DOCSLIB.ORG

Pressure, Turgor Pressure, Water Potential.Pdf

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Pressure, Turgor Pressure, Water Potential.Pdf Under pressure Water movement in plant cells is complicated by the fact that plant cells may also be under pressure. As plant cells fill up their central vacuoles with water, their plasma membranes push against the walls around the cells. The pressure on plant cells that results from the uptake of water is called turgor pressure. Under pressure As water flows into a plant cell and the cell becomes increasingly firm, or turgid, the increase in turgor pressure may slow the movement of water even if the water concentration hasn’t yet reached equilibrium. Under pressure To understand the relationship between osmosis and turgor pressure, think of a plant cell as a water balloon inside a shoe box. In this case, the latex of the balloon represents the plasma membrane of the cell, and the box is the cell wall. The water balloon is filled with salty water to represent the cytoplasm of the cell. If you attach a hose to the water balloon so that pure water comes into contact with the cytoplasm, then water will flow into the balloon. Under pressure The water is moving by osmosis from an area of low solutes (pure water) to an area of high solutes (the salty solution inside the balloon). As water moves into the balloon, however, the balloon stretches and begins to push against the box. Eventually, the pressure from the box will prevent any more water from flowing into the balloon, even if the solution inside the balloon hasn’t reached equilibrium with the solution from the hose. Under pressure Whether or not water moves in or out of plant cells depends upon both turgor pressure and solute concentration. Botanists combine both of these factors to determine water potential of a cell. Water potential is represented by the symbol and is measured in megapascals (mPa), which is a unit of pressure (one atmosphere, which is the pressure that the atmosphere puts on the earth at sea level, equals 0.1 mPa). Under pressure You can think of water potential as the tendency of water to leave one place in favor of another. To figure out the water potential of a cell or solution within a plant, you add together the effects of solute concentration and turgor pressure. Water always moves from an area of higher water potential to an area of lower water potential. Losing it Water can move into plant cells, and it can move out of plant cells, too. If you put celery or carrot sticks into a salty cup of water, they’ll pretty quickly get limp and rubbery as they lose their turgor pressure. Losing it Because of the dissolved salt, the salty water has a lower water potential than the plant cells. Water flows out of the plant cells, and the cells no longer push up against their cell walls. Turgor pressure is lost, and the vegetables become limp. Losing it If you looked at the cells in the vegetables under a microscope, you’d see plasmolyzed cells. When water leaves a walled cell through osmosis, the cytoplasm collapses, and the plasma membrane pulls away from the cell wall. The collapse of the cell is called plasmolysis..
Load more

Recommended publications
  • Water Content Concepts and Measurement Methods Suat Irmak, Professor, Soil and Water Resources and Irrigation Engineering
    EC3046 December 2019 Soil- Water Potential and Soil- Water Content Concepts and Measurement Methods Suat Irmak, Professor, Soil and Water Resources and Irrigation Engineering Soil- water status is a critical and rapidly changing tion management. In addition, it is important for studying variable that determines and impacts numerous important soil- water movement, chemical transport, crop water stress, factors in production fields such as crop emergence and evapotranspiration, hydrologic and crop modeling, soil phys- growth, water management, water and crop yield productiv- ics, water resources management, climate change impacts ity relationships, and within- field hydrologic balances. Thus, on agricultural water management and crop productivity, its accurate determination dictates and impacts the success of meteorological studies, yield forecasting, water run- off and water management and related agricultural operations. This, run- on, infiltration studies, field traffic and within- field work in turn, affects the attainment of potential yield, as well as the ability and soil- compaction studies, aridity indices, and other reduction of water losses and chemical leaching. Maintaining agricultural and ecosystem functions and practices. Effective optimum soil moisture in the crop root zone also strongly in- irrigation management requires the knowledge of “when” fluences optimum nitrogen (N) uptake by plants, which helps and “how much” water to apply to optimize crop production. to reduce N leaching. Numerous soil moisture measurement Some of the most effective irrigation management decisions technologies are available. None of the methods, however, also include “how” to apply the irrigation water for most are perfectly suited to all operational conditions as each has effective productivity under different climate, soil, crop, and drawbacks and advantages, depending on the application management practices to reduce unbeneficial water losses conditions.
