《維管植物的運輸》PPT课件

1、Chapter 36,Transport in Vascular Plants 維管植物的運輸,Overview: Pathways for Survival of vascular plant (維管植物存活途徑) For vascular plants, the evolutionary journey (演化之旅) onto land involved the differentiation of the plant body into roots and shoots (植物體分化為根與枝條) Vascular tissue transports nutrients throughou

2、t a plant; such transport may occur over long distances (長途運輸,Figure 36.1,Key Concepts,Concept 36.1: Physical forces drive the transport of materials in plants over a range of distances Concept 36.2: Roots absorb water and minerals from the soil Concept 36.3: Water and minerals ascend from roots to

3、shoots through xylem (木質部) Concept 36.4: Stomata help regulate the rate of transpiration (蒸散作用) Concept 36.5: Organic nutrients are translocated through the phloem (韌皮部,Concept 36.1: Physical forces drive the transport of materials in plants over a range of distances Transport in vascular plants occ

4、urs on three scales (三種尺度/三種層次) Transport of water and solutes by individual cells, such as root hairs (個別細胞水與溶質的運輸) Short-distance transport of substances from cell to cell at the levels of tissues and organs (組織與器官內細胞間物質的短距離運輸) Long-distance transport within xylem and phloem at the level of the wh

5、ole plant (整株植物木質部與韌皮部的長距離運輸,A variety of physical processes (物理過程) are involved in the different types of transport (眾 多物理過程介入或參與不同型式的運輸,Figure 36.2,木質液,木質液,蒸散作用,韌皮液,Selective Permeability of Membranes: A Review膜的選擇通透性-各種膜系統,The selective permeability (選擇通透性) of a plant cells plasma membrane (細胞膜)

6、Controls the movement of solutes into and out of the cell Specific transport proteins/transportor (專一性輸送蛋白) Enable plant cells to maintain an internal environment different from their surroundings Solutes in cell: cation (陽離子), anion (陰離子), neutral solute (中性溶質,The Central Role of Proton Pumps (質子唧筒

7、,Proton pumps (質子唧筒) in plant cells Create a hydrogen ion gradient (氫離子梯度) that is a form of potential energy (潛能) that can be harnessed (=used) to do work (作功) Contribute to a voltage known as a membrane potential (膜電位), also a kind of potential energy,Figure 36.3,細胞質,細胞外液,Plant cells use energy st

8、ored in the proton gradient (氫離子梯度) and membrane potential (膜電位), both of which are potential energy To drive the transport of many different solutes,Figure 36.4a,In the mechanism called cotransport (共同運輸) A transport protein (cotransporter) couples the passage of one solute to the passage of anothe

9、r,Figure 36.4b,H,H,H,H,H,H,H,H,H,H,H,H,NO3,NO3,NO3,NO3,NO3,NO3,NO3,b) Cotransport of anions (陰離子的共同運輸,H,of through a cotransporter,Cell accumulates anions ( , for example) by coupling their transport to theinward diffusion,共同運輸蛋白,高濃度H+ 低濃度NO3,低濃度H+ 高濃度NO3,cotransporter,細胞質,細胞外液,Figure 36.4c,The “coa

10、ttail” effect of cotransport (共同運輸) Is also responsible for the uptake of the sugar sucrose (neutral solute) by plant cells,低濃度H+ 高濃度sugar,高濃度H+ 低濃度sugar,報告完畢 敬請指教,Effects of Differences in Water Potential水勢差的效應,To survive plants must balance water uptake and loss Differences in water potential driv

11、e water transport in plant cells (水勢差驅動植物細胞中的水份運輸) Osmosis (滲透作用) Determines the net uptake or water loss by a cell Is affected by solute concentration and pressure,Osmotic pressure (滲透壓) in animal cells low osmotic pressure=low solute=high water high osmotic pressure=high solute=low water Direction

12、 of moving water low osmotic pressure=low solute=high water high osmotic pressure=high solute=low water Isotonic solution(等張溶液)、 hypertonic solution(高張溶液)、 hypotonic solution(低張溶液,Water potential (水勢) Is a measurement that combines the effects of solute concentration and pressure Determines the dire

