Effect of auxins on the auxin transport system in coleoptiles

Summary Within 20 min of its application, auxin enhances the transport processes that move auxin molecules through coleoptile tissue. The effect was observed after treatment with indoleacetic acid and -naphthaleneacetic acid, but not with growth-inactive auxin analogues.     

Impedance analysis of bio-fuel cell electrodes

To determine the criteria for the selection of an electrode suitable for a bio-fuel cell (BFC), five electrodes, i.e. silver, aluminum, nickel, stainless steel and carbon fiber cloth were investigated. The performance of the BFC according to the electrode material, including the generated voltage, current density and power density was observed. These results show that the materials used for constructing the electrodes affect the performance of the BFC. An impedance analysis was used to describe the characteristics of the electrodes in the solution. Equivalent circuits of each component such as solution, electrodes-solution interface and electrode were determined from the impedance data. The constant-phase element (CPE) model was applied for data analyzing. It was found that stainless steel, nickel and aluminum behaved like a polarized electrode which has a high electrode-solution interfacial impedance, while carbon fiber cloth and silver had a low impedance like a non-polarized electrode. The impedance data indicated that a higher interfacial impedance will result in a higher loading effect. The results can be summarized that the carbon fiber cloth electrode offers a good electron transfer in the system and thus supplies higher power to the external load.     

Effect of gravity and centrifugal acceleration on auxin transport in corn coleoptiles

Summary Inversion of corn coleoptile sections resulted in a 10–20% inhibition of basipetal transport of 3-indoleacetic acid (IAA) and a more pronounced inhibition (20–50%) of the transport of 1-naphthaleneacetic acid (NAA).The effect of inversion on basipetal NAA transport was compared in wild-type corn and in the amylomaize mutant which contains smaller and slower sedimenting amyloplasts: the gravity induced inhibition was higher in the wild type coleoptiles (27% versus 9%).In wild type the inhibitory effect on basipetal NAA transport appeared within less than 30 min after inversion; then the effect remained relatively constant over at least 2 hr of transport. When the sections were returned to the upright position the transport rate increased, reaching the level of upright controls within 30 min.An effect of gravity on lateral transport of NAA was also demonstrated and shown to be expressed within 10 min after placing the tissue horizontally.When basipetal transport was tested in the direction of gravity and/or centrifugal acceleration, auxin movement incrased with increasing acceleration. Transport against centrifugal acceleration (10 x g) was less than transport of control sections (inverted at 1 x g).The results agree with the hypothesis that starch statoliths act by a pressure mechanism on the membrane transport system of auxin.