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The paper answers several questions in biology. It addresses questions like why some fruits are sweet, sour or tasteless. Detailed explanations together with examples have been put down. It also focuses on how the ripening of fruits affects the process of seed dispersal. All the seed dispersal agents have been outlined. Ways through which a human being interferes with seed dispersal process have been listed as well as how the seeds use starch found in fruits for its metabolism.
All fruits are categorized into three groups according to their taste. They are either sweat, sour or tasteless. Fruits that taste sweet contain different levels of fructose and glucose such as apples, guavas, mangoes and watermelon. Sour fruits contain different levels of acids such as ascorbic acid and citric acid. Limes and lemons are examples of sour fruits containing citric acid when raw and ripe. Taste of any fruit is determined by the compounds it contains. These compounds consist of materials like proteins, cellulose, vitamins, starch, acids, sugar, and fructose that exist in mix form in a fruit. Sweat fruits have a bigger proportion of sweat materials while sour fruits have a bigger proportion of sour materials. Hulme, A. (1970)
Ripe sweat fruits are sometimes bitter when they are raw. In such a case, as raw fruits ripen, they contain a lot of acids but the acids tend to decrease as the sugar increase until the fruit is fully ripe e.g. a mango. Fruits that are said to be tasteless, sweet and sour usually contain equals amounts of fructose and acids in it e.g. an orange. Fruits like bananas are sour when raw and sweet when ripe. A chemical change usually takes place converting the starch in the raw banana to fructose present in a ripe banana. The sour taste withers only after all the starch has been utilized. Mauseth, J. (2003). There are cases where two fruits of the same kind may appear to have different tastes e.g. two mangoes. The main cause of such difference is the existence of many varieties of the same fruit, variations in climate, soil, techniques of growth, water, manure etc. these factors changes the proportion of compounds in the fruit resulting to difference in taste. Jeannie K. (2004).
Seed dispersal occurs when a fruit containing seeds is moved away from the mother plant. There is a higher chance of a seed getting dispersed if at all the fruit is ripe. The ripening of fruits like apples, coconuts and passion fruits allows the gravity means of seed dispersal to take place. Gravity seed dispersal method occurs when the effect of gravity on heavy fruits causes them to fall from the mother plant. Fruits with hard shells may roll away to another location but water and animals are the main transmission vehicles of such fruits.
A mature dandelion and a mature maple fruit tends to develop feathery tiny parachutes and winged seeds respectively. They are light enough to provide a larger time for wind to transport them. Dispersal of seed by the wind takes place in two forms. The seeds can float on the breeze or flutter to the ground.
Plants like water lilies and palm trees produce fruits that can be dispersed by water. These fruits are mostly dispersed after they have ripened well enough to allow detachment from the mother plant. Any fruit that can be transported by water is either light enough to float on water or hollow enough to create buoyancy that can enable them float easily on water.
Squirting cucumbers and touch-me-nots are fruits whose seeds are dispersed by explosive mechanism. Self-dispersal is a physical process where a fruit explodes and discharges the seeds from the fruit. Once these fruits ripen, the seeds are ejected away from the fruit by an elastic connection.
Most animals prefer to consume ripe fruits rather than raw ones. Hence, the ripening of a fruit tends to attract animal seed dispersal method due to its bright colors or good scent. On maturing, plants like Trifolium angustifolium produce seeds covered with stiff hair. The hair attaches the seed to animal fur or human clothes so that it can be transported away from the mother plant. Plant species whose seeds are transported externally by animals have a range of adaptations for dispersal; they may have mucus, hooks, barbs or spines. Animals can also disperse fruits by ingestion. Many animals may opt to eat a ripe passion fruit rather than a raw one. Once the fruit is digested, seeds are excreted together with the human’s waste in location far away from the mother plant. Animals can also eat a fruit and discard the seed far away from the mother plant e.g. a mango. McDonald M. (2000)
Human beings can interfere with the process of seed dispersal once they consume grains and fruits. Animals, excluding humans, are the best means through which seed can be dispersed after ingestion. This is because animals can excrete their waste with seeds anywhere. With favorable conditions, such seeds can germinate and grow well. However, humans are hygienic and evolved hence their waste usually ends up in a sewage system. Some seeds are soft enough to be crashed by the teeth or during the digestion process. If such seeds contained in human waste are excreted by human beings on a land with favorable conditions for germination, they may fail to germinate because it’s obvious they could already have been destroyed.
Seeds use starch for its metabolism. Metabolism of a seed also the seed germination process uses aerobic respiration to obtain energy from the fruit provided by the plant. Sucrose is the main material used in plants and is obtained after starch has been broken down. This is a chemical change that happens once the seed has absorbed water leading to the activation enzymes. What follows is an increased respiration, duplication of plant cells and after starch has been broken down, the embryo enlarges forcing the seed coat to burst open for the growing plant to emerge. Campbell N., Reece B., and Mitchell L. (1999)