Carbohydrate and amino acid composition in phloem sap of Lolium perenne L. before and after defoliation
2004
Amiard, Véronique | Bertrand, A. Morvan | Cliquet, Jean-Bernard | Billard, Jean-Pierre | Huault, Claude | Sandström, Jonas | Prud'Homme, Marie-Pascale | Department of Ecology and Evolutionary Biology (Faculty of Biology) ; University of Science-Vietnam National Universities | Ecophysiologie Végétale, Agronomie et Nutritions (EVA) ; Université de Caen Normandie (UNICAEN) ; Normandie Université (NU)-Normandie Université (NU)-Institut National de la Recherche Agronomique (INRA) | Swedish University of Agricultural Sciences = Sveriges lantbruksuniversitet (SLU)
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Show more [+] Less [-]English. This study investigated leaf exudates collected in a 5 mmol litre-1 EDTA solution as predictors of sugar content of phloem sap obtained through excised aphid (Rhopalosiphum padi) stylets, and analysed the effect of defoliation on the amino acid and the carbohydrate composition in the phloem sap of Lolium perenne (cv. Bravo). Results indicate that leaf exudates obtained from leaves devoid of petiole might not be relevant predictors of carbohydrate content of pure phloem sap. Sucrose was the dominating carbohydrate, accounting for 93% of the total soluble sugars in the phloem sap. Myo-inositol, glucose, and fructose were present in trace amounts, while fructans, raffinose, and loliose have never been detected. Predominant amino acid in the phloem sap was glutamine followed by glutamate, aspartate, and serine. Phloem sap component concentration declined during the first hours following defoliation. Sucrose was the main sugar transported in the phloem sap of L. perenne, despite the fact that the product of fructan degradation was fructose and not sucrose. The results are discussed in relation with the physiological mechanisms that contribute to plant recovery after defoliation.
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