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Abstract

This paper is the first published report describing micropropagation of Carlina onopordifolia, using shoot tip and hypocotyl explants. The explants were excised from 10-day-old seedlings and transferred to proliferation medium supplemented with 6-benzylaminopurine (BA; 1.0 or 3.0 mg l-1), kinetin (Kn; 1.0 or 3.0 mg l-1) or zeatin (ZEA; 1.0 or 3.0 mg l-1) in combination with naphthaleneacetic acid (NAA; 0.1 mg l-1). The shoot tips were significantly better than hypocotyls as initial material for shoot regeneration. For shoot multiplication, MS medium supplemented with BA proved superior to the other cytokinins tested. Medium supplemented with 1.0 mg l-1 BA gave the highest shoot propagation frequency (66.9%) and number of shoots per explant (2.5). Single shoots were separated from each other and rooted on MS supplemented with IBA for the whole period of culture, with longor short-pulse IBA application. The highest rooting frequency (84.8%) and root number (18.8) were for shortpulse (1 min) 1000 mg l-1 IBA solution. The higher IBA concentration stimulated callus formation and the development of short roots. The shoots were transferred to MS medium without growth regulators. Survival was highest (54.4%) for the plants from the short-pulse 100 mg l-1 IBA treatment. After 8 weeks of acclimatization the plantlets were removed to field conditions and grew normally.
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Abstract

The full-length cDNA of LeTIR1 gene was isolated from tomato with EST-based in silico cloning followed by RACE amplification. LeTIR1 contained an open reading frame (ORF) 1872 bp long, encoding 624 amino acid residues. The predicted protein LeTIR1 had one F-box motif and eleven leucine-rich repeats (LRRs), all of which are highly conserved in TIR1 proteins of other plant species. Phylogenetic analysis showed that the LeTIR1 protein shared high similarity with other known TIR1 proteins. Both sequence and phylogenetic analysis suggested that LeTIR1 is a TIR1 homologue and encodes an F-box protein in tomato. Semi-quantitative RT-PCR indicated that LeTIR1 was expressed constitutively in all organs tested, with higher expression in stem than root, leaf, flower and fruit. Its expression level was positively correlated with the auxin distribution in stem or axillary shoot, and was induced by spraying exogenous IAA.
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Abstract

Petiole bending in detached leaves of Bryophyllum calycinum was intensively investigated in relation to polar auxin transport in petioles. When detached leaves were placed leaf blade face down, clear petiole bending was observed. On the other hand, no petiole bending was found when detached leaves were placed leaf blade face up. Indole-3-acetic acid (IAA) exogenously applied to petioles was significantly effective to induce and/or stimulate petiole bending when detached leaves were placed leaf blade face down. To clarify the mechanisms of petiole bending in detached leaves of B. calycinum when they were placed leaf blade face down, the effects of application of IAA, ethephon which is an ethylene releasing compound, inhibitors of polar auxin transport such as 2,3,5-tiiodobenzoic acid (TIBA), N-1-naphthylphthalamic acid (NPA) and 9-hydroxyfluorene-9-carboxylic acid (HFCA) and methyl jasmonate (JA-Me) were thoroughly investigated. Ethephon was not effective to enhance petiole bending, suggesting that ethylene derived from exogenously applied IAA does not play an important role in petiole bending in detachd leaves of B. calycinum. This suggestion was strongly supported by the fact that ethephon exogenously applied to petioles in intact plant of B. calycinum had no effect on inducing epinasty and/or hyponasty either (Ueda et al., 2018). Potent inhibitors of polar auxin transport, TIBA and HFCA, and JA-Me were extremely effective to inhibit petiole bending but NPA was not. Almost no petiole bending was observed in excised petiole segments without the leaf blade. Applicaton of IAA to the cut surface of petioles in the leaf blade side strongly promoted petiole bending. Polar auxin transport in excised petioles of B. calycinum was intensively investigated using radiolabeled IAA ([1-14C] IAA). Clear polar auxin transport was observed in excised petiole segments, indicating that auxin allows movement in one direction: from the leaf blade side to the stem side in petioles. When detached leaves were placed only leaf blade face down, transported 14C-IAA was reduced in the lower side of the excised petioles. These results strongly suggest that transport and/or lateral movement of endogenous auxin biosynthesized or produced in the leaf blade are necessary to induce petiole bending in detached leaves of B. calycinum. Mechanisms of petiole bending in detached leaves of B. calycinum are also discussed in relation to polar auxin transport and lateral movement of auxin.
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Abstract

During the research interaction of indole-3-acetic acid (IAA) and methyl jasmonate (JA-Me) in epinasty and/or hyponasty, as well as petiole growth of Bryophyllum calycinum were investigated. Exogenously applied IAA as a lanolin paste was extremely effective to induce epinasty and/or hyponasty accompanied with petiole elongation in intact B. calycinum. Application of IAA around or to the upper side of the petiole was much more effective than that to the lower side, suggesting that petiole epidermal cells on the adaxial side of B. calycinum are more sensitive and/or susceptive to IAA than those on the abaxial one. This is supported by the fact that not only the second curvature but also the first one in B. calycinum was enhanced by application of IAA to the upper side of the petiole. The degree of epinasty and/or hyponasty induced by IAA is strongly related to the increase of petiole growth. On the other hand, JA-Me significantly inhibited IAA-inducing epinasty and/or hyponasty, and petiole growth in intact B. calycinum. When detached leaves with petioles were placed leaf blade face down, clear petiole bending was observed. However, no petiole bending was found when detached leaves were placed leaf blade face up. Exogenously applied IAA to petioles was significantly effective to induce and/or stimulate petiole bending in placing detached leaves of B. calycinum face down but ethephon was not, suggesting that transport and/or movement of endogenous auxin produced in the leaf blade are necessary to induce petiole bending in detached leaves of B. calycinum and that ethylene derived from exogenously applied IAA does not play an important role in epinasty and/or hyponasty, and petiole bending in B. calycinum. The mechanisms of IAA-enhancing and JA-Me-inhibiting epinasty and/or hyponasty, and petiole growth are intensively discussed.
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Abstract

Application of 1-naphthaleneacetic acid (NAA) or 1-aminocyclopropane-1-carboxilic acid (ACC) to maize roots growing in hydroponic solution inhibited root elongation, and increased radial growth, but the responses to those treatments differed in degree. Auxin was more effective than ACC as an elongation inhibitor and root swelling promoter. Whereas NAA fully inhibited elongation and maintained swelling over 48 h, ACC inhibited elongation partially (50%) and only promoted swelling for 24 h. It is well-known that auxin, like ACC, promotes ethylene production, but similar levels of ethylene production reached by means of NAA or ACC treatments did not elicit the same response, the response being always stronger to NAA than to ACC. These results suggest that the effect of auxin on root growth is not mediated by ethylene. Elongation and swelling of roots appear to be inversely related: usually a reduction in elongation was accompanied by corresponding swelling. However, these two processes showed different sensitivities to growth regulators. After 24 h treatment with 0.5 μM NAA or 5 μM ACC, root elongation was inhibited by 90% and 53% respectively, but the same treatments promoted swelling by 187% and 140% respectively. Furthermore, 1 μM ACC was shown to promote inhibition of root elongation without affecting swelling. The ethylene antagonist STS (silver thiosulfate) did not affect elongation in control or NAAtreated roots, but increased ethylene production and swelling. These results indicate that longitudinal and radial expansion could be independently controlled.
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