process in fruits often includes conversion of acids into starch and fructose hence making them sweet. Constantly, the elevated levels of fructose leads to a sweet fragrant scent emanating from the fruit hence increasing the degree of appeal to animal consumers. Generally, fruits are usually quite hard in the early stages of growth especially immediately after formation. However, as animal dispersed fruits are ripening, the hard skin and fleshy inner parts become softer, as well as, juicy such that animals do not require a lot of energy hence they are easily consumed (Hulme, 1970).
When human beings consume the fruits before they have dispersed the process of ripening and dispersal is interfered with. Consequently, the consumption of fruits and grains before dispersal hinders the complete formation seeds, as well as, the entire conversion of acids into starch which is used during the dominance stage. Similarly, some seeds are bound to be dispersed by wind or self-dispersal but human activities including consumption often disrupt the entire hormonal effect of the ripening process thus seed dispersal does not prevail (Hulme, 1970).
After seed dispersal, the young seeds undergo through a period of rest whereby various process such as maturation of seeds takes place. Consequently, there results a period of no activity which is associated with seed dominance and rest in preparation for germination. Similarly, upon provision of appropriate nutrients and materials which are compulsory for seed germination, the seed uses the stored starch which was never converted into fructose to provide energy associated with germination. Metabolism of stored starch inside the seed only takes place after dispersal and during germination (Hulme, 1970).
Consequently, the starch and fructose found inside the fruits is not utilized by seeds in their metabolism. The fruit and seed often have their own separate storage places for food hence there are no instances of co-sharing or dependence. Therefore, seeds do not use starch or fructose that is stored inside fruits but rater has its own store in the endosperm (Mauseth, 2003).
References
Mauseth, J. D. (2003). Botany: An Introduction to Plant Biology. Jones and Bartlett. pp. 271–272
Hulme, A.C. (1970). The Biochemistry of Fruits and their Products. Vol 1. London & New York: Academic Press
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