Carbohydrate and amino acid composition in phloem sap of Lolium perenne L. before and after defoliation

2004 ◽  
Vol 82 (11) ◽  
pp. 1594-1601 ◽  
Author(s):  
Véronique Amiard ◽  
Annette Morvan-Bertrand ◽  
Jean-Bernard Cliquet ◽  
Jean-Pierre Billard ◽  
Claude Huault ◽  
...  

Carbohydrate and amino acid composition of phloem sap was studied in the grass Lolium perenne L., before and after defoliation. Leaf exudate was collected in a 5 mmol·L–1 EDTA solution from cut leaf blades or stubble, and phloem sap was obtained through excised aphid (Rhopalosiphum padi L.) stylets. 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 Lolium 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.Key words: fructan, sucrose, loliose, defoliation, phloem sap, amino acids.

2011 ◽  
Vol 62 (3) ◽  
pp. 198 ◽  
Author(s):  
Tatjana Balint ◽  
Zdenko Rengel

There is little information on amino acid composition of xylem and phloem sap in canola genotypes differing in use efficiency of nitrogen (N) and/or sulfur (S). Four canola genotypes with either high or low N- and/or S-use efficiency indices were grown in a glasshouse using deficient or adequate N and/or S supply. Xylem sap was obtained by vacuum extraction 46 days after sowing. Phloem sap was collected via bleeding from the petioles of the maturing siliques 120 days after sowing. Among the genotypes, Wesway (N-use efficient) had the highest concentrations of total N, glutamine (235 mmol/L), and asparagine (14 mmol/L) in the xylem sap in the vegetative stage. In contrast, genotype Westar (classified previously as N-use inefficient) had the highest concentrations of most amino acids in the phloem sap among genotypes grown at deficient N supply. Compared with the other tested genotypes, Surpass 402 CL (S-use efficient) had a higher concentration of S, and Karoo (S-use inefficient) had higher concentrations of glutamate and methionine, in the xylem sap in the vegetative stage. Similarly, Karoo had a higher concentration of methionine under adequate S supply and of glutamate under deficient S in the phloem sap at maturity. In conclusion, in canola phloem sap, the most important amino acid for N transport is glutamine, and for S transport methionine and the glutathione-precursor glutamate. It does not appear there is a relationship between differential N- or S-use efficiency of canola genotypes and the concentration of N- or S-transporting amino acids in the phloem sap.


Radiocarbon ◽  
1995 ◽  
Vol 37 (2) ◽  
pp. 319-330 ◽  
Author(s):  
R. E. Taylor ◽  
P. E. Hare ◽  
Christine A. Prior ◽  
Donna L. Kirner ◽  
Lijun Wan ◽  
...  

A series of 14C determinations have been obtained on hair samples principally from Holocene contexts that have been variously pretreated to examine different means of removing potential contamination. SEM photomicrographs have documented hair surfaces before and after different pretreatments. Amino-acid composition, C/N ratios and δ13C values have been obtained to biochemically characterize these samples and provide baseline data for future comparisons with less well-preserved samples. Our data support the view that appropriately pretreated hair samples can provide accurate 14C age determinations.


1990 ◽  
Vol 92 (1) ◽  
pp. 222-226 ◽  
Author(s):  
Jens Weibull ◽  
Fredrik Ronquist ◽  
Sture Brishammar

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