| Abstrakt: |
Maize (Zea maysL.) growing in the field was labeled with 14CO2at four leaf positions 15 to 18 days after flowering. On four occasions after labeling, entire plants were harvested and 14C in several plant fractions was analyzed by liquid scintillation spectroscopy to reveal patterns of translocation within the plants, losses of 14C by respiration, and patterns of mobilization and redistribution of 14C among and within organs. The first and third leaf blades above the ear (+1 and +3, respectively), and the first blade below the ear (–1), exported 14C mainly kernels of the developing ear. Among these three leaf blades, the extent of export of 14C was more rapid from upper positions than from lower ones. Movement of 14C from the fifth leaf blade (–5) below the ear was much slower than that from the upper three blades, but kernels of the developing ear ultimately became the principle sink for 14C exported by this blade. Compared with the upper three leaf blade positions, however, appreciable label from –5 accumulated in the lower stem and roots. Labeling plants bearing partly‐fertilized ears caused a large accumulation of 14C in the stem, roots and to a lesser extent, husks, compared with completely‐fertillzed controls. About 20% of the 14C assimilated by the +1, +3, and –1 blades was lost by respiration in the 5 weeks following labeling. During the same interval, nearly 70% of the 14C assimilated by the –5 blade was lost by respiration. Approximately half of the carbon assimilated by +3, +1, and –1 blades was translocated directly to kernels within 24 hr after assimilation. A similar quantity of label assimilated by +3, +1, and –1 blades was deposited in cobs and husks within 24 hr after assimilation. Estimates of redistribution of label within the plants suggest that 60 to 80% of the 14C accumulated in kernels between days 1 and 35 following labeling was derived from 14C originating in upper leaves and deposited in the cob and husk within 24 hr. |
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