Inhibition of maize endosperm cell division and endoreduplication by exogenously applied abscisic acid

Abseisic acid (ABA) is thought to play a role in inhibiting or aborting kernel growth during water deficit. To test the responsiveness of early endosperm development to ABA concentrations. cylinders containing (+/-)ABA in a buffered agar medium were applied to the apical pericarp surface of kernels on intact, well-watered maize (Zea mays L. cv. Pioneer Brand 3925) plants from 5 to 11 days after pollination (DAP), Endosperm nuclei were analyzed by Bow cytometry to assess effects on cell division and endoreduplication. ABA treatments of greater than or equal to 100 mu M substantially decreased endosperm cell numbers and fresh weight accumulation, but did not affect average cell size. ABA at greater than or equal to 300 mu M decreased the proportion of nuclei in the size classes greater than or equal to 12C, indicating that the rate of transition to endoreduplication status was inhibited, and decreased the progressive advance from 12C to 24C to 48C, indicating that the rate af S-phase cycling of endoreduplicating cells was inhibited. We conclude that cell division was more responsive to ABA concentrations than were endoreduplication or cell expansion growth.