Biology 101 / Photosynthesis

Photosynthesis

If we were to draw some observations between plants and automobiles we can make the following analogies . Sunlight would be the plant 's gasoline as it is the source of energy for the plant . The leaves would be the engine of the plant as it converts the plant 's fuel (sunlight ) into a form usable by the plant (ATP and glucose ) similar to how automobile engines convert fuel into mechanical energy . Similar then to how automobile makers seek to design and create the most efficient and powerful engines , plants have also

evolved ways to make their leaf engines very efficient in their task of converting solar to chemical energy

One way that plants have evolved into having very efficient engines is by having very broad leaves . Broader leaves have a larger surface area by which to catch sunlight . By catching more sunlight , the leaves are able to produce more nutrients via photosynthesis . If we have two similar plants which differ only in the size of the leaves , the plant with the larger leaves will be able to create more nutrients for any given amount of time and sunlight exposure . Therefore in an event of a crisis , the broad leafed plant will have the advantage over the other plant . In the mantra of survival of the fittest , having larger leaves means more efficient energy generation and thus plants with broad leaves will be more successful evolutionary

Heliotrophism is another mechanism by which plants are able to be more efficient in their energy transformation . Heliotrophism means that plants will tend to orient themselves in the direction of the sun . This means that the catching potential ' of the leaves is utilized to the maximum extent by virtue of always facing in the direction of most sunlight

Sleep movements is another way by which leaves become more efficient While broad leaves and heliotrophism improve sunlight intake , sleep movements reduce energy loss . By drooping down during the night , plants are effectively able to minimize the surface area of the leaves - the opposite effect of having broad leaves in the first place . However during the night no sunlight is available and the broad surface areas of leaves will lead to lost energy through nocturnal chilling . By folding down the leaves , the rate of energy loss incurred in the leaf is reduced during the night

In plant canopies , leaf orientation plays a major part in improving the efficiency of photosynthesis . Due to the crowded environment at the tops of trees , plants have evolved ways of maximizing the available sunlight In the upper layers of the canopy , the leaves are more vertically oriented compared to leaves in the lower layers which are more horizontal . The lower leaves are more horizontal since they will be catching the few bits sunlight that passes through the upper layers . In the upper layers where there is no obstruction , the vertical inclination allows the leaves to maximize sunrise and sunset light which arrives at an acute angle to the ground

Bibliography

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