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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 o
4、ccurs 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
5、whole 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 mem
6、brane (細胞膜) 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 Proto
7、n Pumps (質子唧筒),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
8、 use energy stored 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 pas
9、sage of another,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NO
10、3-,cotransporter,細胞質,細胞外液,Figure 36.4c,The “coattail” 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
11、balance water uptake and loss Differences in water potential drive 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
12、=high water high osmotic pressure=high solute=low water Direction 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 th
13、e effects of solute concentration and pressure Determines the direction 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 concentrat
14、ion Affect water potential The solute potential of a solution Is proportional 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 wat
15、er potential Low solute =High water potential,Application of physical 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
16、in an environment with a higher solute concentration The cell will lose 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 = 0.7,Figure 36.6b, = 0.7 MPa, = 0 MPa, = 0 MPa,Turgor (膨壓) loss i
