The Relationship Between Growth and Metabolism in the Oat Seedling

Abstract

DURING THE course of an earlier investigation, Albaum and Commoner (19,1<1) were able to show that iodoacetic acid inhibited the growth of intact oat seedlings. This inhibition, however, did not appear immediately, but was manifest only after the seedlings had been subjected to the treatment for several days. At the time it was assumed that this lag in response might be due to difficulty in penetration of the iodoacetate. Subsequent experiments with other respiratory poisons and some stimulants, however, made this explanation highly unlikely. These new experiments indicated that iodoacetate, and some of the respiratory stimulants used, produced no immediate effects on growth because the .early growth stages are probably under the control of metabolic processes insensitive to these substances, but with time new metabolic mechanisms appear which respond to the addition of these substances. This paper amplifies the results of some of these later experiments and presents more complete evidence establishing the operation of at least two distinct respiratory mechanisms controlling the growth of the oat seedling.:MATERIAL AND METHoDs.-Grains of Avena sativa L. var. Black Norway, similar to those used in earlier experiments were hulled, soaked in distilled water for two hours in the light, and germinated in the dark for twenty-four hours at 27°C. After germination, the grains were planted in beakers in contact with moist filter paper, as described in an earlier paper (Kaiser and Albaum, 1939), to which test solutions had been added. The plants were then allowed to continue their growth in the dark at the same temperature. At regular intervals, the coleoptiles were measured to the nearest millimeter. Coleoptile length was used as an index of growth. All figures reported are the averages of at least twenty plants. The test solutions, iodoacetic, fumaric, pyruvic, succinic, malic, maleic and malonic acids, and sodium azide (all Eastman Kodak) were made up in distilled water and adjusted with a Beckmann pH meter to pH 6.0 with KOH at the beginning of each experiment. The pH of these solutions did not change appreciably during the course of the experiments.All measurements on oxygen uptake were carried out in a Warburg respirometer at 26°C. Those experiments not performed on intact embryos (prepared by dissection from seedlings; see below) were carried out on extracts made up in the following way: Grains were removed from beakers in which they had been grown, 24, 48, 72, 96 and 120 hours after soaking. The embryos were carefully dissected from groups of fifty seedlings, ground in sand in 2 cc. of

Cytochrome Oxidase in Higher Plants

“…From wheat embryo Goddard (1944) obtained cytochrome c which had the same catalytic properties as that from an animal source. The results obtained by Okunuki (19390,6) and ourselves (1939) have been independently confirmed by several authors with other plant tissues: barley embryos (James, 1946;Merry & Goddard, 1948); wheat embryos (Brown & Goddard 1941;Goddard, 1944); oats (Albaum & Eichel, 1943); potato (Levy & Schade, 1948). Recently, Rosenberg & Ducet (1949) have found that cytochrome oxidase is present in preparations of chloroplasts; the presence of cytochrome c in the leaves of plants was described by Scarisbrick (1948) and Hill & Scarisbrick (1951).…”

Phosphorus Transformations During the Development of the Oat Embryo

“…This enzyme also appears to increase with time. The marked increase in easily hydrolyzable (presumably "energy-rich") phosphorus at about 72 hours makes it seem possible that this compound is intimately associated with the rapid utilization of sugar, coleoptile elongation, increase in dry weight, rapid nitrogen transport (Albaum, Donnelly and Korkes, 1942), increased protein synthesis (Albaum and Cohen, 1943), heightened catalase activity and Data are presented which show that the total phosphorus of the oat embryo increases with time at the expense of the phosphorus of the endosperm.…”

“…Within the barium-insoluble fraction there is marked increase in phosphoglyceric acid, hexose diphosphate and labile, readily hydrolyzable phosphorus which may be associated with a compound of the adenosine triphosphate variety. Phytic acid which makes up the largest part of this fraction in dehydrogenase activity (Albaum, Donnelly and Korkes, 1942), all of which are known to occur at about this time.…”

The Chemistry and Physiology of Growth

“…Darlington (1944) has recently suggested a similar mechanism. Potter and Albaum (1943) consider viruses to be "misplaced enzymes. "…”