Figure 8.

Effect of seed oxygen supply on the distribution of ¹¹C-labeled assimilates in a wheat plant 20 DAH. A, Transport toward the ear (black line) and lower culm (gray line) was measured when the oxygen concentration of the air around the ear was decreased from 21% to 8% (indicated by the arrow). B, The ear of the same plant as used in A was kept at low oxygen overnight. The next day, a new ¹¹C treatment was started. Oxygen around the ear remained at 8% during the first 5 h of ¹¹C-labeling. Then oxygen was shifted back to 21% (the arrow marks the 8% oxygen treatment). C, The changes in phloem transport induced by a 2-h treatment of low oxygen around the ear. D, Effect of high oxygen around the ear, in a plant trimmed at mid-seed filling (20 DAH) of all leaves except for the flag leaf. Note the reduced transport of label to the ear, and increased transport to the lower stem compared to an untrimmed plant of the same age shown in Figure 7D. Treatment with high (40%) oxygen is indicated by the arrow.