Light control of leaf abscission in Coleus (Coleus blumei Benth cv. Ball 2719 Red) appears to be regulated by the quantity of endogenous auxin transported from the leaf blade to the abscission zone. Gas chromatographic-mass spectrophotometric analysis indicated that diffusate collected from leaf tissue treated with red light contained significantly higher levels of auxin than dark and far-red light-treated leaf tissue. In addition, diffusate from red light-treated tissue inhibited abscission of leafless petioles while diffusate from far-red light-treated tissue promoted abcission when compared with diffusate from dark-treated tissue. The effect of red light on abscission could be mimicked by IAA, but not by other phytohormones. An auxin transport inhibitor, 2, 3, 5-triiodobenzoic acid (TIBA), applied either as a lanolin ring around the petiole or vacuum infiltrated into tissue, could completely eliminate any red light effect on abscission. The data are consistent with a phytochrome-mediated light regulation of endogenous auxin level in the leaf which then controls abscission.
All Science Journal Classification (ASJC) codes
- Plant Science