We all know, since our school days, trees have rings. Those rings allow us to count the age of a tree. What if someone walks up to you and says, ‘hey, did you know that the first trees on Earth didn’t have rings?’ That would be quite a shocker but again, you might end up thinking that like all those prehistoric creatures, probably those trees were also simple in structure. Unfortunately, you will be grossly mistaken! The Cladoxlopsids – the first trees on Earth didn’t have any rings and this is where the scientists are a bit puzzled.
Say Hello to Cladoxlopsids
Cladoxlopsids are a group of ancient trees from which all our modern trees and ferns have evolved. However, scientists studying fossilized tree dating all the way back to 374 million years are facing some serious challenges. A team of researchers studying the sample announced in May 2017 that the ancient tree that they are studying belonged to the Cladoxlopsids group and it doesn’t have any rings. It looks nothing like a tree from today.
The team consists of researchers from three different reputed institutes that include:
- State University of New York
- Nanjing Institute of Geology and Palaeontology, China
- Cardiff University, Wales
What did the scientists find about the Cladoxlopsids?
Did you know that trees of today have Xylem? These are specialized tissues responsible for water transportation all the way from tree roots to the tips of the tree. Interestingly, this Xylem grows in a single cylinder in most of the known trees and is located underneath the bark of the tree. As the tree grows older, the older Xylem cells die and new wood grows atop that layer of dead Xylem. The new wood called the sapwood gets its own cylindrical Xylem layer for water transportation. The older and dead Xylem layer is known as the heartwood and it is darker in color because of presence of stored oil, dye and sugar. This is how rings are created that can be seen in cross section of a tree trunk.
The scientists who studied the ancient tree found that there were no rings at all because Xylem was not grown in yearly rings. What were present instead were narrow strands located in the trunk’s outer 5 centimeters. These strands were in turn connected to each other in a web formation. So, a cross section of the sample yielded Dalmatian spots instead of rings.
Why are the scientists so confused about the Cladoxlopsids?
There’s a real good reason for the scientists to get that ‘worried face’ look. Each spot on the cross section (that is, each strand) had its very own Xylem ring. So? It actually means multiple tree trunks growing inside a single trunk! So… mini trees inside a tree! That’s weird, really weird!
According to the scientists, as the mini trees kept growing and the volume of soft tissues between the strands increased, their connections were simply split apart in a controlled fashion for accommodating the growth and then again repaired on its own so that the whole tree didn’t crumble down because of its own weight.
Also, as the diameter of the tree continued to expand year after year, the woody strands would slide down to the base of the tree from its side. This gave the characteristic bulbous shape and flat base to the Cladoxlopsids.
So, the scientists are baffled as they don’t yet understand why the ancient trees had such really complex growth mechanism.
In case you want to read the original press release, you can find it here.