Table I.

Amino acid determination (% and total content) in phloem sap collected from tobacco leaves of different ages

Amino acids were pooled prior to analysis, which was carried out according to Chaffei et al. (2004). Numbers in parentheses correspond to the amino acid determination (% and total content) in leaf blades, determined as described by Masclaux et al. (2000). Boldface type shows amino acids with higher values as indicated in the text. Values represent the means of analysis on phloem exudates from five independent plants.

Amino AcidsAmino Acids in Phloem Saps
Leaf No. 9Leaf No. 10Leaf No. 13Leaf No. 20Leaf No. 30
Asp %10.09.77.68.48.1
Asn %10.3 (5.2)15.4 (3.7)8.9 (1.8)10.2 (1.2)9.6 (1.8)
Ser %13.910.917.316.27.2
Glu %8.7 (25.5)7.6 (27.7)6.2 (25.3)6.5 (28.8)5.4 (15.3)
Gln %27.9 (17.0)22.1 (14.9)30.3 (12.4)21.9 (10.6)21.8 (14.0)
Pro %7.6 (1.3)9.7 (2.3)12.9 (1.3)21.1 (2.9)34.6 (14.1)
Gly %4.96.92.01.92.5
Ala %4.24.94.03.85.6
Total nmol/mg dry weight109.0 (55.0)65 (41.4)59.0 (43.1)46.8 (29.0)21.5 (51.0)