Figure 5.

Time course of the fraction of unlabeled carbon in CO₂, respired by shoots (black symbols) and roots (white symbols) of perennial ryegrass plants during respiration measurements, for plants that were previously labeled for 1 h (triangles) and 24 h (circles). Error bars denote se (n = 4). The dashed line denotes the linear regression for shoots labeled for 1 h (y = 0.83 + 0.48 x, r² = 0.74; see “Materials and Methods”). The regression for the other labeling times was nonsignificant (data not shown).