I'm a highschooler and I know next to nothing about botany, but I want to learn about it.
If the secondary xylem and phloem grow, wouldn't this "squish" the internal and external parts? In the diagrams I see the plant increases in diameter and the primary parts basically "stretch" or thin out to fit the bigger circumference. Do the cells realign themselves? Cuz they move somehow right?
by Bluerasierer
1 Comment
So if we are looking at a crossection of a tree and starting with the very center (pith) the progression outwars toward bark is this: pith, primary xylem, older secondary xylem (many layers) to youngest secondary xylem, vascular cambium, youngest secondary phloem to oldest secondary phloem, cork parenchyma, cork cambium, cork cells. The three cork layers make up the periderm (outer bark)…secondary epidermis.
Older secondary xylem is to the interior of the tree with the newest layers secondary xylem closest to the vascular cambium layer. On the other side of the vascular cambium layer is the youngest secondary phloem while the oldest secondary phloem is crushed between the new layers of secondary phloem and the older layers of cork parenchyma. So as the tree is growing out the periderm is stretching, cracking and filling in while crushing the oldest secondary phloem between it and the newest secondary phloem layers.
I hope that makes sense. There is a lot happening there.