When you take your finger nail and scrap the outer bark of young tree stems you may see green. The green is CORTEX which contains chlorophyll. Chlorophyll is constantly produced.
A cortex envelops entire trunks of maturing tree trucks too. Some species shed the outer phellem leaving much active chlorophyll containing cortex year round near the surface.
Most woody roots have a cortex and no chlorophyll. Not efficient to have there.
Cortex are one of the unique features of trees above and below ground.
Here is a 3.5' DBH sycamore tree.
Trunk cortex is green in young trees and can photosynthesize when conditions are proper, even when leaves are gone. One reason we suggest not to wrap young tree trunks and block this feature on young struggling trees.
Species with big corky bark. such as oaks, will at times have green cortex near the surface in the fissures. Click here for pictures.
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