Super Photosynthesizer: Hyperion (The World’s Tallest Tree)

In your daily life, I’m sure you take for granted many of the photosynthetic organisms around you. However, there are some so extreme that they deserve attention, accolades, world records and sometimes a name. These ‘Super Photosynthesizers’ will be highlighted and filed under that category on the ‘Basics’ Page.

Today, for this first installment, allow me to introduce Hyperion, a coastal redwood tree in California that holds the record for the world’s tallest tree and the tallest living organism of any kind. It is 379 feet tall; refer to the figure below for a size comparison with the Statue of Liberty*.

Height comparison of Hyperion vs. Statue of Liberty
The picture of the coastal redwood is cropped and resized from an original work: The Simpson-Reed Grove of Coast redwoods (Sequoia sempervirens) by Acroterion, October 1 2009.

Hyperion does not qualify as ‘something new under the sun’ in strict existence terms because its age is estimated to be between 700 – 800 years old. However, it has only been noticed and measured by humans within the last decade. It was discovered in 2006 by naturalists Chris Atkins and Michael Taylor within a section of Redwood National Park. Its official height was confirmed by Humboldt State University professor Steve Sillett** by climbing to the top and dropping down a measuring tape. Check out the video below documenting the climb.

Coastal redwoods (Sequoia sempervirens) are generally regarded as the world’s tallest tree species, although there have been specimens of other species that rival these giants. For example, the tallest recorded tree was a Douglas fir from the Lynn Valley of British Columbia. When it was felled in the late 19^th century, it measured 414 feet. A number of coastal redwoods in old growth sections in protected areas (National Forests and State Parks) have been measured to exceed 350 feet in height. But these giants must all start as seeds. The cones of redwood trees are only about the size of an olive and can contain up to 100 seeds each. Those are humble beginnings indeed. These trees are also able to clone themselves if they are damaged or in response to other environmental conditions. Check out this video from the Redwood National and State Parks describing redwood reproduction.

Great height has other challenges as well. The various branches of these redwoods effectively exist in separate ecological niches even though they are part of the same organism. This video by the National Parks Service features a description by a ranger from Redwood National Park of the differences in needle structure between the upper and lower canopy. The needles from the upper canopy endure more extreme temperature variations and exposure to brighter sunlight, so they have a tighter shape to prevent unnecessary water loss. The needles from the lower canopy experience a more stable environment with respect to temperature, but they must compete for sunlight with the needles on the higher branches of all the surrounding trees. The needles on these branches have a more extended structure to increase their area for harvesting sunlight.

The real limitation on tree height isn’t the light requirement, but that of water. Plants transport water from their roots to the rest of the plant by a specialized tissue called xylem. This is like the plant plumbing system. Xylem tubes function as long-distance straws to pull water and some dissolved nutrients up the plant from the roots. In the case of Hyperion, that distance is more than 379 feet! This is no small feat, and trees as tall as Hyperion are pushing the limits of physics to suck water up this distance. I highly recommend the video below from the 1veritasium channel on youtube for an explanation of just how amazing this feat really is.

Here is another great breakdown of that video if you need extra info. The gist is that the microstructure of the plant cellular system allows the trees to create enormous amounts of negative pressure (-15 atmospheres) at the treetop to suck water up that high, all without allowing it to boil at such low pressures.*** Of course, I’d like to say that plants do this because of the water requirement for the light reactions, but it actually has everything to do with the dark side carbon fixation. The intake of every carbon dioxide molecule involves the release of quite a few water molecules. The uptake of carbon dioxide in the upper canopy is the driving force underlying the tension pulling the water up to the treetop. The molecular structure of the plant xylem system and the carbon dioxide uptake structures (stomata) allow for this amazing feat of physics, but at heights much beyond 400 feet they have problems. This water stress problem ultimately affects photosynthetic ability via the water pressure required for leaf expansion to capture sunlight throughout the entire organism.

The physics and fluid dynamics of water transport in a tree like Hyperion are amazing, but all trees greater than 33 feet (not particularly impressive) must perform this feat because that is the limit for pushing water up a vertical tube by atmospheric pressure. So the next time you are pondering the peacefulness of the forest, appreciate the trees’ exertion for simply pulling water up their heights. Keep it quiet, they need their concentration.

Johnna

*This is not an actual picture of Hyperion, just a cropped picture of a standard coastal redwood originally from Wikipedia. The actual location of Hyperion is quite remote, a difficult trek for even experienced backpackers. However, the exact location is also somewhat secret to protect this great specimen from overzealous fans and mischievous troublemakers.

**I dare you to e-mail him and ask him how boring it is to be a botanist. You did watch the video, right?

*** Before anyone wants to call ‘BS’ on these numbers and this phenomenon in general, let me explain a little more. It’s not exactly that the treetops are inducing such a sucking force on the water coming up from the roots. The negative ‘pressure’ is the result of cohesive tension of the liquid water being stretched up this tube. Also check out this link that further elaborates.

References:

http://en.wikipedia.org/wiki/Hyperion_%28tree%29

http://www.sfgate.com/bayarea/article/HUMBOLDT-COUNTY-World-s-tallest-tree-a-2550557.php#photo-2648829

http://en.wikipedia.org/wiki/Sequoia_sempervirens

http://www.conifers.org/cu/Sequoia.php

http://www.biologyreference.com/Ve-Z/Water-Movement-in-Plants.html

http://www.humboldt.edu/redwoods/sillett/publications/kochEtAl2004.pdf

Additional reading on redwoods and discovering the world’s tallest trees:

http://www.savetheredwoods.org/league/pdf/srl_newyorker.pdf

http://www.backpacker.com/june_2007_above_beyond/articles/12584