Plants Run Calculations to Get Through the Night


One of the first things we learn in science class is that plants are autotrophic organisms, and they produce starch by the process of photosynthesis in the presence of sunlight and carbon dioxide. As the first sentence clearly states, plants won’t be able to generate food during night. Meaning, it has to depend on stored food reserves till dawn.

Organisms have to regulate the rate of consumption of their food reserves during the periods when it is not possible to acquire food to avoid starvation. Plants do that by making use of stored carbohydrates in the form of starch during the dark cycle. Studies conducted by a team of researchers from John Innes Centre in Norfolk on Arabidopsis thaliana has shown that concentration of starch in its leaves steadily increases during the day. The plant then consumes the starch accumulated in semi-crystalline form during the night, and its concentration drops linearly to less than 5 percent by dawn.

Observation has shown that the plant adjusts its starch consumption such that it never runs out of food before dawn. Even when the light conditions were changed to make night appear early or late, these plants were found to adapt by altering the rate of starch consumption to ensure that the reserves last till dawn.

When the duration of light exposure was shortened to reduce the quantity of reserve starch, the plants were observed to reduce their starch consumption accordingly to make it last till morning. The team attempted to trick the plants by introducing windows of light at night, but the plants remarkably adapted to the changes each time by adjusting their starch use accordingly. This has led the researchers to conclude that the plants carry out arithmetic calculations continuously during the dark cycle to efficiently manage their starch reserves, preventing themselves from starving before dawn.

The researchers have deduced that the levels of two different types of molecules represent the quantity of starch in reserve and time left till dawn respectively. The molecules representing the size of starch reserves encourages the plants to consume starch, whereas the molecules tracking time prevents the plant from using it. By dividing the former molecule by the latter enables the plant to use its reserves at a steady rate, so that it lasts till dawn. This is one of the instances where mathematical calculations are involved in a simple biological process and similar equations can be responsible for other natural phenomena as well.

It is not just plants, even the bacterial cells are found to be good at maths, and are being used to create living calculators.

Source: John Innes Centre

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