Plants are true power lifters when it comes to lifting water.
For a tall tree, drinking hundreds of liters of water a day to its leaves or needles, where photosynthesis takes place, can be a lot of money. Even with short grasses and shrubs, rising sap must somehow overcome the resistance of gravity and plant tissue. Now, a first-of-its-kind study has estimated the amount of energy needed to lift sap to the leaves of plants around the world — a staggering amount that’s nearly as much as all the hydroelectric power produced globally.
In a year’s time, Plants harness 9.4 terawatt-hours of sap pumping capacityClimatologist Gregory Quetin and colleagues reported on August 17 at Journal of Geophysical Research: Biogeoscience. This is about 90% of global hydropower generation in 2019.
evaporation of water from leaves Pushing the suction pulls the sap upward, says Quetin of the University of California, Santa Barbara.Serial Number: 3/24/22). To estimate total annual evaporation from all plants on Earth, the team divided a map of the world’s land area into cells spanning 0.5° of latitude and 0.5° of longitude and analyzed data on the mix of plants in each cell. Actively pump sap every month. Unsurprisingly, the power required is highest in wooded areas, especially in tropical rainforests.
The researchers found that if plants in forest ecosystems had to use their own energy stores to pump sap, rather than relying on evaporation, they would need to consume about 14 percent of the energy produced through photosynthesis. Grasses and other plants in non-forest ecosystems need to consume more than 1% of their energy stores, mainly because these plants are shorter and less resistant to sap flow within tissues than woody plants.