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Digitale Medien

Auxin-induced assimilate translocation in the bean stem (Phaseolus vulgaris L.) (1987)

Morris, D. A. ; Arthur, E. D.

Springer

Plant growth regulation 5 (1987), S. 169-181

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ISSN: 1573-5087

Schlagwort(e): assimilate translocation ; auxin ; invertase (EC 3.2.1.26) ; Phaseolus vulgaris ; phloem translocation

Quelle: Springer Online Journal Archives 1860-2000

Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft

Notizen: Abstract Decapitation of the fully-elongated fourth internode of Phaseolus vulgaris plants resulted in the disappearance from the internode of soluble acid invertase (EC 3.2.1.26). This loss was prevented by local applications to the internode of indol-3yl-acetic acid (IAA) and, at the point of IAA application, the specific activity of the enzyme increased by up to 3 times its initial value within 48 h of treatment. IAA applications stimulated the acropetal translocation to the internode of 14C-sucrose applied to the subtending (second) trifoliate leaf 30 h after decapitation and the start of the auxin treatment. Labelled assimilates accumulated in the IAA-treated region of the internode. Following decapitation the concentration of hexose sugars in the internode fell and that of sucrose rose substantially, but these trends were reversed by IAA treatment. However, small local accumulations of sucrose occurred at the point of auxin application where tissue concentrations of IAA were greatest (determined using [1-14C] IAA). Considerable quantities of starch were present in the ground parenchyma of the internodes at the start of the experiment but, in the absence of IAA, this was remobilised within 48 h of decapitation. IAA prevented starch loss at and below its point of application to the internode, but not from more distal tissues. Cambial proliferation, radial growth and lignification were stimulated in and below IAA-treated regions of the internode. These observations are discussed in relation to the hormonal regulation of assimilate translocation in the phloem.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1007/BF00024693

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Digitale Medien

Stimulation of acid invertase activity by indol-3yl-acetic acid in tissues undergoing cell expansion (1986)

Morris, D. A. ; Arthur, E. D.

Springer

Plant growth regulation 4 (1986), S. 259-271

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ISSN: 1573-5087

Schlagwort(e): Acid invertase (β-fructofuranosidase) ; auxin ; cell expansion ; Phaseolus vulgaris

Quelle: Springer Online Journal Archives 1860-2000

Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft

Notizen: Abstract The soluble acid invertase activity of young, excised P. vulgaris internodal segments fell when they were incubated in water, and their elongation ceased within 6–7 h. IAA (10 μM) promoted segment elongation and stimulated an increase in the specific activity of acid invertase to a level greater than that originally present. The rate of segment elongation in the presence of IAA was closely and positively correlated with the specific activity of the enzyme. Optimum concentration of IAA for both elongation and stimulation of invertase activity was 10 μM. Concurrent protein synthesis was necessary for these responses to IAA. Segments cut from mature, fully-elongated internodes did not responsd to IAA. Inclusion of Ca2+, vanadate or mannitol in the incubation medium abolished IAA-induced segment elongation but did not inhibit the stimulation of acid invertase activity by IAA. Auxin-induced elongation and acid invertase activity were both substantially increased in the presence of up to 25 mM D-glucose or up to 50 mM sucrose. Inclusion of either sugar in the medium considerably increased tissue hexose concentrations. Under some circumstances cell growth and invertase synthesis may compete for available hexose substrate. It is concluded that IAA-induced promotion of acid invertase in P. vulgaris internodal segments is not simply an indirect consequence of removal of end-product (hexose) during IAA-induced cell growth and that a more direct action of IAA on enzyme turnover is involved.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1007/BF00028169

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