Biosynthesis and degradation of auxin 1. Biosynthesis by the tryptophan-dependent 吲哚丙酮途径 and tryptophan-independent pathways can lead only to an increase in the concentration of free iaa 吲哚乙醇途径 Tryptophan-dependent Tryptophan-independent biosynthesis biosynthesis 色氨酸途径 吲哚乙晴途径 Free IAA Conjugation bound auxin 2. Conjugation is reversible and can lead to either an increase or a decrease 4. Both transport and compart mentation can cause either an Oxidation increase or a decrease in the Decarboxylation rosolic IAA concentration Com partmentation depending on the direction of in chloroplast 3. Degradation(either by hormone movement nondecarboxylative oxidation or by decarboxylation) leads only to Transportation pathways Phloem transport Polar transport(coleoptile, yong stem, young root) chemiosmotic polar diffusion theory
Biosynthesis and degradation of auxin 吲哚丙酮途径 色氨酸途径 吲哚乙醇途径 吲哚乙晴途径 Transportation pathways Phloem transport Polar transport (coleoptile, yong stem, young root): chemiosmotic polar diffusion theory Bound auxin
Roles of auxin Stimulation: stem elongation, apical dormancy (顶端优势), cell differentiation( vascular ormation维管束的分化 and wound recovery), root elongation Inhibition: shoot branching (侧枝生长), flower abscission(花朵脱落)
Roles of auxin Stimulation: stem elongation, apical dormancy （顶端优势）, cell differentiation (vascular formation 维管束的分化 and wound recovery), root elongation…… Inhibition: shoot branching (侧枝生长）, flower abscission （花朵脱落）……
Selected roles of auxin +IAA Coleoptile bends in Control growth coleoptile stamp be measurer (no added IAA) LI g1081010610510410310 IAA concentration (M) The auxin-regulated stem elongation is determined by the concentration of auxin: general lower than optimum concentration, stimulate, higher than optimum concentration, inhibit
Selected roles of auxin (Increase stem elongation) The auxin-regulated stem elongation is determined by the concentration of auxin: general lower than optimum concentration, stimulate, higher than optimum concentration, inhibit
Selected roles of auxin (Increase root elongation) Auxin and root development on sten cuttings. (Left) Many adventitious roots developed on a honeysuckle (Lonicera fragrantissima) cutting placed in a solution with a high concentration of synthetic auxin. diddle) Fewer roots developed in a lower auxin concentration. (Right) The cutting placed in water (no auxin) served as a control and did not form roots in the same time period. (oe Eakes, Color Advantage/visuals Auxin promote root elongation only at extremely low concentration(10--10-3M), at higher concentrations(10 6)elongation is always inhibited)
Selected roles of auxin (Increase root elongation) Auxin promote root elongation only at extremely low concentration (10-7~10- 13M), at higher concentrations (10- 6 M) elongation is always inhibited)
Selected roles of auxin ( Promote ce∥ differentiation: vascular formation and wound recovery N IAA in lanolin Wound Vasculan 5:anus
Selected roles of auxin (Promote cell differentiation: vascular formation and wound recovery)