Oldest Trees Appear To Be The Most
Complex That Ever Existed (text in english)
The fossilized remains of a tree
that lived 374 million years ago suggest that the earliest trees we know of
might also have been the ones with the most complex internal structure in the
history of our planet.
The study, published in the
Proceedings of the National Academy of Sciences, focused on the fossils of
cladoxylopsids. While trees today have a central vascular system called a xylem
at their center, these ancient specimens had multiple xylems located in the
outer 5 centimeters (2 inches) of the trunk.
The international team of
researchers say this distribution suggests that those trees grew in a different
way than their modern counterparts. Nowadays, trees grow rings around their
central xylem, with each ring usually representing a year of its life. In the
ancient cladoxylopsids, rings grew around every single xylem. The scientists
point out that this looks like they are multiple trees inside a single one.
“There is no other tree that I know
of in the history of the Earth that has ever done anything as complicated as
this," co-author Dr Chris Berry from Cardiff University said in a
statement. "The tree simultaneously ripped its skeleton apart and
collapsed under its own weight while staying alive and growing upwards and
outwards to become the dominant plant of its day.
“By studying these extremely rare
fossils, we've gained an unprecedented insight into the anatomy of our earliest
trees and the complex growth mechanisms that they employed.
"This raises a provoking
question: why are the very oldest trees the most complicated?”
Dr Berry has worked on many
different fossilized trees and forests, but has maintained a particular focus
on cladoxylopsids for nearly 30 years. For a long time, the fossils were but
fragments, until a well-preserved cladoxylopsids tree trunk was uncovered in
north-west China.
“Previous examples of these trees
have filled with sand when fossilized, offering only tantalizing clues about
their anatomy," Dr Berry added. "The fossilized trunk obtained from
Xinjiang was huge and perfectly preserved in glassy silica as a result of
volcanic sediments, allowing us to observe every single cell of the
plant."
While the researchers focus on trees
and their growth, there is also another interesting angle. Berry hopes to
understand how much carbon dioxide these trees were capable of storing and how
this impacted the climate.
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