Experiments on Growth in Length of Plant Organs

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Abstract
It is shown that the growth in length of various coleoptiles, epicotyls, and hypocotyls is enhanced at oxygen tensions below that of air, though reduced when the oxygen percentage is 3.5 or less. Root extension is depressed at all oxygen percentages below 21. This effect is observed within 15 minutes. An hypothesis to account for the differential effect at 20° C. of reduced oxygen concentration on growths of roots and shoots is outlined, and preliminary experiments to test the hypothesis are described. Oxygen concentration had similar effects on the fresh weights of roots, coleoptiles, and epicotyls as on the lengths of these organs. The development of lateral roots and root-hairs was retarded by reduction of the oxygen concentration to 8.5 and 3.5 per cent. In 1.5 per cent. oxygen the retardation was very marked and injury often apparent. Complete suppression of laterals and root-hairs occurred in 0.5 per cent. oxygen.