lower and gain water from a solution of higher Of course, the solution at which the tissue neither gains nor loses water has a y equal to that of the tissue In a living plant cell, when water is lost to the point of zero turgor pressure, the plasmalemma begins to pull away from the wall. The cell is said to be plasmolyzed. Most cells die once plasmolyzed. If tissues are placed in a range of sugar solutions with known u, it should be possible to find the point at which plasmolysis just begins (incipient plasmolysis). The y of this solution, as in all the others, equals the y of the tissue after equilibration; however, at incipient plasmolysis the y of the cell equals its p I because the u p=0 at this point. Thus, the of the external solution is equal to the p I of the cell. you will use onion skin cells to observe plasmolysis Materials needed Onion bulb or dayflower leaves Equipment and chemicals needed Microscope, absorbent paper, slides and cover slips, droppers, forceps, razor blades petri dishes(diameter: 6cm), beakers, reagent bottle, volumetric flask, measuring cylinder, 0.03%neutral red solution, sucrose solutions at different concentrations(0.30. 0.35 0.40、0.45、0.50、0.55、060、0.65、0.70mol·kg-1) Procedure 1. Mark 9 sets of petri dishes; put one of the above sucrose solutions into each petri dish to form a thin layer. Cover each petri dish with a lid for later use 2. From the onion, cut 0.5 cm2 pieces and remove small strips of the skin Rapidly place 4-5 strips in each of the following sucrose solutions: (0.30.0.350.400.450.50 0.55、0.60、0.65、0.70mol·kg-1). Record the room temperature.( For better observation, Idly dip the onion skin strips into 0.03%neutral red solution, blot dry with paper towels before placing them in sucrose solutions) 3. After 5-10 minutes, place a drop of each of the above sucrose solutions onto different slides. take a strip from each sucrose solution and place it in the sucrose drop with the same concentration, cover the slides with cover slips 4. Observe the onion skin cells for plasmolysis and record the concentration of the
lower Ψ and gain water from a solution of higher Ψ. Of course, the solution at which the tissue neither gains nor loses water has a Ψ equal to that of the tissue. In a living plant cell, when water is lost to the point of zero turgor pressure, the plasmalemma begins to pull away from the wall. The cell is said to be plasmolyzed. Most cells die once plasmolyzed. If tissues are placed in a range of sugar solutions with known Ψ, it should be possible to find the point at which plasmolysis just begins (incipient plasmolysis). The Ψ of this solution, as in all the others, equals the Ψ of the tissue after equilibration; however, at incipient plasmolysis the Ψ of the cell equals its Ψπ because the Ψp = 0 at this point. Thus, theΨ of the external solution is equal to the Ψπ of the cell. you will use onion skin cells to observe plasmolysis. Materials needed Onion bulb or dayflower leaves. Equipment and chemicals needed Microscope, absorbent paper,slides and cover slips,droppers,forceps,razor blades, petri dishes (diameter: 6cm),beakers,reagent bottle, volumetric flask,measuring cylinder, 0.03％neutral red solution,sucrose solutions at different concentrations (0.30 、0.35、 0.40、0.45、0.50、0.55、0.60、0.65、0.70 mol·kg-1). Procedure 1. Mark 9 sets of petri dishes; put one of the above sucrose solutions into each petri dish to form a thin layer. Cover each petri dish with a lid for later use. 2.From the onion, cut 0.5 cm2 pieces and remove small strips of the skinRapidly place 4-5 strips in each of the following sucrose solutions: (0.30 、0.35、0.40、0.45、0.50、 0.55、0.60、0.65、0.70 mol·kg-1). Record the room temperature. (For better observation, rapidly dip the onion skin strips into 0.03％neutral red solution, blot dry with paper towels before placing them in sucrose solutions). 3. After 5-10 minutes, place a drop of each of the above sucrose solutions onto different slides.take a strip from each sucrose solution and place it in the sucrose drop with the same concentration, coverthe slides with cover slips. 4. Observe the onion skin cells for plasmolysis and record the concentration of the 16
appropriate solution. Determine which solution indicates the osmotic potential of the onion tissue 5. Record your results in table 1.1 Table 1.1 Measuring Osmetic Potential of Onion Tissue Student name Date Material used Room temperature Concentrations of Relative extent of plasmolysis Percentage of cells that has sucrose solution(%) ( Do the graph representation plasmolyzed(%) 6. Using the information obtained and the following formula, calculate the osmetic pressure of the leaf tissue.pr=-CRTi×1.013×0.1。中= osmetic potential of cooresponding sucrose solution, C=concentration of cooresponding sucrose solution mol/L).R=Gas constant (0.008314MPa/L/mol/k). T= Absolute temperature i lonization coefficient( sucrose=1), 1 atmosphere standard =1.013=0.1MPa 6. Discussion 1. What are the components of water potential of plant tissues at the moment when plasmolysis takes place? 2. Under what circumstances that plasmolysis will take place? What measures can be taken for deplasmolysis to take place?
