Effects of Phase Transition on the Development of Lateral Buds in Maize

Different lateral bud structures are generated along the main shoot axis in maize ( Zea mays L.). This study was conducted to show how the structural diversity of the lateral buds is generated. The growth and development of lateral buds of three hybrids were investigated under field conditions at Tokyo, Japan, on a silt loam (Andosols). Six plants per hybrid were harvested as each leaf emerged and the morphological features and the length of each lateral bud were determined. We observed in mature plants that the lateral buds consisted of two discrete populations acropetally along the main stem (i) lower lateral buds that remained in a vegetative state, and (ii) upper lateral buds, including grain‐bearing shoots, that terminated in reproductive organs. Lower lateral buds elongated sequentially up the stem and grew for a specific time interval. The phase transition of the apical meristem to tassel initiation evoked a change in the bud growth pattern. At tassel initiation, the upper lateral buds were still in an incipient state without establishing a complete bud structure. During the reproductive phase that followed, elongation of the upper lateral buds occurred simultaneously. These results suggest that lateral bud growth during the vegetative phase was regulated independently from the reproductive phase during plant development. Lateral buds that are at a certain development state could be responsive to the change in physiological signals during the transition between vegetative and reproductive phase.