IFEVA   02662
INSTITUTO DE INVESTIGACIONES FISIOLOGICAS Y ECOLOGICAS VINCULADAS A LA AGRICULTURA
Unidad Ejecutora - UE
artículos
Título:
Metabolic responses to red / far-red ratio and ontogeny show poor correlation with the growth rate of sunflower stems
Autor/es:
MAZZELLA, M.A.; ZANOR, M.I.; FERNIE, R.A.; CASAL, J.J
Revista:
JOURNAL OF EXPERIMENTAL BOTANY
Referencias:
Año: 2008 vol. 59 p. 2469 - 2477
ISSN:
0022-0957
Resumen:
In sparse canopies, low red to far-red (R/FR) ratiosreach only vertically-oriented stems, which respondwith faster rates of extension. It is shown here thatthis signal also promotes stem dry matter accumulationin sunflower (Helianthus annuus) but not inmustard (Sinapis alba L.). Physically blocking internodeextension growth also blocked internode recoveryof labelled carbon fed to the leaves, indicating thatincreased carbon accumulation is partially a consequenceof increased extension growth in sunflower.However, low R/FR also promoted carbon accumulationin the lower section of the internode, whereextension growth was unaffected. Although the levelsof many soluble metabolites and of cell-wall carbohydratesincreased in the stem in response to low R/FR,allowing conservation of their concentration, sucrosewas present at a lower concentration under low R/FR.This change is anticipated to favour carbon unloadingfrom the stem phloem. Low R/FR also reduced thelevels of selected fatty acids, fatty acid alcohols, andsterols. Compared with the lower section, the uppersection of the internode showed higher levels oforganic acids, amino acids, fatty acids, and sterols. Itis concluded that the promotion of stem extensiongrowth by low R/FR ratios causes increased dry mattergain in sunflower internodes by a mechanism that islargely independent of changes in metabolism, since,whilst both low R/FR and ontogeny alter the metabolicprofile, the changes do not correlate with the observedgrowth responses.