Phaseolus petioles

Measurements and calculations of velocities, densities, and intensities of transport to characterize hormone translocation usually imply that these quantities be constant and that the hormone moves in a stream. They do not, however, allow for degradation and/or immobilization, i.e., leakage of molecules out of the stream, to take place. Yet such phenomena do take place, and do vary with time and distance from the hormone source. Variations in the density of mobile auxin have been demonstrated even within short transport sections (e.g., Kaldewey 1963 in Fritillaria axes Newman 1965, 1970 in Avena coleoptiles Kaldewey and Kraus 1972 in Gossypium seedlings Kaldewey etal. 1974 in Pisum internodes Kaldewey 1976 in Tulipa axes). The commonly observed decline of mobile auxin as a function of distance from the auxin source indicates that not all auxin molecules move with the same velocity. The same conclusion may be drawn from the tpyical initial gradual increase of hormone flux into basal receivers which occurs before linearity of the time course is reached (e.g., Hertel 1962, Hertel and Leopold 1963, de la Fuente and Leopold 1973 in Helianthus hypocotyls McCready and Jacobs 1963 a, b, in petioles and Smith and Jacobs 1968 in hypocotyls of Phaseolus de la Fuente and Leopold 1966 in Coleus internodes Thornton and Thimann 1967 in Avena coleoptiles Greenwood and Goldsmith 1970 in Pinus embryonic hypocotyls Wilkins and Cane 1970, Wilkins etal. 1972 and Shaw and Wilkins 1974 in Zea roots Kaldewey et al. 1974 in Pisum internodes Tsurumi and Ohwaki 1978 in Vida roots). 

Black MK, Osborne DJ (1965) Polarity of transport of benzyladenine, adenine and indole-3-acetic acid in petiole segments of Phaseolus vulgaris. Plant Physiol 40 676-680 Bollag JM, Galun E (1966) Distribution of labelled indolyl-3-acetie aeid in intact cucumber plants. Nature 211 647-648... 

Jacobs WP, McCready CC, Osborne DJ (1966) Transport of the auxin 2,4-dichlorophen-oxyacetic acid through abscission zones, pulvini, and petioles of Phaseolus vulgaris. Plant Physiol 41 725-730... 

McCready CC (1963) Movement of growth regulators in plants. I. Polar transport of 2,4-dichlorophenoxyacetic acid in segments from petioles of Phaseolus vulgaris. New Phytol 62 3-18... 

McCready CC, Jacobs WP (1963 a) Movement of growth regulators in plants. II. Polar transport of radioactivity from indoleacetic acid- C and 2,4-dichlorophenoxyacetic acid- C in petioles of Phaseolus vulgaris. New Phytol 62 19-34 McCready CC, Jacobs WP (1963 b) Movement of growth regulators in plants. IV. Relationship between age, growth, and polar transport in petioles of Phaseolus vulgaris. New Phytol 62 360-366... 

Osborne DJ, Mullins MG (1969) Auxin, ethylene and kinetin in a carrier-protein model system for the polar transport of auxins in petiole segments of Phaseolus vulgaris. New Phytol 68 977-991... 

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