Cytokinin-Inhibitor Antagonism in the Hormonal Control of α-Amylase Synthesis and Growth in Barley Seed

The effect of cytokinins and gibberellic acid on the inhibition of growth and α-amylase synthesis by germination inhibitors was investigated in intact and embryoless seed halves. The cytokinins, kinetin and benzyladenine, effectively reversed the inhibition of coleoptile growth and α-amylase synthesis by abscisic acid and courmarin in barley seed. An antagonism between cytokinins, kinetin and benzyladenine, effectively reversed the inhibition of coleoptile growth and α-amylase synthesis by abscisic acid and coumarins in barley seed. An antagonism between cytokinins and germination inhibitors was also shown in root growth. Abscisic acid inhibited coleoptile growth to a greater extent than the root growth while the opposite held true in the case of coumarin. The apparent increase in coleoptile growth and α-amylase synthesis by gibberellic acid plus abscisic acid (or coumarins) over abscisic acid (or coumarin) appears to be a result of the overall stimulation of growth and metabolism by exogenous gibberellic acid and probably does not involve an interaction of gibberellic acid with the inhibitors. Gibberellic acid reversed root inhibition to some extent. Abscisic acid inhibition of gibberellic acid induced α-amylase synthesis in the embryoless endosperm was not reversed by excess gibberellic acid or kinetin Cytokinin reversal of inhibition of growth and enzyme synthesis probably depends on some factor(s) in the embryo. Cytokinin reversal of inhibitor action leading to enzymen synthesis and growth may be at the level of genome or at the site protein assembly.     

Proflavine Uptake and Release in Sensitive and Resistant Escherichia coli

Both Escherichia coli B and a proflavine-resistant mutant, E. coli B/Pr, took up the same amounts of proflavine when suspended in buffer containing the dye. In growth media, however, sensitive cells took up more proflavine than did resistant cells. Adding growth media or any one of several constituents of these media, including amino acids, glycerol, pyruvic acid, and metabolizable sugars, to resistant cells that had taken up proflavine in buffer caused them to lose the dye, but had less or no effect on sensitive cells. Certian salts caused an equal release of proflavine from resistant and sensitive cells. Proflavine released from resistant cells by glucose was not changed chemically. The effects of temperature and metabolic inhibitors suggest that proflavine uptake is a passive process but that its release may be an active one, dependent on metabolism. Glucose had more effect on the proflavine binding of E. coli B grown in a minimal medium than on that of cells grown in a complex medium. E. coli B was less susceptible to proflavine when growing in a minimal medium. The effects of other synthetic media on proflavine susceptibility of E. coli B were also studied. Deoxyribonucleic acid and envelopes from sensitive and resistant cells bound the same amounts of proflavine, and no difference was seen in the site of dye binding when sensitive and resistant cells that had taken up proflavine in buffer were sonically broken and fractionated. The results suggest that sensitive and resistant cells are equally permeable to proflavine but differ in the ease with which metabolites cause them to release bound proflavine. So far, however, these differences do not account completely for the ability of resistant cells to grow in high proflavine concentrations.     

Isolation of High-Frequency Recombining Strains from Escherichia coli Containing the V Colicinogenic Factor

The isolation and characterization of high-frequency recombining strains from different Escherichia coli host cells containing either the F factor or the Col V factor are described. The strains (with one exception) formed from three of the V⁺ parents showed the same origin and polarity of transfer (xyl-arg-pro-trp-his-mal). The Hfr strains formed from the one remaining V⁺ and the F⁺ host cells showed a greater variety in their points of origin. In addition, several Hfr strains isolated from V⁺ parents lost the ability to produce colicin V. F_v⁺ segregants of these were isolated, and the F_v factors appeared to retain their preferential site for Hfr formation, but they lacked other propertes controlled by the Col V factor. Chromosomal integration of episomes and its relation to the fertility of F⁺ and V⁺ strains are discussed. Production of colicin V appeared to be uninfluenced by the state of the Col V factor within the cell.     

Physiology of Morphactins: Effect on Gravi- and Photo-response

Plant roots and shoots respond to gravity and light source in a definite way. Thus, there are typical geotropic and phototropic responses for roots and shoots. When seedlings were grown in presence of morphactins, IT 3233 or IT 3456, on a vertical or a horizontal plane, the roots and shoots lost the capacity to respond to gravity or to unilateral light source. This was true for both monocots and dicots. This suggests that basic mechanism (s) of the two tropic responses are the same in the roots and shoots of the two plant groups. The site(s) of action of morphactins is unknown. The reaction (s) controlling geotropism and phototropism may be closely related as morphactins affected both geotropic and phototropic response of the same organ. Indoleacetic acid and gibberellic acid per se did not modify the effect of morphaclins on geotropism. Growth retardation effect of morphactins appears to be controlled by another mechanism.