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