Roles of the fructans from leaf sheaths and from the elongating leaf bases in the regrowth following defoliation of Lolium perenne L |
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Authors: | Morvan-Bertrand A Boucaud J Le Saos J Prud'homme M P |
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Institution: | (1) UMR INRA Physiologie et Biochimie Végétales, IRBA, Université de Caen, Esplanade de la Paix, 14032 Caen Cedex, France, FR |
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Abstract: | The study of carbohydrate metabolism in perennial ryegrass (Lolium perenne L. cv. Bravo) during the first 48 h of regrowth showed that fructans from elongating leaf bases were hydrolysed first whereas
fructans in mature leaf sheaths were degraded only after a lag of 1.5 h. In elongating leaf bases, the decline in fructan
content occurred not only in the differentiation zone (30–60 mm from the leaf base), but also in the growth zone. Unlike other
soluble carbohydrates, the net deposition rate of fructose remained positive and even rose during the first day following
defoliation. The activity of fructan exohydrolase (FEH; EC 3.2.1.80) was maximal in the differentiation zone before defoliation
and increased in all segments, but peaked in the growth zone after defoliation. These data strongly indicate that fructans
stored in the leaf growth zone were hydrolysed and recycled in that zone to sustain the refoliation immediately after defoliation.
Despite the depletion of carbohydrates, leaves of defoliated plants elongated at a significantly higher rate than those of
undefoliated plants, during the first 10 h of regrowth. This can be partly attributed to the transient increase in water and
nitrate deposition rate. The results are discussed in relation to defoliation tolerance.
Received: 16 June 2000 / Accepted: 17 October 2000 |
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Keywords: | : Defoliation Elongation (leaf base) Fructan Growth zone Leaf sheath Lolium (defoliation) |
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