植物对内在与外在讯息的反应

1、Copyright 2005 Pearson Education, Inc. publishing as Benjamin CummingsPowerPoint Lectures for Biology, Seventh EditionNeil Campbell and Jane ReeceLectures by Chris Romero(6) Chapter 39Plant Responses to Internal and External Signals植物對內在與外在訊息的反應植物對內在與外在訊息的反應Copyright 2005 Pearson Education, Inc. pub

2、lishing as Benjamin Cummings Concept 39.1: Signal transduction pathways link signal reception to response Concept 39.2: Plant hormones help coordinate growth, development, and responses to stimuli Concept 39.3: Responses to light are critical for plant success Concept 39.4: Plants respond to a wide

3、variety of stimuli other than light Concept 39.5: Plants defend themselves against herbivores and pathogensKey ConceptsCopyright 2005 Pearson Education, Inc. publishing as Benjamin CummingsStimulus and response (刺激與回應刺激與回應)Overview: Stimuli and a Stationary Life (刺激與穩定刺激與穩定)Plants, being rooted to t

4、he ground must respond to whatever environmental change (環境變遷環境變遷) comes their wayFor example, the bending of a grass seedling (幼苗幼苗的彎曲的彎曲) toward light begins with the plant sensing the direction, quantity, and color of the lightFigure 39.1Copyright 2005 Pearson Education, Inc. publishing as Benjam

5、in Cummings Concept 39.1: Signal transduction pathways link signal reception to response Plants have cellular receptors (細胞接受器細胞接受器) That they use to detect important changes in their environment For a stimulus to elicit a response (為了誘發為了誘發對一個刺激的回應對一個刺激的回應) Certain cells must have an appropriate re

6、ceptorStimulus and response (刺激與回應刺激與回應)Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings A potato left growing in darkness (馬鈴薯在馬鈴薯在黑暗中的生長黑暗中的生長) will produce shoots that do not appear healthy, and will lack elongated roots These are morphological adaptations (形態形態適應適應) for gro

7、wing in darkness collectively referred to as etiolation (白化作用白化作用)Figure 39.2a(a) Before exposure to light. A dark-grown potato has tall, spindly stems and nonexpanded leavesmorphological adaptations that enable the shoots to penetrate the soil. The roots are short, but there is little need for wate

8、r absorption because little water is lost by the shoots.Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings After the potato is exposed to lightThe plant undergoes profound changes called de-etiolation (去白化作用去白化作用), in which shoots and roots grow normallyFigure 39.2b (b) After a w

9、eeks exposure to natural daylight. The potato plant begins to resemble a typical plant with broad green leaves, short sturdy stems, and long roots. This transformation begins with the reception of light by a specific pigment, phytochrome (光敏素光敏素).Copyright 2005 Pearson Education, Inc. publishing as

10、Benjamin Cummings The potatos response to light is an example of cell-signal processing (細胞細胞- -訊訊息加工過程息加工過程)Figure 39.3Cell wallCytoplasmReceptorRelay moleculesActivationof cellularresponsesHormone orenvironmentalstimulusPlasma membrane1. Reception2. Transduction3. Response1. 接收接收2. 傳遞傳遞3. 反應反應細胞反應

11、細胞反應的活化的活化賀爾蒙或賀爾蒙或環境刺激環境刺激受體受體(接受器接受器)備用分子備用分子(第二傳訊者第二傳訊者)Copyright 2005 Pearson Education, Inc. publishing as Benjamin CummingsReception (接收或接受接收或接受) Internal and external signals are detected by receptors (接受器偵測內在與外在訊息接受器偵測內在與外在訊息) Proteins that change in response to specific stimuli Reception pro

12、tein (受體蛋白受體蛋白)Copyright 2005 Pearson Education, Inc. publishing as Benjamin CummingsTransduction (傳遞傳遞/傳導傳導) Second messengers (第二傳訊者第二傳訊者) Transfer and amplify signals (轉移與擴大訊轉移與擴大訊息息) from receptors to proteins that cause specific responsesCopyright 2005 Pearson Education, Inc. publishing as Benj