13、ction of movement of water Water Flows from regions of high water potential to regions of low water potential Solute (溶質,Water,Solute,In,Out,Membrane,How Solutes and Pressure Affect Water Potential,Both pressure and solute concentration Affect water potential The solute potential of a solution Is pr

14、oportional to the number of dissolved molecules Pressure potential Is the physical pressure on a solution,Quantitative Analysis of Water Potential (水勢,The addition of solutes reduces water potential,Figure 36.5a,High solute =Low water potential Low solute =High water potential,Application of physica

15、l pressure (物理性壓力) Increases water potential (水勢,Figure 36.5b, c,Negative pressure (負壓) Decreases water potential,Figure 36.5d,Water potential (水勢) Affects uptake and loss of water by plant cells If a flaccid cell (鬆弛細胞) is placed in an environment with a higher solute concentration The cell will lo

16、se water and become plasmolyzed (膜壁分離,If the same flaccid cell is placed in a solution with a lower solute concentration The cell will gain water and become turgid (膨脹,Distilled water,Initial flaccid cell,Turgid cell at osmotic equilibrium with its surroundings,P = 0 S = 0.7,P = 0 S = 0,P = 0.7 S =

17、0.7,Figure 36.6b,= 0.7 MPa,= 0 MPa,= 0 MPa,Turgor (膨壓) loss in plants causes wilting (萎凋) Which can be reversed when the plant is watered (澆水,Figure 36.7,報告完畢 敬請指教,Aquaporin Proteins and Water Transport,Aquaporins (水孔蛋白) Are transport proteins (運轉蛋白) in the cell membrane that allow the passage of wa

18、ter Do not affect water potential,Three Major Compartments (區間) of Vacuolated Plant Cells,Transport is also regulated By the compartmental structure of plant cells Compartmentation (區間化/區隔化/間隔化) Cell wall (細胞壁) Cytosol (細胞質液) Vacuole (液胞,The plasma membrane (細胞膜) Directly controls the traffic of mol

19、ecules into and out of the protoplast Is a barrier between two major compartments (區間), the cell wall and the cytosol,Cell compartments (細胞間隔) ：同一細胞內,The third major compartment in most mature plant cells is the vacuole, a large organelle that can occupy as much as 90% of more of the protoplasts vol

20、ume The vacuolar membrane (液胞膜) regulates transport between the cytosol and the vacuole,Figure 36.8a,Transport proteins in the plasma membrane regulate traffic of molecules between the cytosol and the cell wall,Transport proteins in the vacuolar membrane regulate traffic of molecules between the cyt

21、osol and the vacuole,3. Plasmodesma (細胞質連絡絲,1. Vacuolar membrane (tonoplast) (液胞膜,2. Plasma membrane,Cell wall,Cytosol,Vacuole,Three compartments,In most plant tissues The cell walls and cytosol are continuous from cell to cell The cytoplasmic continuum Is called the symplast (共質體/合胞體) The apoplast

22、(離質體/非原質體/質外體) Is the continuum of cell walls plus extracellular spaces,Tissue compartments (組織間隔) ：不同細胞間,Figure 36.8b,Functions of the Symplast and Apoplast in Transport,Water and minerals can travel through a plant by one of three routes Out of one cell, across a cell wall, and into another cell V

23、ia the symplast (共質體/合胞體) Along the apoplast (離質體/非原質體/質外體,Bulk Flow in Long-Distance Transport長距離運輸的巨流,In bulk flow (巨流) Movement of fluid (sap) in the xylem and phloem is driven by pressure differences (壓力差) at opposite ends of the xylem vessels (木質部導管) and phloem sieve tubes (韌皮部篩管,報告完畢 敬請指教,Conc

24、ept 36.2: Roots absorb water and minerals from the soil Water and mineral salts (礦物鹽) from the soil Enter the plant through the epidermis of roots and ultimately flow to the shoot system,Lateral transport (側向運輸) of minerals and water in roots,Figure 36.9,卡氏帶,維管束,導管,The Roles of Root Hairs, Mycorrhiz

25、ae, and Cortical Cells,Much of the absorption of water and minerals occurs near root tips, where the epidermis is permeable to water and where root hairs are located Root hairs account for much of the surface area of roots,Most plants form mutually beneficial relationships (互利共生) with fungi, which f

