Figure 8-0 charles Darwin. This portrait was made shortly after Darwin returned to England from his voyage around the world.(The Granger Collection, New York)
Figure 8-0
4-dayold Darwin (1880) Lich From c tents or Darwin concloded op 3: that a growth stimulus is produced in the coleoptile ansmitted to the Intact seedling ip of coleoptile Opaque cap growth 2on t cm (curvature) no-p ROOTS Boysen-Jensen (1913) discover ed toys eeasonth T stimnulus passes through gelatin but not thr water-impermeable barriers Mica sheet Mica sheor phototropic and coleoptile curvature no curvature)(curvature) stump Paal(1919) In 1919.A. Paal provided produced in the tip was rip replaced rowth develops coleoptile stump a unilateral light stimulus wont(1926) n 1926. F w Went showed that the acti romoting substance can diffuse into a gelatin block Coleoptile tips Tips discarded: gelatin Each coleoptile bends in on gelatin t up into smaller aced on total darkness: angle ocks n of curvature car coleoptile stump be measured 20 0.050.100.150.200.250.30 Number of coleoptile IAA in gelatin block (mg/L) Figure 8-1 FIGURE 19.1 ummary of early
Figure 8-1
CHE COOH 2-0H Indole- 3-acetic acid 4-Chloroindole-3-acetic acid Indole-3-butyric acid 4+A FIGURE 19.3 Strucure of three natural auxins. Indole-3-acetic acid(IAA)occurs in butyric acid (IBA) Figue 8-2
Figue 8-2
IAA Plasma 1. IAA enters the cell. either membrane passively in the undissociated form(IAAH)or by secondary Permease H active cotransport in the IAA H anionic form(AA") Apex IAAH Cell wall IAAH pH5 cytosol ATP ATP 2. The cell wall is maintained at an acidic pH by the activity H← IAA PH 3. In the cytosol, which has a of the plasma membrane H neutral pH, the anionic form ATPase ATP pH 7 (IAA ) predominates H acue ATP H 4. The anions exit the cell via auxin anion efflux carriers that are concentrated at the basal ends of each cell in the Base IAA longitudinal pathway IAAH FIGURE 19.13 The chemiosmotic model for olar auxin transport. Shown here is one cell Pc Figure 8-5 in a column of auxin-transporting cells AT (From Jacobs and Gilbert 1983
Figure 8-5
(A) (C Indole-3-pyruvic acid pathway Tryptophan(Trp) Trp monooxygenase Trp decarboxylase IAN COOH TAM Indole-3-pyruvic acid (IPA) Indole-3-acetaldoxime IPA Tryptamine (TAM) Bacterial pathway decarboxylase Amine oxidase NHz Indole-3-acetaldehyde(IAld) Indole-3-acetamide(IAM) Indole-3-acetonitrile(IAN) IAld Nitrilase dehydrogenase .IAM hydrolase Indole-3-acetic acid (IAA) FIGURE 19.6 Tryptophan-dependent pathways of IAA biosynthesis in plants and bacteria. The enzymes that are present only in bacteria are marked with an asterisk. (After Bartel 1997. Figure 8-6
Figure 8-6