    [Show full text]
  • Master Gardener PUBLISHED by UNIVERSITY of MISSOURI EXTENSION Extension.Missouri.Edu
    Master Gardener PUBLISHED BY UNIVERSITY OF MISSOURI EXTENSION extension.missouri.edu Plants and Their Environment David Trinklein, Division of Plant Sciences lants are living organisms that contain chlorophyll and use it to manufacture Ptheir own food. Their cell walls are more or less rigid and support both the individual cells and the whole structure. Even when plants have reached what we regard as their full, mature size, they continue to expand and develop new leaves, flowers, fruit and shoots. Unlike animals, plants cannot move when the environment changes. They are at the mercy of the climate and the gardener because they are rooted in place. Even though it appears that many plants, especially larger ones, are quite tolerant of change, they sometimes do not show adverse effects until long after the event. For example, tree roots are often damaged or killed by suffocation during building projects or flooding. An established tree may still have strength to leaf out and may appear to thrive for several years. But in its weakened state, the tree is more likely to blow down, become infested or simply decline. To understand why plants respond as they do to natural influences and to cultivation, gardeners must understand something about their structure and how they grow. This publication provides such an introduction. Ways to group plants Uses Gardeners tend to group plants by their horticultural uses: fruits, vegetables, flowers, trees, shrubs, turf and so on. These categories are a convenient way to think and learn about plants. Life cycle Plants can also be categorized by the length of their life cycles.
    [Show full text]
  • Evaluation of the Osmotic Adjustment Response Within the Genus Beta
    July 2008 - Dec. 2008 Osmotic Adjustment Response 119 Evaluation of the Osmotic Adjustment Response within the Genus Beta Manuela Bagatta, Daniela Pacifico, and Giuseppe Mandolino C.R.A. – Centro di Ricerca per le Colture Industriali Via di Corticella 133 – 40128 Bologna (Italy) Corresponding author: Giuseppe Mandolino ([email protected]) ABSTRACT Beta genus includes both industrial and horticultural spe- cies, and wild species and subspecies, which are possible reservoirs of agronomically important characters. Among the traits for which Beta has been recently studied, drought tolerance or avoidance is one of the most important. In this work, relative water content and the osmotic potential in well-watered and stressed conditions of three beet types, one B. vulgaris subspecies and one species other than B. vulgaris, all belonging to the Beta genus, were analysed. In addition, relative water content, succulence index and osmotic potential were measured during a three-week water deprivation period, and the osmotic adjustment was estimated for each Beta accession. The results showed that succulence was higher for B. vulgaris ssp. maritima. It was also shown that all Beta accessions were capable of adjust- ing osmotically, but that the B. vulgaris maritima accession examined had a higher osmotic adjustment value compared to the accessions belonging to cultivated Beta types, and that the accession of the wild species Beta webbiana had a comparatively limited capacity to adjust osmotically. Additional key words: Sugarbeet, sea beet, germplasm, drought, osmotic adjustment rought is one of the greatest limitations for agriculture and crop expansion (Boyer, 1982). Sugarbeet (Beta vulgaris ssp. vulgaris) is aD deep-rooting crop, more adapted to withstand water shortage or nutri- tional deprivation than many other crops (Doorenbos and Kassam, 1979; Biancardi et al., 1998); however, drought stress is becoming a major 120 Journal of Sugar Beet Research Vol.