26、acilitate (促進) the absorption of water and minerals from the soil Roots and fungi form mycorrhizae (菌根), symbiotic structures(共生結構) consisting of plant roots united with fungal hyphae (菌絲,Figure 36.10,2.5 mm,菌根 是真菌與根的共生結合,Once soil solution enters the roots The extensive surface area of cortical cel

27、l membranes enhances uptake of water and selected minerals,The Endodermis: A Selective Sentry (選擇性進入,The endodermis (內皮層) Is the innermost layer (最內層) of cells in the root cortex Surrounds the vascular cylinder and functions as the last checkpoint (最後關卡) for the selective passage of minerals from th

28、e cortex (皮質) into the vascular tissue (維管束組織,Water can cross the cortex (皮層) Via the symplastic (共質體的) or apoplastic route (質外體的路徑) The waxy Casparian strip (卡氏帶) of the endodermal wall (內皮細胞壁) Blocks apoplastic transfer of minerals from the cortex to the vascular cylinder,報告完畢 敬請指教,Concept 36.3: W

29、ater and minerals ascend (升高) from roots to shoots through the xylem Plants lose an enormous amount of water through transpiration, the loss of water vapor from leaves and other aerial parts of the plant The transpired water must be replaced by water transported up from the roots,Factors Affecting t

30、he Ascent of Xylem Sap,Xylem sap (木質部汁液) Rises to heights of more than 100 m in the tallest plants,Pushing Xylem Sap: Root Pressure (根壓,At night, when transpiration is very low Root cells continue pumping mineral ions into the xylem of the vascular cylinder, lowering the water potential Water flows

31、in from the root cortex (根的皮層) Generating root pressure (根壓) in the xylem,Root pressure (根壓) sometimes results in guttation (點泌作用), the exudation (滲出作用) of water droplets (小水滴) on tips of grass blades or the leaf margins (葉緣) of some small, herbaceous eudicots (草本的真雙子葉植物,Figure 36.11,報告完畢 敬請指教,Pulli

32、ng Xylem Sap: The Transpiration-Cohesion-Tension Mechanism (拉升木質液：蒸散作用內聚力-附著力-張力的作用機制,Water is pulled upward by negative pressure (負壓) in the xylem,Transpirational Pull (蒸散作用的拉力,Water vapor in the airspaces of a leaf Diffuses down its water potential gradient and exits the leaf via stomata,Transpira

33、tion produces negative pressure (tension) in the leaf which exerts a pulling force (拉力) on water in the xylem, pulling water into the leaf,Evaporation causes the air-water interface to retreat farther into the cell wall and become more curved as the rate of transpiration increases. As the interface

34、becomes more curved, the water films pressure becomes more negative. This negative pressure, or tension, pulls water from the xylem, where the pressure is greater,Cuticle,Upper epidermis,Mesophyll,Lower epidermis,Cuticle,Water vapor,CO2,O2,Xylem,CO2,O2,Water vapor,Stoma,Evaporation,At first, the wat

35、er vapor lost by transpiration is replaced by evaporation from the water film that coats mesophyll cells,In transpiration, water vapor (shown as blue dots) diffuses from the moist air spaces of the leaf to the drier air outside via stomata,Airspace,Cytoplasm,Cell wall,Vacuole,Evaporation,Water film,

36、Low rate of transpiration,High rate of transpiration,Air-water interface,Cell wall,Airspace,Y = 0.15 MPa,Y = 10.00 MPa,3,1,2,Figure 36.12,Air-space,Cohesion and Adhesion in the Ascent of Xylem Sap (木質液上升時的凝聚力與附著力,The transpirational pull (蒸散作用拉力) on xylem sap Is transmitted (傳導/傳遞) all the way from

37、the leaves to the root tips and even into the soil solution Is facilitated by cohesion and adhesion (凝聚力與附著力,水份在樹木中的上升作用,Ascent of xylem sap (木質液的上升,Xylem sap,Outside air Y = 100.0 MPa,Leaf Y (air spaces)= 7.0 MPa,Leaf Y (cell walls)= 1.0 MPa,Trunk xylem Y= 0.8 MPa,Water potential gradient,Root xyle

