Mitotic Active CDK stimulates mitosis Inactive CDK Inactive CDKCDK ATP INTERPHASE AE Mitotic cyclin(CM) ∠2ATP FIGURE 1.26(A) Diagram of the cell cycle. (B) Diagram of the regulation of the cell cycle by yclin-dependent protein kinase(CDK). During Inactive CDK G, cyclin(Cg) G. cDk is in its inactive form, CDK becomes activated by binding to G, cyclin(CG )and by being phosphorylated (P)at the activation site. The activated CDK CDK-cyclin complex allows the transition to the S phase. At the end of the S phase. the G, cyclin is degraded and the Activation hibitory CDK is dephosphorylated, resulting in an inactive CDK G, cyclin The cell enters G, During G,, the inactive CDK binds to the degradation Active CDK mitotic cyclin(CM), or M cyclin, At the same time. the stimulates DNA CDK-cyclin complex becomes phosphorylated at both its synthesis activation and its inhibitory sites. The CDK-cyclin complex is still inactive because the inhibitory site is phosphory lated. The inactive complex becomes activated when the phosphate is removed from the inhibitory site by a protein phosphatase, The activated CDK then stimulates the transi tion from G, to mitosis. At the end of mitosis, the mitotic cyclin is degraded and the remaining phosphate at the acti Figure 10-2 vation site is removed by the phosphatase, and the cell enters Gi again
Figure 10-2
cellulose Figure 10-5 S° OH OH OH OH cellulose microfibril hydrogen bond OH OH OH Cellulose fibrils In plant cell walls, each cellulose fibril contains several microfibrils. Each microfibril contains many polymers of glucose hydrogen-bonded together, Three such polymers are shown
Figure 10-5
IAA H+ H H ABPT IAA ATP ATP ATP ABP1 Activation hypothesis IAA ATP H Second messengers Rough ER Golgi body NUCLEUS ATP Protein processing Promoter H+-ATPase gen ATP (5 Synthesis mRNA hypothesis ③3 H*-ATPase in vesicle membrane Plasma membrane CELL WALL Activation Expansin FIGURE 19.25 Current models for IAA-induced H* extrusion, In many plants, bo of these mechanisms may operate. Regardless of how H+ pumping is increased A acid-induced wall loosening is thought to be mediated by expansins. Figure 10-6
Figure 10-6
IAA concentration(mg/ml) 0.0 0.005 0.03 0.18 1.08 3. 0.0 目 0.2 A89 FIGURE 21.13 The regulation of growth and organ formation in cultured tobacco callus at different concentrations of auxin and kinetin. At low auxin and high kinetin concentrations (lower left) buds developed. At high auxin and low kinetin concentrations (upper right) roots developed. At intermediate or high concentra tions of both hormones(middle and lower right) undifferentiated callus developed.( Courtesy of Donald Armstrong. Figure 10-7
Figure 10-7
1、大孢子形成 3、胚乳,糊粉层 (单子叶植物) 2、胚柄退化 1、毛状体发育 ② 7、叶衰老 9、过敏反应(抗病) 8、通气组织形成 5、管状分子形成 根冠 Fig.10-8
Fig.10-8
tracking light curving of stem Igure Phototropism. Time-lapse photograph of a buttercup, Ranunculus ficaria, curving toward and tracking a source of light
Figure 10-11-0
Undivided agar block Divided agar block (A)Dark Corn coleopt excised and placed Coleoptile tip on agar completely divided 2587-49bot by thin piece of mica; 1. 2/ no redistribution Curvature angle of auxin observed (degrees) (B)Unilateral light Coleoptile tip partly divided by thin piece of mica: lateral 25.6 No destruction of auxin 8.1/ 15.4/ redistribution of auxin occurs Unilateral light does not cause the Auxin is transported laterally to the photodestruction of auxin on the shaded side in the tip illuminated side FIGURE 19.27 Evidence that the lateral redistribution of auxin is stimulated by uni directional light in corn coleoptiles igure 10-11
Figure 10-11
b Gravitropism. a Negative gravitropism of the stem of a Coleus plant 24 hours after the plant was placed on its side b. Positive gravitropism of a root emerging from a com kernel. c. Sedimentation of statoliths see arrows), which are amyloplasts containing starch granules, is thought to explain how roots perceive gravity Figure 10-12
Figure 10-12
(A)Vertical orientation 1. IAA is synthesized FIGURE 19.33 Proposed model for the in the shoot and redistribution of auxin during gravitron transported to the pism in maize roots. (After Hasenstein root in the stele and Evans 1988) Cortex Elongation sale s zarre IAA (flavonoid synthesis 2. When the root is vertical, the statoliths in the cap settle to the basal ends of the cells. Auxin Root cap transported acropetally in the root IAA via the stele is distributed equally on all sides of the root cap. The lAA is Root cap cell IAA then transported basipetally within (enlarged) the cortex to the elongation zone. where it regulates cell elongation Statoliths (B) Horizontal orientation 6. The decreased auxin concentration on the upper side stimulates IAA Figure 10-14 the upper side to grow. As a result, the root bends down IAA A 5. The high concentration 4. The majority of the 3. In a horizontal root of auxin on the lower auxin in the cap is the statoliths settle to side of the root inhibits then transported the side of the cap growth basipetally in the cells, triggering polar cortex on the lower transport of lAA to the side of the root lower side of the cap
Figure 10-14
Cell wall胞壁 Plasmamembrane 童粉体 细胞膜 Amyloplast aUxin 生长素Q 无活性的钙调素 Cam unactivity C 3 已被激活的钙调素 CaM activated ER 内质网 a 器密器g业 Ca-pump钙泵 长素泵IAA-pump
Fig.10-15
