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Second Growth: Lateral second growth in trees frequently begins later than second growth in height, but the period of lateral second growth is longer. Rates of lateral second growth likewise are low at the outset, increasing after a few weeks and then diminishing. In view of the long annual period of lateral second growth in trees, deleterious environmental conditions may exercise a pronounced effect on second growth. In the wood of trees of temperate regions, narrow and wide second growth rings may be observed, marking years characterized by unfavorable and favorable conditions for second growth.
second growth Cycles.—Longitudinal and lateral (diametral) second growth do not proceed continuously, but rather are cyclical phenomena with periods of second growth activity alternating with periods of relative inactivity. One of the best illustrations of the periodic nature of second growth in large woody stems is to be found in the annual ring pattern which characterizes the wood of trees of temperate regions. It has been suggested recently that even in the apparently ever-growing trees of the tropical rain forest, cambial second growth is not a continuous process.
This mass of bacteria would weigh only about 1 pound. However, if the second growth of this population were to continue for another day, the mass of bacteria would weigh a trillion tons. Fortunately the second growth period is limited and is not allowed to continue this long. However, it is easy to see, given this enormously high second growth rate, why diseases like pneumonia caused by the second growth of a bacterium inside an animal host can develop and become critical in a matter of hours or days. |
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