appropriate solution. Determine which solution indicates the osmotic potential of the onion tissue. 5. Record your results in table1.1. Table 1.1 Measuring Osmetic Potential of Onion Tissue Student name_________ Date__________Material used__________Room temperature Concentrations of Relative extent of plasmolysis Percentage of cells that has sucrose solution(%) (Do the graph representation) plasmolyzed (%) 6. Using the information obtained and the following formula, calculate the osmetic pressure of the leaf tissue.ψπ＝－CRTi×1.013×0.1。ψπ＝osmetic potential of cooresponding sucrose solution，C＝concentration of cooresponding sucrose solution （mol/L），R＝Gas constant（0.008314MPa/L/mol/K），T＝Absolute temperature，i ＝Ionization coefficient（sucrose＝1），1 atmosphere standard＝1.013＝0.1MPa。 6. Discussion 1. What are the components of water potential of plant tissues at the moment when plasmolysis takes place? 2. Under what circumstances that plasmolysis will take place? What measures can be taken for deplasmolysis to take place? 17
实验2植物组织水势的测定(小液流法) 【实验目的】 进一步了解植物水势的概念·掌握植物组织水势的测定方法 【实验原理】 捋植物组织分别放在一系列浓度递增的溶液中·当某一浓度的溶液与植物组织 之间水分保持动态平衡时·则可认为此植物组织的水势等于该溶液的水势。因溶液 浓度是已知的·可以根据公式算出其渗透压·取其负值即为溶液的渗透势(中n) 代表的是植物水势(中w)( waterpotential)值.计算公式如下: P=-iCRT(大气压) (公式1) 【实验材料】 小白菜或其它作物叶片。 【设备与试剂】 带塞青霉素小瓶12个·带有橡皮管的注射针头·镊子·打孔器·培养皿·蔗糖 溶液【0.050.10·0.150.200.250.30mol·L-1】;甲烯蓝粉末 【实验步骤】 1.配制溶液 取干燥洁净的青霉素瓶6个为甲组·各瓶中分别加入0.05~0.30mo·L-1蔗糖溶 液约4m(约为青霉素瓶的2/3处)·另取6个干燥洁净的青霉素瓶为乙组·各瓶 中分别加入0.05~0.3omo-L-1蔗糖溶液1m和微量甲烯蓝粉末着色·上述各瓶加标 签注明浓度。 2.取材 取待测样品的功能叶数片·用打孔器打取小圆片约50片·放至培养皿中·混 均勻。用镊子分别夹入5~8个小圆片到盛有不同浓度的甲烯蓝蔗糖溶液的试剂瓶中 (乙组)°盖上瓶塞·并使叶圆片全部浸没于溶液中。放置约30~60min:为加速 水分平衡·应经常摇动小瓶。 3.观察
实验2 植物组织水势的测定（小液流法） 【实验目的】 进一步了解植物水势的概念，掌握植物组织水势的测定方法。 【实验原理】 将植物组织分别放在一系列浓度递增的溶液中，当某一浓度的溶液与植物组织 之间水分保持动态平衡时，则可认为此植物组织的水势等于该溶液的水势。因溶液 浓度是已知的，可以根据公式算出其渗透压，取其负值即为溶液的渗透势（ψ ）， 代表的是植物水势（ψ ψ ＝－P＝－iCRT（大气压） （公式1） 【实验材料】 小白菜或其它作物叶片。 【设备与试剂】 带塞青霉素小瓶12 个，带有橡皮管的注射针头，镊子，打孔器，培养皿，蔗糖 溶液【0.05、0.10、0.15、0.20、0.25、0.30mol·L-1】；甲烯蓝粉末。 【实验步骤】 1. 配制溶液 取干燥洁净的青霉素瓶6 个为甲组，各瓶中分别加入0.05～0.30mol•L-1 蔗糖溶 液约4ml（约为青霉素瓶的2／3 处），另取6 个干燥洁净的青霉素瓶为乙组，各瓶 中分别加入0.05～0.30mol•L-1 蔗糖溶液1ml 和微量甲烯蓝粉末着色，上述各瓶加标 签注明浓度。 2. 取材 取待测样品的功能叶数片，用打孔器打取小圆片约50 片，放至培养皿中，混合 均匀。用镊子分别夹入5～8个小圆片到盛有不同浓度的甲烯蓝蔗糖溶液的试剂瓶中 （乙组）。盖上瓶塞，并使叶圆片全部浸没于溶液中。放置约30～60min，为加速 水分平衡，应经常摇动小瓶。 3. 观察 π w）（waterpotential）值。计算公式如下： w＝ψ π
经一定时间后·用注射针头吸取乙组各瓶蓝色糖液少许·将针头插入对应浓度 甲组青霉素瓶溶液中部·小∽心地放出少量液流·观察蓝色液流的升降动向。(每 测定均要用待测浓度的甲烯蓝蔗糖溶液清洗几交注射针头)。若液流上升·说明浸 过小圆片的蔗糖溶液浓度变小(即植物组织失水);表明叶片组织的水势高于该浓 度糖溶液的渗透势;如果蓝色液流下降则说明叶片组织的水势低于该糖溶液的渗透 势·若蓝色液流静止不动·则说明叶片组织的水势等于该糖溶液的渗透势·此糖溶 液的浓度即为叶片组织的等渗浓度 4.结果计算 将求得的等渗浓度值代入公式:ψw=n=-CRT×1.013×0.1(公式2) 式中:中w=植物组织的水势(单位:Mpa)申 =溶液的渗透势·C=等渗浓 度(mo-1)·R=气体常数(0008314MPa/Lmo/K)·T=绝对温度·i=解离系 数(蔗糖=1·CaC2=260)·1大气压=1.013×105Pa=0.1MPa 【讨论】 1、水分运动的驱动力是什么?是如何产生的? 2、水分运动时主动的还是被动的?能忽略中吗?为什么?
