, Volume 29, Issue 3, pp 317-335

Natural variation in nuclear characters of meristems in Vicia faba

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The natural variation in chromosome size in root-tip and shoot apex meristems of Vicia faba has been studied. Chromosomes in main root-tips of one week old plants are 2–3 times larger than those in small lateral root-tips of 3 week old plants. While the nuclear DNA content remains constant, the nuclear RNA and nuclear histone contents show a positive linear correlation with chromosome volume. The DNA: histone ratio varies and is lowest in cells with large chromosomes. Nuclear volume and chromosome volume are not linearly related and changes in nuclear density therefore seem likely. A positive linear relationship between chromosome volume and mitotic index in colchicined squashes is demonstrated. The results strongly suggest that variation in chromosome size indicates a corresponding change in the rate of cell metabolism and may well reflect change in genetic activity.