On the effect of carbon dioxide on geotropic curvature of the roots of Pisum sativum L

Many physiologists have shown that, in general, carbon dioxide exercises a narcotic or toxic influence on vegetable protoplasm, temporarily or permanently affecting its activity, according to the partial pressure under which the gas acts. De Saussure (1), as long ago as 1804, stated that, in an atmosphere containing 8 per cent. Carbon dioxide, the growth of peas was less than in air; Böhm (2), in 1873, found that roots ofPhaseolus multiflorus , after 17 days’ exposure, exhibited successively less elongation in partial pressures of 2, 5, 10, and 14 per cent. Carbon dioxide respectively, the temperature ranging between 17° and 19° C.; in each percentage named the growth was progressively less than in normal air. Montemartini (3), in 1892, working with roots ofPisum , found 7 per cent. and upwards to depress growthactivity. Chapin (4), in 1902, found the growth of roots ofPisum sativum andVicia sativa to be diminished by 5 per cent., and arrested by 25 to 30 per cent. and upwards. Growth of the stem in the same plants was diminished by 15 per cent., and completely inhibited by 22 to 25 per cent. Experiments conducted by one of us, in conjunction with Professor Farmer, have proved that seedling peas may be kept in an atmosphere containing 20 per cent. carbon dioxide for 14 days without losing the power of renewed growth when placed in air. It is interesting to note that, in many of these plants, the plumule was destroyed, although the main root continued to grow, growth being carried on by shoots arising in the axils of the cotyledons. Brown and Escombe (5) grew plants in increased partial pressures of carbon dioxide. The anatomy of these plants was investigated by Farmer and Chandler (6), who found the growth of the aërial parts to be diminished, while root-growth was apparently unaltered. Ewart (7) observed that carbon dioxide stops protoplasmic steaming, but he does not state the percentage employed in his experiments.