13、amin CummingsFigure 39.4Plant signal transduction (植物的訊息傳遞植物的訊息傳遞)An example of signal transduction in plantsTranscription 1 Reception 2 Transduction 3 ResponseCYTOPLASMPlasmamembranePhytochromeactivatedby lightCellwallLightcGMPSecond messengerproducedSpecificproteinkinase 1activatedTranscriptionfac

14、tor 1PPTranslationDe-etiolation(greening)responseproteinsCa2+Ca2+ channelopenedSpecificproteinkinase 2activatedTranscriptionfactor 21 The light signal isdetected by thephytochrome receptor,which then activatesat least two signaltransduction pathways.2 One pathway uses cGMP as a second messenger that

15、 activates a specific protein kinase.The other pathway involves an increase incytoplasmic Ca2+ that activates another specific protein kinase.3 Both pathwayslead to expressionof genes for proteinsthat function in thede-etiolation(greening) response.NUCLEUSCopyright 2005 Pearson Education, Inc. publi

16、shing as Benjamin CummingsResponse (回應或反應回應或反應) Ultimately, a signal transduction pathway Leads to a regulation of one or more cellular activities In most cases These responses to stimulation involve the increased activity of certain enzymes Protein kinasesCopyright 2005 Pearson Education, Inc. publ

17、ishing as Benjamin CummingsTranscriptional Regulation (轉錄調節轉錄調節) Transcription factors bind directly to specific regions of DNA And control the transcription of specific genesCopyright 2005 Pearson Education, Inc. publishing as Benjamin CummingsPost-Translational Modification of Proteins Post-transl

18、ational modification (轉譯後修飾轉譯後修飾) Involves the activation of existing proteins involved in the signal response真核細胞真核細胞細胞核細胞核蛋白質蛋白質核醣體核醣體轉譯轉譯轉錄轉錄RNA加工加工Post-transcription modificationPost-translation modificationCopyright 2005 Pearson Education, Inc. publishing as Benjamin CummingsDe-Etioloation (“Gr

19、eening”) Proteins去白化去白化( (綠化綠化) )蛋白蛋白 Many enzymes that function in certain signal responses are involved in photosynthesis directly While others are involved in supplying the chemical precursors (化學前驅物化學前驅物) necessary for chlorophyll productionCopyright 2005 Pearson Education, Inc. publishing as Be

20、njamin Cummings報告完畢報告完畢敬請指教敬請指教！？！？！？！？！？！？！？！？！？！？！？！？Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings Concept 39.2: Plant hormones help coordinate growth, development, and responses to stimuli Hormones Are chemical signals (化學訊息化學訊息) that coordinate the different parts of an

21、organism Classification of plant hormonesAuxin, Cytokinins, Gibberellins, Abscisic acids, Ethylene, BrassinosteroidsCopyright 2005 Pearson Education, Inc. publishing as Benjamin CummingsThe Discovery of Plant Hormones Any growth response That results in curvatures of whole plant organs toward or awa

22、y from a stimulus is called a tropism (向性向性) Is often caused by hormones Charles Darwin and his son Francis Conducted some of the earliest experiments on phototropism (向光性向光性), a plants response to light, in the late 19th centuryCopyright 2005 Pearson Education, Inc. publishing as Benjamin CummingsP

23、hoto-signal is a light-activated mobile chemicalFigure 39.5Eperiment: In 1880, Charles Darwin and his son Francis designed an experiment to determine what part of the coleoptile(芽鞘芽鞘) senses light. In 1913, Peter Boysen-Jensen conducted an experiment to determine how the signal for phototropism is t

24、ransmitted. Results:Conclusion: In the Darwins experiment, a phototropic response occurred only when light could reach the tip of coleoptile. Therefore, they concluded that only the tip senses light. Boysen-Jensen observed that a phototropic response occurred if the tip was separated by a permeable

