Anatomy of A Tree Primer

[DaveZ]

Thanks Tony !

[_Tony]

Late yesterday afternoon I realized that there was something that I avoided knowing for quite sometime. A post, by Dick, called it to my attention and I thought that I should finally get to it. Something as simple as the anatomy of a tree I had no clue about. That's right not a clue. As I was driving home from this prison, some call work, I felt like a complete horses ass not knowing this. So this morning I woke up riddled with guilt, broke out some of my old beginner books and surfed the web for info. The following is what I came up with. Hopefully I'll remember it all. These days my mind is set on so many different things that that'll be amazing. Now I’m far from being a botanist, but here goes:

The Anatomy of a Tree

Bark: Seem rather obvious yet the bark consists of two layers the the outer, Periderm, (kind of like the epidermis, your skin) and the Secondary Phloem, more commonly known simply as Phloem. Periderm can be several layers thick. The inner layers cut off nutrients to the outer layers resulting in dead Periderm tissue. This is also known as Cork. The Phloem prevents the bark from splitting among other things including sending important nutrients between the leaves and roots.

Cambium: consists of Early Wood and Late Wood and is a thin layer of live tissue that's immediately below the bark. It annually produces new bark and wood in response to hormones*1 that flow down through the Phloem. In early spring the Cambium produces Early Wood, the outer portion of the Cambium layer, and as the season progresses comes, obviously, Late Wood. At this point the growth season begins to slow and this portion of the layer begins to thicken and, as dormancy sets in, becomes an Annual Ring. Thus, an annual ring (or previous Cambium layer) marks one complete growing season and expands the diameter of the tree, eventually causing the old bark to crack and fall off.

Vascular Rays provide horizontal contact between the Cambium layer and the trunks interior through to the core, thePith. They appear as spokes of a wheel, so-to-speak. When wood splits, or more commonly known as Checking, it does so at the dried Vascular Rays.


Sapwood: also known as Xylem resides in the outer few centimeters of the Cambium layer. It passes water and nutrients (sap) from the roots to the leaves through many tube-like cells. It's the main artery providing the majority of the trees food. This innermost bands of this new wood, that's produced here, looses it's vitality after a few years, becoming part of the Heartwood.

Heartwood: This layer, which is the innermost bands of older sapwood, provides both strength to the tree and a place to store waste products. These waste products or Extractives are transferred inward along the Rays and stored here. These Extractives consist of resins, gums, oils and tannins and help ward off decay organisms. They eventually polymerize and form pigments that are darker, denser and give various species their attractive rich color. Since this layer is more durable than Sapwood it plays an important role in providing support. Although this layer is dead, it will not decay or lose strength while the outer layers are intact.

Pith: The inner most ring / core of the tree.

*1 These hormones are produced from food from the leaves. These hormones, known as "Auxins", stimulate growth in cells. Auxins are produced by leaf buds at the ends of branches as soon as they start growing in spring.

Something I'm not yet sure about, does an older Cambium layer become Sapwood since an older Sapwood layer becomes heartwood. As a tree grows do the layers, besides Heartwood (which is the oldest), take on a predecessors role?

Well that's what I picked up today. Now I won't feel like such a dope next time. Why did I type all this? Well typing subjects like this makes me research thus sticking it more in my memory. I also thought I'd share it with those who won't admit that they didn't know it either. Hope this helps. Boy if I did this weekly...hmmmm...

Tony

PS If there's already a primer on this, I appologise. It was more for my learning and thought someone else may benifit.

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