Morphactin stimulates stem elongation and thickening in decapitated shoots of Bryophyllum calycinum Salisb.

Abstract

Morphactin, methyl 2-chloro-9-hydroxyfluorene-9-carboxylate (IT 3456), is a synthetic growth regulator with a unique action affecting various morphogenetic and physiological processes in plants, and has been characterized as a specific inhibitor of auxin polar transport. Morphactin applied at the last internode in decapitated shoots of Bryophyllum calycinum substantially stimulated elongation and thickening of the internode. Benzyladenine applied alone little affected stem elongation and thickening. Simultaneous application of benzyladenine and morphactin showed a synergistic effect on thickening, while it did not on elongation. These results suggest that morphactin translocated basipetally from the top of the treated internode inhibits auxin polar transport from the internode, resulting in the accumulation of endogenous auxin for elongation and thickening in the treated internode of decapitated shoots of Bryophyllum calycinum.

Keywords

• Bryophyllum calycinum
• elongation
• internode
• methyl 2-chloro-9-hydroxyfluorene-9-carboxylate
• thickening
• morphactin