    [Show full text]
  • Summary a Plant Is an Integrated System Which: 1
    Summary A plant is an integrated system which: 1. Obtains water and nutrients from the soil. 2. Transports them 3. Combines the H2O with CO2 to make sugar. 4. Exports sugar to where it’s needed Today, we’ll start to go over how this occurs Transport in Plants – Outline I.I. PlantPlant waterwater needsneeds II.II. TransportTransport ofof waterwater andand mineralsminerals A.A. FromFrom SoilSoil intointo RootsRoots B.B. FromFrom RootsRoots toto leavesleaves C.C. StomataStomata andand transpirationtranspiration WhyWhy dodo plantsplants needneed soso muchmuch water?water? TheThe importanceimportance ofof waterwater potential,potential, pressure,pressure, solutessolutes andand osmosisosmosis inin movingmoving water…water… Transport in Plants 1.1. AnimalsAnimals havehave circulatorycirculatory systems.systems. 2.2. VascularVascular plantsplants havehave oneone wayway systems.systems. Transport in Plants •• OneOne wayway systems:systems: plantsplants needneed aa lotlot moremore waterwater thanthan samesame sizedsized animals.animals. •• AA sunflowersunflower plantplant “drinks”“drinks” andand “perspires”“perspires” 1717 timestimes asas muchmuch asas aa human,human, perper unitunit ofof mass.mass. Transport of water and minerals in Plants WaterWater isis goodgood forfor plants:plants: 1.1. UsedUsed withwith CO2CO2 inin photosynthesisphotosynthesis toto makemake “food”.“food”. 2.2. TheThe “blood”“blood” ofof plantsplants –– circulationcirculation (used(used toto movemove stuffstuff around).around). 3.3. EvaporativeEvaporative coolingcooling.
    [Show full text]
  • Transport of Water and Solutes in Plants
    Transport of Water and Solutes in Plants Water and Solute Potential Water potential is the measure of potential energy in water and drives the movement of water through plants. LEARNING OBJECTIVES Describe the water and solute potential in plants Key Points Plants use water potential to transport water to the leaves so that photosynthesis can take place. Water potential is a measure of the potential energy in water as well as the difference between the potential in a given water sample and pure water. Water potential is represented by the equation Ψsystem = Ψtotal = Ψs + Ψp + Ψg + Ψm. Water always moves from the system with a higher water potential to the system with a lower water potential. Solute potential (Ψs) decreases with increasing solute concentration; a decrease in Ψs causes a decrease in the total water potential. The internal water potential of a plant cell is more negative than pure water; this causes water to move from the soil into plant roots via osmosis.. Key Terms solute potential: (osmotic potential) pressure which needs to be applied to a solution to prevent the inward flow of water across a semipermeable membrane transpiration: the loss of water by evaporation in terrestrial plants, especially through the stomata; accompanied by a corresponding uptake from the roots water potential: the potential energy of water per unit volume; designated by ψ Water Potential Plants are phenomenal hydraulic engineers. Using only the basic laws of physics and the simple manipulation of potential energy, plants can move water to the top of a 116-meter-tall tree. Plants can also use hydraulics to generate enough force to split rocks and buckle sidewalks.
    [Show full text]
  • The Osmotic Adjustment of Marine Microalgae
    The osmotic adjustment of marine microalgae and the complex role osmolytes play in this process Thesis of Liz Kendall Supervisor Dr. Gieskes Department of Marine Biology, The University of Groningen April 1996 D5O Summary: Algae inhabit a wide variety of both marine and freshwater habitats. These habitats differ in regard to various factors such as chemical composition, the organisms that live there, the light which may radiate into that particular area, the temperature of the sites depending on where the environment is located, just to name a few. One factor that varies from environment to environment is the salinity. This paper will look at the mechanisms utilized by marine algae to cope with the changes in salinity content in their habitats and most importantly how they use different osmolytes to carry out this process. Marine algae "osmotically adjust" themselves to external salinity changes, in a biphasic maimer. Firstly, this includes changes in turgor pressure or large internal water fluxes in response to osmotic gradients. Secondly. an internally regulated osmotic adjustment occurs with the use of both inorganic and organic osmolytes. Compatible solutes are ions and molecules used by man organisms to osmotically adjust and they play a double role in the process of osmotic adjustment. They act as osmolytes and also protect the cellular enzymatic activities under salinity stress. They are called 'compatible solutes" because they protect the cellular enzymatic activity. The main compatible solutes are polyols (including amino acids, carbohydrates and sugars). quaternary ammonium derivatives or tertiary sulphonium compounds. Certain species and taxonomic classes use specific compatible solutes and some even use combinations of them.
