Effects of Indol-3yl acetic Acid on Floral Induction and Apical Differentiation in Chenopodium rubrum L.

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Abstract
Indol-3yl acetic acid (10−4M) was applied to the plumules of Chenopodium rubrum. Effects on the anatomical structure and the growth pattern in the apical meristem, as well as DNA synthesis and nucleolus size were investigated. When auxin is applied before or during photoperiodic induction it inhibits DNA synthesis and meristematic activity. The axillary meristem (i.e. a group of cells in the axils of the leaf primordia) is most affected. A similar inhibition of the axillary meristem was also observed in non-induced control plants grown in continuous light. Auxin applied simultaneously with photoperiodic induction counteracts the reduction of apical dominance in the apex and thus inhibits the onset of floral differentiation. Auxin applied following induction inhibits the previously-formed buds and makes possible a more complete development of the apical flower. The dual effect of IAA on flowering, inhibitory and stimulatory, manifests itself as a growth response at different stages of the changing shoot apex.