Discovery uncovers a new leaf for Redwoods
Redwood trees havetypes of leaves, and they do totally different
things
Date:
March 16, 2022
Source:
University of California - Davis
Summary:
Redwood trees have two types of leaves, one to make food and the
other to absorb water, found a new study. It's the first study to
estimate whole- crown water absorption in a large, mature tree. The
findings can help scientists monitor redwoods' adaptability amid
a changing climate and deepens our understanding of the resilience
of these massive trees.
FULL STORY ========================================================================== Redwoods are among the most well-studied trees on the planet, and yet
their mysteries continue to surprise and delight scientists and nature
lovers.
========================================================================== Scientists from the University of California, Davis, discovered
that redwood trees have two types of leaves, and those leaves have
completely different jobs, according to a study in the American Journal of Botany. Together, these functionally distinct leaves allow the world's
tallest trees to thrive in both wet and dry parts of their range in
California, without sacrificing water or food.
Division of labor The peripheral leaf spends its working hours
making the tree's food - - converting sunlight into sugar through photosynthesis. Its colleague, the axial leaf, does almost nothing to
help with photosynthesis. Instead its specialty is to absorb water. In
fact, the study found that a large redwood can absorb up to 14 gallons
of water in just the first hour its leaves are wet.
How does that compare to other trees? Scientists don't know. This is
the first study estimating whole-crown water absorption in a large,
mature tree. Because large redwoods have over 100 million leaves, this absorption record may prove hard to beat.
In wet forests, photosynthesis can be inhibited by films of water covering
leaf stomata when they get wet. For redwoods, the different leaf types
allow the trees to get wet and still be able to photosynthesize. The
peripheral leaves have a waxy coating that slows water absorption but
may help them continue photosynthesis throughout the wet season.
==========================================================================
"I'd be surprised if there weren't a lot of conifers doing this," said
lead author Alana Chin, a Ph.D. student in ecology with the UC Davis
Department of Plant Sciences at the time of the study. "Having leaves
that aren't for photosynthesis is in itself surprising. If you're a
tree, you don't want to have a leaf that's not photosynthesizing unless
there's a very good reason for it." Trading spaces The study also found
that leaves can shift their "office space" along the tree depending on
whether the environment is wet or dry.
In the wet, rainy north coast, the water-absorbing leaf type is found
on the tree's lower branches, leaving the upper, sunnier levels to the photosynthesizing leaf type. That dynamic flips for redwoods in their
southern range: The water-collectors live among the tree's higher levels
to take more advantage of fog and rain, which occur less often in the
drier environment.
To arrive at their findings, the authors collected shoot clusters from
six redwood trees at five forest locations stretching from wet Del Norte
County to the dry Santa Cruz Mountains and exposed them to experimental
fog. They estimated the water absorption potential for seven additional
trees - - including the tallest living tree -- and took samples at
varying heights.
==========================================================================
They then compared the anatomy and measured photosynthesis of the
peripheral and axial leaves to understand their function. They also
developed a physics- based causal model that allowed them to determine
the leaf traits that regulate absorption rates.
Amid all the findings, Chin is most excited to have found an easy
and effective way to indicate redwood trees' ability to access
fog. Researchers can monitor how and if redwoods are adapting to climate conditions and a future, drier world by simply looking at the visible
waxes covering the two types of leaves - - something that could be
captured on a cell phone camera and shared by other scientists or even
members of the public.
Superlative species Redwoods are renowned for their resilience in the
face of many natural threats and inspire numerous superlatives: They are
among the planet's biggest, tallest, oldest trees. They have tannin-rich heartwood, fire-resistant bark and pest-resistant leaves. This new
finding is another example of their ability to respond to environmental conditions, like drought and water stress.
"The cool thing here is their ability to thrive under all these
circumstances and adjust themselves to these different environments,"
said Chin, who grew up near the redwoods in Mendocino County. "That
things like this can be happening right under our nose in one of the best-studied species out there -- none of us assumed this would be the
story." Study co-authors include Paula Guzman-Delgado, Jessica Orozco,
Zane Moore and senior author Maciej Zwieniecki of the UC Davis Department
of Plant Sciences, as well as Stephen Sillett, Lucy Kerhoulas and Marty
Reed of Cal Poly Humboldt, and Russell Kramer of Dipper and Spruce LLC
in Washington.
The study was funded by the National Science Foundation and a Katherine
Esau Fellowship from UC Davis.
========================================================================== Story Source: Materials provided by
University_of_California_-_Davis. Original written by Kat Kerlin. Note:
Content may be edited for style and length.
========================================================================== Related Multimedia:
* Two_different_leaves_of_redwood_trees ========================================================================== Journal Reference:
1. Alana RO Chin, Paula Guzma'n‐Delgado, Stephen C Sillett,
Jessica
Orozco, Russell D Kramer, Lucy P Kerhoulas, Zane J Moore, Marty
Reed, Maciej A Zwieniecki. Shoot dimorphism enables Sequoia
sempervirens to separate requirements for foliar water uptake
and photosynthesis.
American Journal of Botany, 2022; DOI: 10.1002/ajb2.1841 ==========================================================================
Link to news story:
https://www.sciencedaily.com/releases/2022/03/220316132706.htm
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