Figure 8.

A, Levels of ¹¹C-labeled amino acids (presented as % total ¹¹C activity fixed as ¹¹CO₂) were plotted for the following tissues: load leaf at 10 min postadministration of ¹¹CO₂, load leaf at 90 min postadministration of ¹¹CO₂, and roots at 90 min postadministration of ¹¹CO₂ to leaves. The gross export of ¹¹C-labeled amino acids was calculated from the difference in load leaf activities at 10 and 90 min. Root herbivore treatment manifested in a significant increase in gross export of amino acids from source leaves, as well as in a significant increase in their allocation to roots. B and C, Relative distributions of ¹¹C-labeled amino acids are presented for the load leaf (B) and roots (C) at 90 min postadministration of ¹¹CO₂ and as a function of root herbivore treatment. Treatment increased source leaf levels of [¹¹C]Gln, [¹¹C]Glu, and [¹¹C]Asn. Treated roots showed significantly higher levels of [¹¹C]Gln, as well as lower levels of [¹¹C]Ala and other less-abundant radiolabeled amino acids that were summed together. Where appropriate, statistical significance was denoted as *P ≤ 0.05; **P ≤ 0.01; ***P ≤ 0.001.