Biologists estimated the global scale of water transport by plants

(ORDO NEWS) — Every year, plants take up huge amounts of moisture from the roots to the tips of the leaves. It takes almost 10 trillion kilowatt-hours of energy to carry it.

Leaves, stems and other external organs of plants actively evaporate moisture. This creates a pressure gradient that causes the water to be taken up by the roots and pushed up.

This process is called transpiration and allows plants to “drink” without being able to actively move. It provides water for photosynthesis reactions, creates elastic pressure in cells, and carries nutrients.

Due to the abundance of plants, transpiration makes a significant contribution to the transport of water on a planetary scale.

Scientists from the University of California at Santa Barbara have for the first time measured this process in numbers, calculating how much energy it takes to lift such volumes of moisture.

The numbers turned out to be huge: about 9.4 quadrillion watt-hours per year, which is comparable to the productivity of all hydroelectric power plants in the world.

Biologists estimated the global scale of water transport by plants 2
The energy density required to transport water depends on the climate and the nature of the vegetation cover

For calculations, Gregory Quetin and his colleagues divided the entire land surface into sections of 0.5 degrees along the parallels and meridians.

For each plot, the calculations were carried out separately, taking into account the density and height of the vegetation cover.

As one would expect, water transfer is most intense in dense forests, especially in humid tropical forests, involving an average of 0.06 watts of energy per square meter.

This value is about a percent of the total energy that herbaceous plants receive through photosynthesis. For much taller trees, it already reaches 14-18 percent and would require quite decent expenses.

However, transpiration is a passive process that allows you to lift water, counteracting gravity without additional energy costs. Quetin and his co-authors note that without such an efficient mechanism, plant productivity would be much lower.


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