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The role of plant hormones and carbohydrates in the growth and survival of coppiced Eucalyptus seedlings (1982)

Taylor, J. S. ; Blake, T. J. ; Pharis, R. P.

Oxford, UK : Blackwell Publishing Ltd

Physiologia plantarum 55 (1982), S. 0

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ISSN: 1399-3054

Source: Blackwell Publishing Journal Backfiles 1879-2005

Topics: Biology

Notes: Depending on the species, coppicing (decapitation) may promote vigorous growth (Eucalyptus camaldulensis Dehn), or cause rapid senescence and death (Eucalyptus obliqua L'Herit). In seedlings of the latter species, the presence of a small upwardly directed shoot on the decapitated stump prevents or delays decline. Coppiced seedlings of E. camaldulensis and E. obliqua, with and without a remaining shoot, were analyzed for starch and soluble sugars (with the anthrone method), gibberellin-like substances (GAs) and cytokinin-like substances (by bioassay), and ethylene (by gas-liquid chromatography) before and after decapitation.Levels of soluble sugars declined similarly in both varieties of eucalypts, and starch reserves appeared adequate for sprouting, and did not diminish following decapitation of the susceptible species.Decapitation did not markedly alter the relatively high amounts of GAs in roots and shoots of E. obliqua, the susceptible species, although increased levels of Gas were observed in the stumps of seedlings left with 1 shoot after decapitation. The overall levels of GaS were relatively low in the roots and stems of the resistant E. camaldulensis, but higher in the shoots. Marked qualitative changes in GAs with decapitation were apparent in the shoots of E. camaldulensis. A single major GA peak occurred prior to decapitation but afer decapitation several additional peaks of GA-like activity appeared.Cytokinin-like activity was initially low in all tissues, but increased dramatically in stump and shoot tissue following decapitation. Increases ranged from approximately 5-fold (stump tissue of either species, minus-shoot treatment) to approximately 40-fold (shoot tissue of the resistant E. camaldulensis seedlings left with 1 shoot). In both E. camaldulensis and E. obliqua ethylene production increased to a peak 7 days after decapitation provided a shoot had been retained. This ethylene peak precedes a marked upturning of the retained shoot, and was not present in the stumps of totally decapitated seedlings. For totally decapitated seedlings ethylene evolution in E. obliqua (the susceptible species), but not E. camaldulensis (the resistant species), had ceased by 15 days.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1111/j.1399-3054.1982.tb04522.x

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Changes in endogenous hormones in apple during bud burst induced by defoliation (1984)

Taylor, J. S. ; Pharis, R. P. ; Loveys, B. ; [et al.]

Springer

Plant growth regulation 2 (1984), S. 117-134

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ISSN: 1573-5087

Keywords: Abscisic acid ; apple ; bud burst ; cytokinins ; defoliation ; gibberellins ; tropical horticulture

Source: Springer Online Journal Archives 1860-2000

Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition

Notes: Abstract Under the tropical conditions of East Java, terminal buds of apple burst at any time of the year in response to removal of the subtending leaves. Following two such defoliations, two weeks apart on separate trees, there was a decrease in abscisic acid (ABA), a three-fold increase in gibberellin-like substances (GAs) and only a slight increase in cytokinin-like substances (CKs) in the apex tissue of closed buds. These changes preceded bud opening and the associated increases in fresh and dry weight, and may be causally related to bud burst. In open buds (i.e. young expanding leaves) the concentration of CKs was greater, and the concentrations of ABA and GAs less, than the concentrations in closed buds. As the leaves expanded, ABA increased and GAs and CKs decreased in concentration. The decrease in concentration of GAs and CKs, however, was due to the rise in dry weight of the expanding tissue; the amounts of all three hormones (per apex) increased. During bud burst there was a concurrent decrease in the CKs of subtending stems, suggesting a transfer into the expanding bud tissues. Removal of the old leaves by defoliation may remove the source of ABA and allow the amount of GAs in the apex to rise, bud burst following. Stem CKs may be utilized in the expansion of the new leaves in the bursting buds.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00024860

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