25、barrier (gelatin) but not if separated by an impermeable solid barrier (a mineral called mica). These results suggested that the signal is a light-activated mobile chemical.ControlDarwin and Darwin (1880)Boysen-Jensen (1913)LightShadedside ofcoleoptileIlluminatedside ofcoleoptileLightTipremovedTip c

26、overedby opaquecapTipcoveredby trans-parentcapBase coveredby opaqueshieldLightTip separatedby gelatinblockTip separatedby mica芽鞘照光面芽鞘照光面芽鞘背光面芽鞘背光面雲母雲母Copyright 2005 Pearson Education, Inc. publishing as Benjamin CummingsThe discovery of Auxin (植物生長素植物生長素)In 1926, Frits Went extracted the chemical me

27、ssenger for phototropism, auxin, by modifying earlier experimentsExcised tip placedon agar blockGrowth-promotingchemical diffusesinto agar blockAgar blockwith chemicalstimulates growthControl(agar blocklackingchemical)has noeffectControlOffset blockscause curvatureFigure 39.6Experiment: In 1926, Fri

28、ts Wents experiment identified how a growth-promoting chemical causes a coleoptile to grow toward light. He placed coleoptiles in the dark and removed their tips, putting some tips on agar blocks that he predicted would absorb the chemical. On a control coleoptile, he placed a block that lacked the

29、chemical. On others, he placed blocks containing the chemical, either centered on top of the coleoptile to distribute the chemical evenly or offset to increase the concentration on one side.Results: The coleoptile grew straight if the chemical was distributed evenly. If the chemical was distributed

30、unevenly, the coleoptile curved away from the side with the block, as if growing toward light, even though it was grown in the dark.Conclusion: Went concluded that a coleoptile curved toward light because its dark side had a higher concentration of the growth-promoting chemical, which he named auxin

31、.Copyright 2005 Pearson Education, Inc. publishing as Benjamin CummingsA Survey of Plant HormonesCopyright 2005 Pearson Education, Inc. publishing as Benjamin CummingsA Survey of Plant HormonesCopyright 2005 Pearson Education, Inc. publishing as Benjamin CummingsA Survey of Plant Hormones (1)Copyrig

32、ht 2005 Pearson Education, Inc. publishing as Benjamin CummingsA Survey of Plant Hormones (2)Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings In general, hormones control plant growth and development By affecting the division, elongation, and differentiation of cells Plant horm

33、ones are produced in very low concentrations But a minute amount can have a profound effect on the growth and development of a plant organCopyright 2005 Pearson Education, Inc. publishing as Benjamin CummingsAuxin (植物生長素植物生長素) The term auxin Is used for any chemical substance that promotes cell elon

34、gation (細胞延伸細胞延伸) in different target tissues Auxin transporters (植物生長素運輸蛋白植物生長素運輸蛋白)move the hormone out of the basal end of one cell, and into the apical end of neighboring cellsCopyright 2005 Pearson Education, Inc. publishing as Benjamin CummingsAuxin transporters and polar transport of auxin植物生

35、長素運輸蛋白與其極性運輸植物生長素運輸蛋白與其極性運輸Figure 39.7Cell 1Cell 2100 mEpidermisCortexPhloemXylemPithBasal endof cell25 mExperimrnt: To investigate how auxin is transported unidirectionally, researchers designed an experiment to identify the location of the auxin transport protein. They used a greenish-yellow fluor

36、escent molecule to label antibodies that bind to the auxin transport protein. They applied the antibodies to longitudinally sectioned Arabidopsis stems.Results: The left micrograph shows that the auxin transport protein is not found in all tissues of the stem, but only in the xylem parenchyma. In th

37、e right micrograph, a higher magnification reveals that the auxin transport protein is primarily localized to the basal end of the cells.Conclusion: The results support the hypothesis that concentration of the auxintransport protein at the basal ends of cells is responsible for polar transport of au

