Plants use less water than previously assumed

Plants use less water than earlier studies had indicated and freshwater passes more rapidly through soil than previously thought, new research using NASA satellite shows.

More than a quarter of the rain and snow that falls on continents runs off directly, ending up in the ocean, new findings showed.

Of the water that does not run off, two-thirds is eventually released by plants during photosynthesis.

The last third evaporates -- mostly from plant leaves, with a few percent evaporating from bare ground or water.

"Some previous estimates suggested that more water was used by plants than we find here," said first author Stephen Good from University of Utah.

Good said that means "either plants are less productive globally than we thought, or plants are more efficient at using water than we assumed".

The study also found that water released by plants during photosynthesis versus water evaporated from a water body, such as a lake, contains different ratios of hydrogen and the hydrogen isotope deuterium.

Researchers from the University of Utah, Salt Lake City and Oregon State University, Corvallis, analysed the two forms of hydrogen in atmospheric water vapour as measured from space by the Tropospheric Emission Spectrometer (TES) on NASA's Aura satellite, and also in global water samples.

Understanding how precipitation, plants, soil, groundwater and other fresh water interact is important for improving large-scale climate models and regional and local hydrology models, researchers noted.

The findings were published in the journal, Science.