Masami Shimokoriyama

Glucose catabolism during aging and differentiation in hypocotyls ofPhaseolus mungo seedlings

Changes in activities of the glycolytic and pentose phosphate (PP) pathways in glucose catabolism in various parts of the hypocotyls obtained from 4-day-old etiolatedPhaseolus mungo seedlings were investigated by measuring the inhibition rates of respiration by iodoacetate and malonate, and the release of14CO2 from [1-14C]- and [6-14C]glucose. The relative activity of the PP pathway in glucose catabolism was higher in the immature part (Part I) and the aged part (Part V) of the hypocotyls than in the intermediary one (Part III), while the activity of the glycolytic pathway decreased with aging.On a fresh weight basis, the enzyme activities of the glycolytic and PP pathways were higher in Part I than in Parts III and V. On a protein content basis, however, activities of the enzymes of the PP pathway increased with aging and differentiation of the hypocotyls whereas those of the glycolytic pathway decreased. Levels of nicotinamide adenine nucleotides were found to be in the following order: Part I>Part III> Part V for NAD++NADH; Part I>Part V>Part III for NADP++NADPH. The stimulative effect of methylene blue on decreasing the C6/C1 ratio was greater in Part III than in Part I, and No effect was observed in Part V.These data suggest that a decrease in the activity of the glycolytic pathway with aging and differentiation may be due to the decreasing glycolytic enzyme activities and NAD(H) content. The higher activity of the PP pathway in the immature part is attributable to larger amounts of NADP(H) and enzymes of the PP pathway. The greater contribution of the PP pathway to glucose catabolism in the aged part than in the intermediary part seems to results from a more active turnover of NADP and the relatively higher activity of the enzymes of the PP pathway than those of the glycolytic pathway.

On the formation of carthamin in the flowers of Carthamus tinctorius.

Abstract The process of reddening of yellow flower petals of Carthamus tinctorius was biochemically investigated and it was concluded that the process may involve the polyphenoloxidase- or peroxidase-catalyzed oxidation of a leucopigment, i.e. dihydrocarthamin, as a precursor.

Stimulation of Avena Coleoptile Growth by Reduction of Oxygen Supply

SummaryThe growth of Avena sativa L. coleoptiles was accelerated by reduction of the O2 concentration in the surrounding atmosphere. Cell-wall extensibility was increased in close relation to the increase in elongation, 6–8% O2 giving the optimal effect in either case. Growth promotion by reduced O2 concentration and by auxin (indole-3-acetic acid; IAA) were additive, at least at lower auxin concentrations.This response to reduced O2 concentration was also present in sections pretreated with cycloheximide for 2 h, although such sections showed no response to applied IAA. No significant change was observed in auxin transport under reduced O2 supply. It is suggested that the acceleration of cell elongation and the loosening of cell wall by reduced O2 supply are due to a mechanism which is not directly dependent on auxin-induced growth. We propose to designate this acceleration of growth under reduced O2 concentrations as oxygen-sensitive growth.