38、xin.Copyright 2005 Pearson Education, Inc. publishing as Benjamin CummingsThe Role of Auxin in Cell Elongation According to a model called the acid growth hypothesis Proton pumps play a major role in the growth response of cells to auxinCopyright 2005 Pearson Education, Inc. publishing as Benjamin C

39、ummingsExpansin胞壁擴張酶胞壁擴張酶Cell wallCell wallenzymesCross-linkingcell wallpolysaccharidesMicrofibrilH+H+H+H+H+H+H+H+H+ATPPlasma membranePlasmamembraneCellwallNucleusVacuoleCytoplasmH2OCytoplasm Cell elongation in response to auxinFigure 39.8 1 Auxin increases the activity ofproton pumps.4 The enzymati

40、c cleavingof the cross-linkingpolysaccharides allows the microfibrils to slide (滑動滑動). The extensibility (延展性延展性) of the cell wall is increased. Turgor (膨壓膨壓) causes the cell to expand. 2 The cell wallbecomes moreacidic.5 With the cellulose loosened,the cell can elongate. 3 Wedge-shaped expansins, a

41、ctivated by low pH, separate cellulose microfibrils from cross-linking polysaccharides. The exposed cross-linking polysaccharides are now more accessible to cell wall enzymes.Copyright 2005 Pearson Education, Inc. publishing as Benjamin CummingsPhysiologic functions of auxin in plant Auxin and Cell

42、Elongation : according to a model called the acid growth hypothesis, proton pumps play a major role in the growth response of cells to auxin Lateral and Adventitious Root Formation: Auxin is involved in the formation and branching of roots Auxins as Herbicides: an overdose of auxins can kill eudicot

43、s Other Effects of Auxin: Auxin affects secondary growth by inducing cell division in the vascular cambium and influencing differentiation of secondary xylem Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings報告完畢報告完畢敬請指教敬請指教！？！？！？！？！？！？！？！？！？！？！？！？Copyright 2005 Pearson Education

44、, Inc. publishing as Benjamin CummingsCytokinins (細胞分裂素細胞分裂素) Cytokinins Stimulate cell division Control of Cell Division and Differentiation Cytokinins are produced in actively growing tissues such as roots, embryos, and fruits Work together with auxinCopyright 2005 Pearson Education, Inc. publishi

45、ng as Benjamin CummingsControl of Apical Dominance (頂端優勢頂端優勢)Cytokinins, auxin, and other factors interact in the control of apical dominance. The ability of a terminal bud to suppress development of axillary buds (腋芽腋芽)If the terminal bud (頂芽頂芽) is removed, plants become bushier (茂密茂密)Figure 39.9Ax

46、illary buds“Stump” afterremoval ofapical budLateral branchesCopyright 2005 Pearson Education, Inc. publishing as Benjamin CummingsAnti-Aging Effects (抗老化效應抗老化效應) Cytokinins retard (阻礙阻礙/ /延遲延遲) the aging of some plant organs By inhibiting protein breakdown, stimulating RNA and protein synthesis, and

47、 mobilizing nutrients from surrounding tissuesCopyright 2005 Pearson Education, Inc. publishing as Benjamin CummingsGibberellins (吉貝林素吉貝林素) Gibberellins have a variety of effects such as: stem elongation fruit growth seed germinationCopyright 2005 Pearson Education, Inc. publishing as Benjamin Cummi

48、ngsStem Elongation (莖的延伸莖的延伸) Gibberellins stimulate growth of both leaves and stems In stems Gibberellins stimulate cell elongation and cell divisionCopyright 2005 Pearson Education, Inc. publishing as Benjamin CummingsFruit Growth In many plants Both auxin and gibberellins must be present for frui