38、m Y= 0.6 MPa,Soil Y= 0.3 MPa,Mesophyll cells,Stoma,Water molecule,Atmosphere,Transpiration,Xylem cells,Adhesion,Cell wall,Cohesion, by hydrogen bonding,Water molecule,Root hair,Soil particle,Water,Cohesion and adhesion in the xylem,Water uptake from soil,Figure 36.13,水勢梯度,Xylem Sap Ascent by Bulk Fl

39、ow: A Review,The movement of xylem sap (木質液) against gravity (重力/萬有引力) Is maintained by the transpiration-cohesion-tension mechanism,報告完畢 敬請指教,The central role of stomata,Concept 36.4: Stomata help regulate the rate of transpiration (氣孔協助調控蒸散速率) Leaves generally have broad surface areas and high sur

40、face-to-volume ratios (表面積/體積比,Both of these characteristics Increase photosynthesis Increase water loss through stomata,Effects of Transpiration on Wilting and Leaf Temperature (蒸散作用對萎凋與葉溫的影響,Plants lose a large amount of water by transpiration If the lost water is not replaced by absorption throug

41、h the roots The plant will lose water and wilt,Transpiration also results in evaporative cooling (蒸發冷卻效應) Which can lower the temperature of a leaf and prevent the denaturation of various enzymes involved in photosynthesis and other metabolic processes,Stomata: Major Pathways for Water Loss,About 90

42、% of the water a plant loses Escapes through stomata,Guard cells (保衛細胞,Each stoma is flanked by guard cells which control the diameter of the stoma by changing shape,a) Changes in guard cell shape and stomatal opening and closing (surface view). Guard cells of a typical angiosperm are illustrated in

43、 their turgid (stoma open) and flaccid (stoma closed) states. The pair of guard cells buckle outward (向外彎曲) when turgid. Cellulose microfibrils in the walls resist stretching and compression in the direction parallel to the microfibrils. Thus, the radial orientation of the microfibrils causes the ce

44、lls to increase in length more than width when turgor increases. The two guard cells are attached at their tips, so the increase in length causes buckling,Figure 36.15a,Changes in turgor pressure (膨壓) that open and close stomata Result primarily from the reversible uptake and loss of potassium (K+)

45、ions by the guard cells,Figure 36.15b,Xerophyte Adaptations That Reduce Transpiration旱生植物減少蒸散作用以適應環境,Xerophytes (旱生植物) Are plants adapted to arid climates (乾旱氣候) Have various leaf modifications (葉的變形) that reduce the rate of transpiration,The stomata of xerophytes (旱生植物的氣孔) Are concentrated on the l

46、ower leaf surface (下表皮) Are often located in depressions that shelter the pores from the dry wind,Figure 36.16,Lower epidermal tissue,Trichomes (“hairs”) 細毛,Cuticle,Upper epidermal tissue,Stomata,100 m,下表皮,上表皮,Concept 36.5: Organic nutrients are translocated (轉移/運移) through the phloem Translocation

47、(轉移/運移) Is the transport of organic nutrients in the plant Phloem sap (韌皮液) Is an aqueous solution that is mostly sucrose Travels from a sugar source to a sugar sink,Phloem sap (韌皮液) Is an aqueous solution that is mostly sucrose Travels from a sugar source to a sugar sink A sugar source (糖的源頭) Is a

48、plant organ that is a net producer of sugar, such as mature leaves A sugar sink (糖的儲存區) Is an organ that is a net consumer or store of sugar, such as a tuber or bulb,Movement from Sugar Sources to Sugar Sinks(自糖源頭到糖儲存區的移動,Figure 36.17a,Mesophyll cell (sugar source,Cell walls (apoplast,Plasma membran

49、e,Plasmodesmata,伴細胞 Companion (transfer) cell,Sieve-tube Member (篩管細胞,Mesophyll cell,Phloem parenchyma cell,Bundle- sheath cell (束鞘細胞,a) Sucrose manufactured in mesophyll cells can travel via the symplast (blue arrows) to sieve-tube members. In some species, sucrose exits the symplast (red arrow) ne

50、ar sieve tubes and is actively accumulated from the apoplast by sieve-tube members and their companion cells,Sugar must be loaded into sieve-tube members (篩管細胞) before being exposed to sinks In many plant species, sugar moves by symplastic and apoplastic pathways,細胞質連絡絲,Cytosol (symplast,Figure 36.17b,b) A chemiosmotic