. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. PLANT HORMONES, GROWTH, RESPIRATION 301 THE ROLE OF ORGANIC ACIDS IN GROWTH Some years ago Commoner and Thimann (1941) found that the inhibition by iodoacetate is prevented by malate, succinate, fumarate and pyruvate. More recently we have confirmed this and refined the technique of such experiments. Isocitrate has a similar effect; so also, unexpectedly, do maleate and malonate. The growth system behaves in this respect like succinic dehydrogenase, which has been shown by Hopkins, Morgan and Lutwak-Mann (1938) to be "p
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. PLANT HORMONES, GROWTH, RESPIRATION 301 THE ROLE OF ORGANIC ACIDS IN GROWTH Some years ago Commoner and Thimann (1941) found that the inhibition by iodoacetate is prevented by malate, succinate, fumarate and pyruvate. More recently we have confirmed this and refined the technique of such experiments. Isocitrate has a similar effect; so also, unexpectedly, do maleate and malonate. The growth system behaves in this respect like succinic dehydrogenase, which has been shown by Hopkins, Morgan and Lutwak-Mann (1938) to be "protected" against iodoacetate by these acids. However, while maleic and malonic acids bring the growth rate in presence of iodoacetate back to normal, they have no further effect; malate, succinate, fumarate and isocitrate bring the growth rate considerably above normal (Fig. 5). In other words these acids accelerate growth. There are thus two phenomena to be distinguished: protection against iodoacetate, and promotion of growth. Maleate and malonate, which protect the SH group against iodoacetate, do not promote growth, and indeed in higher concentrations ( M) actually inhibit it. Growth promotion is limited to the acids mentioned above, with the. 40 80 TIME IN MINUTES 120 160 200 240 FIGURE 4. The respiration of sections from 72-hour-old coleoptiles in indole-acetic acid 1 mg., sucrose 10 gins., per liter. Two experiments are shown; the uppermost curve being the controls in each case. The inhibitors were added at the arrow, in concentrations which cause 50 per cent decrease in growth. As: arsenite ;5 M As,O3. IODA: ^ M iodoacetamide. CIHgB : ;5 M parachloromercuribenzoate. PhHgCl: M phenyl-mercuric Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Marine Biolog
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