    [Show full text]
  • Historical Review
    1 Historical Review INTRODUCTION This chapter presents a brief historical review of progress in the field of plant water relations because the authors feel that it is impossible to fully understand the present without some knowledge of the past. As the Danish philosopher Kierkegaarde wrote, "Life can only be understood backward, but it can only be lived forward," and this also is true of science. The present generation needs to be reminded that some generally accepted concepts have their origin in ideas of 17th or 18th century writers and although others were suggested many decades ago, they were neglected until recently. As might be expected, the importance of water to plant growth was recog- nized by prehistoric farmers because irrigation systems already existed in Egypt, Babylonia (modern Iraq), and China at the beginning of recorded history, and the first European explorers found extensive irrigation systems in both North and South America. However, irrigation was not used extensively in agriculture in the United States until after the middle of the 19th century and little research on plant water relations occurred until the 20th century. Early Research Although plant water relations appear to have been the first area of plant physiology to be studied, progress was slow from Aristotle who died in 322 B.C. to the middle of the 19th century. According to Aristotle, plants absorbed their food ready for use from the soil, and plant nutrition was controlled by a soul or vital principle that ailowed plants to absorb only those substances useful in 2 1. Historical Review growth. This idea only began to be questioned in the 17th century by Jung, van Helmont, Mariotte, and others, and it ~ersistedinto the 19th century.
    [Show full text]
  • Evaluation of Midday Stem Water Potential Amd Soil Moisture Measurement for Irrigation Scheduling in Walnut
    RELATIONSHIPS BETWEEN MIDDAY STEM WATER POTENTIAL, SOIL MOISTURE MEASUREMENT, AND WALNUT SHOOT GROWTH Allan Fulton, Richard Buchner, Cayle Little, Cyndi Gilles, Joe Grant, Bruce Lampinen, Ken Shackel, Larry Schwankl, Terry Prichard, and Dan Rivers. ABSTRACT Measuring midday stem water potential (SWP) with a pressure chamber is an emerging technology for guiding irrigation management in walnut. This study looks at relationships between SWP, soil moisture measurement, and walnut shoot growth in one walnut orchard in Tehama County. The goal was to evaluate the merits for adopting this technology at the farm level. SWP did not correlate well to soil water content measurement without converting the soil water content to soil water depletion. SWP and soil water depletion correlated reasonably well in this study indicating SWP measurement is a valid indicator of orchard water status. Both SWP and soil water depletion correlated equally with average monthly shoot growth. While adaptability of SWP for on-farm use has been questioned for pragmatic reasons such as limiting measurement to mid afternoon hours and in the heat of the day, it may be more precise and practical than measurement of soil water depletion because it is a direct measurement of orchard water status and is not contingent upon the validity of assumptions made to estimate soil water depletion. INTRODUCTION Midday stem water potential (SWP) measurement with a pressure chamber is a relatively new plant-based tool available to assist walnut growers with making irrigation management decisions. In general, growers are more accustom to adopting water budget methods where climate based estimates of crop evapotranspiration (ETc) are used or methods of soil moisture monitoring to guide their irrigation decisions.
    [Show full text]
  • Soil Water Status: Content and Potential by Jim Bilskie, Ph.D
    Soil water status: content and potential By Jim Bilskie, Ph.D. The fundamental forces acting on soil Campbell Scientific, Inc. mwet 94 g water are gravitational, matric, and osmot- ic. Water molecules have energy by mdry 78 g he state of water in soil is described virtue of position in the gravitational force T in terms of the amount of water and sample volume 60 cm3 field just as all matter has potential ener- the energy associated with the forces gy. This energy component is described which hold the water in the soil. The by the gravitational potential component amount of water is defined by water con- of the total water potential. The influence mwater 94gg− 78 tent and the energy state of the water is θ == = −1 of gravitational potential is easily seen g 0. 205 gg the water potential. Plant growth, soil msoil 78g when attractive forces between water and temperature, chemical transport, and soil are less than the gravitational forces ground water recharge are all dependent acting on the water molecule and water m on the state of water in the soil. While dry 78 g − moves downward. ρ ===13. gcm 3 there is a unique relationship between bulk volume 60 cm3 The matrix arrangement of soil solid water content and water potential for a particles results in capillary and electro- particular soil, these physical properties static forces and determines the soil water describe the state of the water in soil in θρ∗ matric potential. The magnitude of the g soil − distinctly different manners. It is impor- θ = = 0.
