Posted by: Sandy Steinman | May 28, 2014

Why Joshua Trees Look Different

KCET’s  The Back Forty blog answers the question: Why Joshua Trees Look The Way They Do? Here is an excerpt from the post:

Unlike trees such as oaks or pines or redwoods, the stems of Joshua trees are remarkably flexible. Other trees, hardwoods and softwoods alike, have trunks and branches that are reinforced with lignin, a polymer associated with cellulose that makes up as much as a third of the weight of the wood of many trees. Lignin makes trees rigid and that rigidity confers strength, but with such strength comes brittleness. A thick tree trunk bends only a little in a strong wind, and too strong a wind will shatter it.

Further, lignin is heavy, and so horizontal branches pose a special engineering problem for woody plants. Too much weight at the far end, and the branch will break off near its point of attachment. Lignified trees must reinforce all but the lightest horizontal branches by adding structural support, either by thickening the undersides of branches at the trunk (compression wood) or by buttressing the top of the branch to help hold it up (tension wood.)

Read the full story and learn a lot more about Joshua Trees at  Why Joshua Trees Look The Way They Do | The Hidden Desert | The Back Forty | KCET.

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