How tall can a tree grow? – Valentin Hammoudi

Reaching heights of over 100 meters, Californian sequoias tower over Earth’s
other estimated 60,000 tree species. Growing in the misty Sierra Nevada
mountains, their massive trunks support the
tallest known trees in the world. But even these behemoths seem
to have their limits. No sequoia on record has been able
to grow taller than 130 meters – and many researchers say these
trees won’t beat that cap even if they live for thousands of
years to come. So what exactly is stopping these trees
from growing taller, forever? It all comes down to sap. In order for trees to grow, they need to bring sugars obtained
from photosynthesis and nutrients brought in through the root
system to wherever growth is happening. And just like blood circulates in
the human body, trees are designed to circulate two kinds
of sap throughout their bodies – carrying all the substances a
tree’s cells need to live. The first is phloem sap. Containing the sugars generated in
leaves during photosynthesis, phloem sap is thick, like honey, and flows down the plant’s phloem tissue
to distribute sugar throughout the tree. By the end of its journey, the phloem sap has thinned
into a watery substance, pooling at the base of the tree. Right beside the phloem is the tree’s
other tissue type: the xylem. This tissue is packed with nutrients and
ions like calcium, potassium, and iron, which the tree has absorbed
through its roots. Here at the tree’s base, there are more of these particles in
one tissue than the other, so the water from the phloem sap is
absorbed into the xylem to correct the balance. This process, called osmotic movement, creates nutrient-rich xylem sap, which will then travel up the trunk to
spread those nutrients through the tree. But this journey faces a formidable
obstacle: gravity. To accomplish this herculean task,
the xylem relies on three forces: transpiration, capillary action,
and root pressure. As part of photosynthesis, leaves open
and close pores called stomata. These openings allow oxygen and carbon
dioxide in and out of the leaf, but they also create an opening through
which water evaporates. This evaporation, called transpiration, creates negative pressure in the xylem,
pulling watery xylem sap up the tree. This pull is aided by a fundamental
property of water called capillary action. In narrow tubes, the attraction between water molecules and the adhesive forces between the water
and its environment can beat out gravity. This capillary motion is in full effect
in xylem filaments thinner than human hair. And where these two forces pull the sap, the osmotic movement at the tree’s
base creates root pressure, pushing fresh xylem sap up the trunk. Together these forces launch sap
to dizzying heights, distributing nutrients, and growing new
leaves to photosynthesize – far above the tree’s roots. But despite these sophisticated systems, every centimeter is a fight
against gravity. As trees grow taller and taller, the supply of these vital fluids
begins to dwindle. At a certain height, trees can no longer afford the lost water
that evaporates during photosynthesis. And without the photosynthesis needed
to support additional growth, the tree instead turns its resources
towards existing branches. This model, known as the “hydraulic
limitation hypothesis,” is currently our best explanation for why
trees have limited heights, even in perfect growing conditions. And using this model alongside
growth rates and known needs for nutrients
and photosynthesis, researchers have been able to propose
height limits for specific species. So far these limits have held up – even the world’s tallest tree still falls
about fifteen meters below the cap. Researchers are still investigating the
possible explanations for this limit, and there may not be one universal
reason why trees stop growing. But until we learn more, the height of trees is yet another
way that gravity, literally, shapes life on Earth.

100 thoughts on “How tall can a tree grow? – Valentin Hammoudi

  1. TED-Ed the tallest trees on earth are Sequoia Sempwevirens or the Redwood not Sequoiadendron giganteum, the giant Sequoia, Redwoods grow in the coastal ranges of Norther California and Southern Oregon, Sequoias grow in the Sierras

  2. If we could terraform Mars, and if we could build biosphere there.
    We will be able to see a deep forest with 300m tall trees

  3. Most of the tallest tree facts in the video are about Coast redwoods, not the tree commonly referred to as Sequoias. The common name Sequoia refers to the Giant Sequoia, which grows in the Sierra. Coast redwoods are the tallest known trees, and they grow in the coast ranges of California.

  4. How to make tree taller: GIVE IT A HEAAAAARRRTTTT (Californian Teen Develops New Field of Herbaceous Cardiology)

  5. If you cut it down, you will never know.



  6. They didn't mention how this area has a nearly constant mist, helping with tree's water needs despite besides what it gets from its roots.

  7. If this is how i learn about floem and xylem back in middle/high school, damn right i would ace my exam!

  8. As a California native, I can tell you the tallest of the redwoods are not in the Sierra Nevada at all, but along the northern coast of California. They are Sequoia Sempervirens. The Sierra Sequoias are another sub-species.

  9. If gravity is ultimately the main limit on growth, would trees then continue growing indefinitely in low- or zero-gravity environments?

  10. I really want to know the answer to this. How many people (i.e. animators, script writers, researchers, etc) does it take you to produce one video usually? Because the information is phenomenal and very beautifully made!

  11. Phloem, xylem.. I did study in high school. Thanks for this video and ofcourse the awesome animation Ted-Ed

  12. 0:54 Then the tress can grow their trunks, can't they????
    Phloem just always comes down, so it doesn't matter.
    And you guys say xylem sap needs to be transported only to the places with growth.

  13. Anyone reminds me of the movements of the animations are like from the amazing world of gumball? Yeah , but in a scientific nutshell about trees.

  14. Seems a bit useless and unnecessary of a question, but couldn't you just stick a pump in the tree to help get the xylem up higher? Sure you'd get the tree growing higher, but it does seem rather unnecessary.

  15. Actually capillary action is only effective up to a few centimeters. It's actually hydrogen bonding that allows plants to pull water up from their roots to the tops of trees.

  16. Best YouTube channel in the world …. But I hope that all the video goes back to the Arabic language

  17. If we eliminated gravity would it mean a tree could grow much higher? Or would the lack of gravity cause even more problems with providing nutrition?

  18. Does this mean there’s also a limit to human height? Or no because the muscle that pumps the blood can grow?

  19. If trees only knew how much CO2 humans have added to the upper atmosphere…they don’t know what they’re missing

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