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Root and Root Hair Growth in Relation to Supply and Internal Mobility of Calcium

Oat (Avena sativa L.) seedlings were grown in (a) complete nutrient solutions, (b) calcium-deficient solutions, and (c) moist air. Calcium content of roots before and after treatment was determined by atomic absorption. Confirmatory experiments were performed with 45Ca to ascertain the mobility of calcium from seeds to roots and from one root to another in the same seedling. The calcium content of roots in moist air and in calcium-deficient solutions was considerably less than in complete nutrient solutions, while root hair elongation was greatest in moist air. Relatively small amounts of calcium may be sufficient for root hair growth if roots are not in toxic ionic environments. Deformation and suppressed elongation of root hairs in calcium-deficient solutions appear to be due to the toxicity of other ions rather than to the lack of calcium, since there was no loss of calcium from roots in this medium. Experiments with 45Ca showed that calcium in seeds is transported to roots and is used in hair elongation. However, in a divided-root-system experiment, 45Ca absorbed by one root was not transported to another in the same seedling.