• Journal of Life Science
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• v.16 no.5
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• pp.859-865
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• 2006

When thin slits (e.g., $1mm{\times}10mm$) of maize (Zea mays) coleoptiles were floated on a buffer, they spontaneously curved outward because of unbalanced tissue tension between inner and outer faces. Exogenously applied auxin induced inward curvature of the thin strip of the maize coleoptile in a dose-dependent manner. This bioassay system was used to screen endogenous substances that work together with auxin. In methanol extract of maize coleoptiles including the leaves inside, Active fractions that promote the auxin-induced inward curvature of maize coleoptile slices were found. The curvature-enhancing activity of the extract was not related to energy supply. The active substances were adsorbed to $C_{18}$ cartridges even at pH 10 and eluted in two fractions by 50% and 80% methanol. These substances were named as Curvature-Enhancing Factor-1 (CEF-1) and Curvature-Enhancing Factor-2 (CEF-2), respectively. The CEF-2 was resolved on a reversed phase $C_{18}$ column by HPLC.

• Journal of Plant Biology
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• v.19 no.2
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• pp.41-44
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• 1976

Ethylene was found to reverse the direction of gravity-induced lateral auxin transport and to cause an accumulation of auxin in the physically upper sides of horizontally placed pea shoots. The pea shoot displayed a slightly positive (downward) geotropic curvature in the presence of applied ethylene. Golgi bodies were found to be distributed preferentially in the bottom halves of cells as against the top halves following geotropic stimulation, and this pattern of intracellular distribution of dictyosomes was also reversed by ethylene treatment. Intracellular displacement of amyloplsts as a result fo geotropic induction was not reversed by the action of ethylene. In view of a positive correlation between the direction of auxin movement and the displacement patern of dictyosomes, it is suggested that the Golgi bodies are involved in the perception of gravity and/or subsequent redistribution of auxin or differential elongation in geotropism.

• Journal of Plant Biology
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• v.37 no.3
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• pp.257-262
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• 1994

The tomato (Lycopersicon esculentum Mill.) mutant diageotropica (dgt) lacking normal gravitropic response is known to be less sensitive to auxin compared with its isogenic parent VFN8. Straight growth as well as ethylene production in response to added auxin in hypocotyl segments of dgt was negligible. However, there was no significant difference between the two genotypes in auxin transport in petiole segments and its inhibition by the phytotropin N-1-naphthylphthalamic acid(NPA). Kinetic parameters of NPA binding to microsomal membranes were also non-distinguishable between the two. Its petiolar explants treated with ethylene developed epinastic curvature with the magnitude of response increased about 3 folds over non-mutant wild type. Ethylene-induced epinasty in both dgt and VFN8 was nullified by treatment of explants with the ethylene autagonist 2,5-norbonadiene. Lateral transport of 3H-IAA toward the upper side of ethylene-treated petioles in dgt, however, was not significantly more pronounced than in VFN8, the implications being that auxin sensitivity in the mutant was restored, or even rised above the wild type, by ethylene.

• Korean Journal of Plant Tissue Culture
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• v.22 no.6
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• pp.345-350
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• 1995

Root gravitropism was investigated in the pea (Pisum sativum L.) mutant ageotropum lacking normal gravitropic response. Exogenous ethylene treatment inhibited gravitropic response in the normal (wild type) pea rook, but had no significant effect to restore the unresponsiveness in the mutant Neither inhibitors of ethylene biosynthesis nor antagonists of ethylene action were able to bring about the development of gravioopic curvature in the ageotropum roots. Auxin action seems to be normal since asymmetric application of agar blocks containing auxin to the mutant roots caused normal gravitropic response to occur. Endogenous as well as auxin-induced ethylene production in tissue segments of the mutant root was about equal to that of the wild type. However no appreciable lateral transport of labeled auxin was observed in glavistimulated mutant roots whereas typical auxin asymetry was apparent in the wild type roots under the same conditions. It is concluded that the mutant has a defect in either gravity perception or its transduction, but not in the effector system involving auxin action.

• The Korean Journal of Mycology
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• v.21 no.2
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• pp.112-119
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• 1993

Various microorganisms secreting plant growth regulators were screened from the 100 microbial isolates including bacteria, actinomycetes and fungi. The isolates showing distict influence on the plant growth were identified as Aspergillus niger. The germinations of Raphanus and Cucubis seeds were completely inhibited by the culture filtrates of A. niger KK, A. niger KKS and A. niger ATCC 9462. The culture filtrates of the three strains also inhibited the formation and development of roots and hypocotyls of Raphanus. The culture filtrates of A. niger ATCC 26550 induced the hypocotyl curvature of Raphanus like plant hormone-auxin and at the same time caused the necrosis of the whole leaves.