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Doctorat
États-Unis
1965/1969
A BIOCHEMICAL INVESTIGATION OF CALLUS TISSUE IN THE SAGUARO CACTUS (CARNEGIEA GIGANTEA ((ENGELM.)) BRITT. & ROSE)
Titre : A BIOCHEMICAL INVESTIGATION OF CALLUS TISSUE IN THE SAGUARO CACTUS (CARNEGIEA GIGANTEA ((ENGELM.)) BRITT. & ROSE)
Auteur : Caldwell, Roger L.
Université de soutenance : University of Arizona
Grade : Doctor of Philosophy (PhD) 1966
Résumé
The tallest cactus in the United States, the saguaro,
is restricted to southern Arizona in this country. When
the saguaro is wounded, either mechanically (knives, rocks)
or naturally (birds, wind), it responds by forming a hard
tissue layer (callus) around the injured area. Paper and
thin layer chromatographic analyses together with ultraviolet
spectral analysis of saguaro callus extracts indicated
the presence of several phenolic acids. Among these
were : 4-hydroxybenzoic acid, 3,4-dihydroxybenzoic acid,
and 3-methoxy-if-hydroxybenzoic acid. Following the same
procedure, extracts of the pulpy cortex indicated the
presence of 4-hydroxycinnamic acid, 3,4-dihydroxycinnamic
acid, and 3-methoxy-4-hydroxycinnamic acid. One flavonoid,
quercetin, and a second unidentified flavonoid were found
to occur in the callus. There was apparently no flavonoid
content in the vascular elements of the cactus, the woody
ribs.
Although no structural identification of alkaloids
was attempted, chromatographic analysis of the callus,
the ribs, and the intermediate pulpy area indicated the
presence of at least five alkaloids. Previously, only one
alkaloid, carnegine, had been found in the saguaro.
Chromatographic analysis of the intermediate pulpy
cortex indicated the presence of a glycoside of 4-hydroxybenzoic
acid. This glycoside was also found in the "slime
flux" of a decomposing saguaro (decomposition due to bacterial
necrosis). In addition, dopamine (3,4-dihydroxyP-phenylethylamine)
was shown to occur as the major
phenol in the pulpy cortex. The concentration of dopamine
increased markedly in areas of the cactus that were
wounded.
The high lignin content (30.4$) of the callus may
result from hormonal influence of dopamine on early
lignin precursors. Dopamine as a melanin precursor may
also play an important role in the wound metabolism, as
a temporary response. A plausible mechanism for the formation
of callus tissue is given.
Mots clés : Cactus — Diseases and pests. ; Saguaro — Diseases and pests.
Page publiée le 20 février 2016, mise à jour le 20 décembre 2016