49、t to setCopyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings Gibberellins are used commercially In the spraying of Thompson seedless grapesFigure 39.10 Copyright 2005 Pearson Education, Inc. publishing as Benjamin CummingsAfter water is imbibed, the release of gibberellins from the

50、 embryo signals the seeds to break dormancy and germinate (打破休眠促進萌芽打破休眠促進萌芽)Germinationbreak seed dorminancy to germinateFigure 39.112. The aleurone responds by synthesizing and secreting digestive enzymes thathydrolyze stored nutrients inthe endosperm. One exampleis -amylase, which hydrolyzesstarch

51、. (A similar enzyme inour saliva helps in digestingbread and other starchy foods.)Aleurone糊粉層糊粉層Endosperm內胚乳內胚乳WaterScutellum(cotyledon)子葉子葉GAGA -amylaseRadicle胚根胚根Sugar1. After a seed imbibes water, the embryo releasesgibberellin (GA) as a signal to the aleurone, the thin outer layer of the endospe

52、rm.3. Sugars and other nutrients absorbed from the endosperm by the scutellum (cotyledon) are consumed during growth of the embryo into a seedling.澱粉澱粉分解酶分解酶seedlingshootrootCopyright 2005 Pearson Education, Inc. publishing as Benjamin CummingsBrassinosteroids (油菜類固醇油菜類固醇) Brassinosteroids Are simil

53、ar to the sex hormones of animals Induce cell elongation and divisionCopyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings報告完畢報告完畢敬請指教敬請指教！？！？！？！？！？！？！？！？！？！？！？！？Copyright 2005 Pearson Education, Inc. publishing as Benjamin CummingsAbscisic Acid (離層酸離層酸) Two of the many effects of a

54、bscisic acid (ABA) are Seed dormancy (種子休眠種子休眠) Drought tolerance (耐乾旱耐乾旱)Copyright 2005 Pearson Education, Inc. publishing as Benjamin CummingsSeed Dormancy (種子休眠種子休眠) Seed dormancy has great survival value Because it ensures that the seed will germinate only when there are optimal conditionsCopyri

55、ght 2005 Pearson Education, Inc. publishing as Benjamin CummingsPrecocious germination (早熟的萌芽早熟的萌芽) is observed in maize mutantsThat lack a functional transcription factor (功能性功能性轉錄因子轉錄因子) required for ABA to induce expression of certain genesFigure 39.12Coleoptile芽鞘芽鞘Copyright 2005 Pearson Educatio

56、n, Inc. publishing as Benjamin CummingsDrought Tolerance (耐乾旱耐乾旱) ABA is the primary internal signal That enables plants to withstand droughtCopyright 2005 Pearson Education, Inc. publishing as Benjamin CummingsEthylene (乙烯乙烯) Plants produce ethylene in response to stresses (逆境逆境) such as Drought (乾

57、旱乾旱) flooding (淹水淹水) mechanical pressure (機械性壓破機械性壓破) injury (受傷受傷) Infection (感染感染)Copyright 2005 Pearson Education, Inc. publishing as Benjamin CummingsThe Triple Response to Mechanical StressEthylene induces the triple response (三重反應三重反應) which allows a growing shoot to avoid obstacles (障礙障礙)Figu

58、re 39.13Conclusion: Ethylene induces the triple response in pea seedlings, with increased ethylene concentration causing increased response.Experiment: Germinating pea seedlings were placed in the dark and exposed to varying ethylene concentrations. Their growth was compared with a control seedling

59、not treated with ethylene.Results: All the treated seedlings exhibited the triple response. Response was greater with increased concentration.0.000.100.200.400.80Ethylene concentration (parts per million, ppm)Triple response to avoid obstacles1. A slowing of stem elongation2. A thickening of the ste

60、m which makes it strong3. A curvature that causes the stem to start growing horizonically Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings Ethylene-insensitive mutants Fail to undergo the triple response after exposure to ethyleneFigure 39.14aein mutantCopyright 2005 Pearson Ed