Monday, November 13, 2006
67-3
Tassel Development Events Leading to Pollen Production: A Timeline.
Dean Tranel, Pioneer Hi-Bred International, Inc., Pioneer Hi-Bred Int'l Inc., Po Box 85 7301 NW 62nd Ave., Johnston, IA 50131-0085, Allen Knapp, Iowa State Univ., Agronomy Dept., Ames, IA 50011-1010, and Antonio Perdomo, Pioneer Hi-Bred International Inc., 6900 NW 62nd Ave., Johnston, IA 50131.
Establishing the timing of maize male inflorescence developmental events is critical to understanding the affects of stress on tassel development and pollen production. Therefore, critical events of tassel and pollen formation were characterized in relation to plant development. Two inbreds, Inbred A (103 d relative maturity (RM)) and Inbred B (RM 113) were grown under controlled greenhouse conditions. Every two days, three plants per inbred were dissected in order to relate events leading to pollen production to plant development. The duration from tassel initiation to completion of pollen meiosis was longer for Inbred B then for Inbred A. Tassel initiation occurred from fourth leaf stage, six leaf tips (V4:T6) to V5:T7. Branch meristems appeared from V4:T7 to V6:T9. Spikelet-pair primordia appeared from V5:T7 to V7:T10, while sessile spikelets differentiated from V5:T9 to V8:T12. Lower floret initiation occurred from V6:T11 to V8:T13. However, most lower florets were initiated within a 60 heat unit period across the tassel. For a given spikelet-pair, florets formed in the pedicellate spikelet only slightly prior to the sessile spikelet. Anthers were visible within 30 heat units of floret development. After anther formation, pollen mother cells are produced which then enter meiosis. Pollen cells entered meiosis approximately 90 heat units after anther initiation, and pollen meiosis occurred from V9:T14 to V12:T15. This information provides a reference for when events leading to pollen formation occur for two inbreds of differing relative maturities. Of course, other genetics or environmental conditions may alter these developmental relationships.
Handout (.pdf format, 141.0 kb)