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Begins New Growth In Spring: The first group contains species and hybrids that flower in summer and fall on shoots produced during the same season. This group begins new growth in spring by developing fresh young shoots from the ends of old shoots. The second group is formed of vigorous spring- and early summer-flowering types that bear flowers on short shoots which arise from growths that have developed in the course of the previous year.
Lateral growth in trees frequently begins later than growth in height, but the period of lateral growth is longer. Rates of lateral growth likewise are low at the outset, increasing after a few weeks and then diminishing. In view of the long annual period of lateral growth in trees, deleterious environmental conditions may exercise a pronounced effect on growth. In the wood of trees of temperate regions, narrow and wide growth rings may be observed, marking years characterized by unfavorable and favorable conditions for growth.
A deficiency of growth hormone during infancy results in the development of a dwarf; these individuals are not deformed and are normal in intelligence and sexual development. An excessive production of growth hormone during infancy or childhood will lead to the development of a giant. When growth hormone begins to be produced in excessive quantities after normal growth has stopped, only the hands, feet, and chin enlarge; this condition is known as acromegaly (q. v.). |
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