经一定时间后，用注射针头吸取乙组各瓶蓝色糖液少许，将针头插入对应浓度 甲组青霉素瓶溶液中部，小心地放出少量液流，观察蓝色液流的升降动向。（每次 测定均要用待测浓度的甲烯蓝蔗糖溶液清洗几次注射针头）。若液流上升，说明浸 过小圆片的蔗糖溶液浓度变小（即植物组织失水）；表明叶片组织的水势高于该浓 度糖溶液的渗透势；如果蓝色液流下降则说明叶片组织的水势低于该糖溶液的渗透 势，若蓝色液流静止不动，则说明叶片组织的水势等于该糖溶液的渗透势，此糖溶 液的浓度即为叶片组织的等渗浓度。 4. 结果计算 将求得的等渗浓度值代入公式：ψ ＝－CRTi×1.013×0.1 （公式2） 式中：ψ ＝溶液的渗透势，C＝等渗浓 度（mol•L-1），R＝气体常数（0.008314MPa/L/mol/K），T＝绝对温度，i＝解离系 数（蔗糖＝1，CaCl2＝2.60），1 大气压＝1.013×105Pa＝0.1MPa。 【讨论】： 1、水分运动的驱动力是什么？是如何产生的？ 2、水分运动时主动的还是被动的？能忽略ψ 19 w＝ψ w＝植物组织的水势（单位：Mpa）ψ P吗？为什么？ π π
Experiment 2 easuring Water Potential of Plant Tissues by Small Fluid-flow Method To understand the concept and value of water potential To examine the various components of water potential Introduction Water flows from regions of high water potential to regions of low water potential.A tissue's water potential can be inferred by immersing samples of that tissue in a range of solutions having known water potentials. Uptake or loss of water means that a gradient in water potential exists between the tissue and the bathing solution. No net water uptake indicates that the tissue and its surrounding solution have the same water potential (they are in"equilibrium"). In this exercise, you will determine the water potential of plant leaves by immersing leaf samples in sucrose solutions of varying concentrations. If the leaf tissue has a lower water potential than that of the solution, water flows from the solution into the leaf tissue, concentrating the sucrose solution. Otherwise water flows from the leaf into the solution, diluting the sucrose solution, if the leaf tissue has the same water potential, the net movement of water between the solution and the tissue would be zero, no change in sucrose concentration By measuring the change in concentration of he sucrose solutions, it is possible to calculate the osmotic potential of the solution without concentration change: for which signifies that the solution and the tissue have the same water potential Materials needed Leaves of lettuce or other plants Equipment and chemicals needed 12 reagent bottles, injection needles, petri dishes, forceps, hole-punch, I mol.L-1 sucrose solution(22 liters), methylene blue powder Procedures(Students work in teams of 2) 1. Froma l mol L-1 sucrose solution, prepare 10 ml quantities of each of the following sucrose solutions:0.05、0.10、0.15、0.20、0.25、0.30molL-1
Experiment 2 Measuring Water Potential of Plant Tissues by Small Fluid-flow Method Goals To understand the concept and value of water potential.To examine thevarious components of water potential. Introduction Water flows from regions of high water potential to regions of low water potential. A tissue's water potential can be inferred by immersing samples of that tissue in a range of solutions having known water potentials. Uptake or loss of water means that a gradient in water potential exists between the tissue and the bathing solution. No net water uptake indicates that the tissue and its surrounding solution have the same water potential (they are in "equilibrium"). In this exercise, you will determine the water potential of plant leaves by immersing leaf samples in sucrose solutions of varying concentrations. If the leaf tissue has a lower water potential than that of the solution, water flows from the solution into the leaf tissue, concentrating the sucrose solution. Otherwise water flows from the leaf into the solution, diluting the sucrose solution, if the leaf tissue has the same water potential, the net movement of water between the solution and the tissue would be zero, no change in sucrose concentration. By measuring the change in concentration of the sucrose solutions, it is possible to calculate the osmotic potential of the solution without concentration change; for which signifies that the solutionand the tissue have the same water potential. Materials needed Leaves of lettuce or other plants. Equipment and chemicals needed 12 reagent bottles, injection needles, petri dishes, forceps, hole-punch, 1 mol·L-1 sucrose solution (≥2 liters) , methylene blue powder. Procedures (Students work in teams of 2) 1. Froma 1 mol·L-1 sucrose solution, prepare 10 ml quantities of each of the following sucrose solutions: 0.05、0.10、0.15、0.20、0.25、0.30mol•L-1 20