PHENOL METABOLISM IN RELATION TO DISEASE RESISTANCE OF POTATO TUBER: I. ACTIVITIES OF PHENOL OXIDASE AND SOME ENZYMES RELATED TO GLYCOLYSIS AS AFFECTED BY CHLOROGENIC ACID TREATMENT

Disks of potato tubers, 0.5 mm in thickness, were treated witha mixture of chlorogenic and ascorbic acids. When they werenot washed with water after the treatment, they became brown.Activities of phenol oxidase and glutathione reductase and o-diphenolcontent increased more rapidly in these disks than in untreatedcontrol. Activity of the pentose phosphate pathway was increasedby the treatment, while that of EMDEN-MEYERHOF-PARNAS pathwaywas greatly inhibited. In washed unbrowned disks, the changesin those activities were negligible or smaller than those inthe browned disks, although chlorogenic acid which had permeatedremained in the tissue after washing. Oxidized products of chlorogenicacid and possibly of ascorbic acid may be a trigger in thisalteration in metabolism. Malonate and streptomycin also induced similar effects on thephenol metabolism in the tuber disks. Increases in o-diphenolcontents and in phenol oxidase activity were caused probablyby preferential inhibition of EMDEN-MEYERHOF-PARNAS pathwayand tricarboxylic acid cycle. These results are discussed inrelation to the mechanism of disease resistance of potato tuber. (Received May 6, 1966; )     

EFFECT OF AUXIN ON β-1, 3-GLUCANASE ACTIVITY IN AVENA COLEOPTILE

When the homogenate of Avena coleoptile segments was fractionated, the specific activity of β-1, 3-glucanase was remarkably associated with the cell wall, partly to be released from it by a detergent. The cell wall-bound glucanase activity was increased by the treatment of coleoptile segments with auxin. Only in 10 min of the treatment the glucanase activity and the incorporation of labeled leucine into the proteins were found to be increased in the fraction to be liberated by detergent from the cell wall fraction. These effects of auxin were inhibited by 10 μg/ml cycloheximide.     

Auxin-induced cell expansion in relation to cell wall extensibility

Decapitation of 30 mm oat coleoptiles, which are commonly usedfor growth tests, resulted in a decrease in their elastic extensibility(DE) but not in their plastic extensibility (DP). By auxin treatmentunder osmotic stress, old coleoptile (45 mm) cells showed noincrease in subsequent expansion in water, whereas RNA synthesisin these cells was stimulated just as in young ones. Auxin increasedthe DE of young coleoptile cell walls but not that of old ones.Significant increase of DE occurred in only 10 min, and themaximum level of DE was reached in 15 min of the auxin treatment.An antiauxin (2,4,6-trichlorophenoxyacetic acid), mitomycinC and cycloheximide inhibited auxin-induced increases in expansionand DE (or Rex, reversible extensibility) of young coleoptilecells. (Received July 23, 1968; )