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67. In trees the growth rings represent : (A) Secondary phloem (B) Cork-cambium Secondary xylem o (D) Primary xylem |
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Answer» Secondary xylem Explanation: A growth layer in secondary xylem seen in a cross section of a woody STEM or branch. A layer of wood FORMED in a plant during a single period of growth. Growth rings are visible as concentric circles of varying width when a tree is cut crosswise. They represent layers of cells PRODUCED by the tissue known as vascular cambium. Most growth rings reflect a full year's growth and are CALLED as annual rings. But abrupt changes in the environment, especially in the availability of water, can cause a plant to produce more than one growth ring in a year. So, in trees the growth rings represents secondary xylem and not primary xylem, secondary phloem and cambrium. |
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