Figure 2.

Total C fixation and ¹⁴C retention, export, and partitioning in major intermediates during a 2-h ¹⁴CO₂ feeding of the source leaf of pea (A, D, G, and J), cucumber (B, E, H, and K), and maize (C, F, I, and L) under 35 Pa CO₂, 21 kPa O₂, and 25°C. Cumulative net C fixation (dashed line in A, B, and C) was calculated from IRGA data, whereas ¹⁴C retention in the leaf was measured both nondestructively by monitoring ¹⁴C with a GM detector continuously (solid line in A, B, and C) and in a parallel set of leaves by destructive analysis (•). Export (dotted line in A, B, and C) was estimated as the difference between total fixation (dashed line) and ¹⁴C retention in the leaf (solid line). D, E, and F show partitioning of total ¹⁴C in the ethanol-soluble fraction (▴), the total sugar fraction (•), and in starch (▪). G, H, and I, Partitioning of total ¹⁴C. J, K and L, Specific activity of the major sugars: Suc (○), raffinose (Raf, ▵), and stachyose (Stac, □). Each point is the average of at least four leaves on four different plants, and each error bar represents the se of the mean.