    [Show full text]
  • Osmoregulation in Cotton in Response to Water Stress' I
    Plant Physiol. (1981) 67, 484 488 0032-0889/81/67/0484/05/$00.50/0 Osmoregulation in Cotton in Response to Water Stress' I. ALTERATIONS IN PHOTOSYNTHESIS, LEAF CONDUCTANCE, TRANSLOCATION, AND ULTRASTRUCTURE Received for publication June 13, 1980 and in revised form October 13, 1980 ROBERT C. ACKERSON AND RICHARD R. HEBERT Central Research and Development Department, Experimental Station, E. L du Pont de Nemours and Company, Wilmington, Delaware 19898 ABSTRACT paper in this series defines the role of specific cellular carbohy- drates in stress adaptation (2). Cotton plants subjected to a series of water deficits exhibited stress adaptation In the form of osmoregulation when plants were subjected to a subsequent drying cycle. After adaptation, the leaf water potential coincid- MATERIALS AND METHODS ing with zero turgor was considerably lower than in plants that had never Plant Material. Cotton (Gossypium hirsutum L. Tamcot SP37) experienced a water stress. The relationship between leaf turgor and leaf plants were grown from seed in controlled environment facilities water potential depnded O leaf age. as described (3). When the fifth leaf above the cotyledons was Nonstomatal factors severely limited photosynthesis in adapted plants about 75% expanded, one set of plants was subjected to repetitive at high leaf water potential. Nonetheless, adapted plants maintained pho- water stress cycles while another set was well watered. Each stress tosyPnthesis to a much lower leaf water potential than did control plants, in cycle consisted of allowing plants to dehydrate until midday leaf part because of increased stomatal conductance at low leaf water poten- water potentials reached approximately -20 bars.
    [Show full text]
  • Irrigation Scheduling by Soil Water Potential
    Irrigation scheduling by soil water potential Clinton C. Shock, Professor and Superintendent, Oregon State University, Malheur Experiment Station, 595 Onion Ave., Ontario, OR, email [email protected] Abstract. One of the fundamental ways to schedule irrigation is through the monitoring and management of soil water potential (SWP). Soil water tension (SWT) is the force necessary for roots to extract water from the soil and growers find it easier to deal with the positive units of SWT rather than the negative units of SWP. With the invention of tensiometers, SWT measurements have been used to schedule irrigation. There are seven different types of field instruments used to measure SWT, either directly or indirectly. Specific SWT criteria for irrigation scheduling have been developed for the production of individual vegetable crops, field crops, trees, shrubs, and nursery crops and for the management of landscape plants. A review of the known SWT criteria for irrigation scheduling will be presented. Keywords. Soil water tension, Tensiometer, Granular matrix sensor Why Measure Soil Water Tension The lack of water in plant-top tissues is transmitted through the plant, down into the roots, and into the soil. The measurement of soil water tension can be closely related to the stress experienced by the plant tissues, and in these conditions irrigation scheduling based on soil water tension can be directly related to plant performance. The use of a soil water tension measuring device provides a continuous measurement analogous to the force (suction) necessary to extract water from the soil. When growers irrigate too infrequently and with too much water, product yield and quality is lost (Tjosvold and Schulbach 1991) and water and nutrients are lost, with the potential of environmental harm.
    [Show full text]
  • BIOL 221 – Concepts of Botany Topic 12: Water Relations, Osmosis and Transpiration
    BIOL 221 – Concepts of Botany Topic 12: Water Relations, Osmosis and Transpiration: A. Water Relations Water plays a critical role in plants. Water is the universal solvent that allows biochemical reactions to occur in all organisms, but that is not the only importance in plants. Water moves from the roots to the shoots and to every cell in between. Water movements across membranes (osmosis) results in the development of turgor pressures (positive pressures) in plant cells. These turgor pressures are what keep the primary plant body upright on land and, when they are lost, the plant wilts (cells become flaccid). In addition, the turgor pressures in young developing plant cells is directly responsible for the expansion of these cells. Therefore, growth of the plant depends on the movement of water to growing regions like the apical meristems. In addition, water movements facilitate nutrient transfer (minerals) from the roots to the photosynthetic tissues. Water in the phloem keeps important photosynthate compounds in solution for transport from sources (photosynthetic leaves) to sinks (non-photosynthetic organs, rapidly growing regions). So obviously water is extremely important to the health of a plant. In today’s lab you will have a chance to investigate the importance of water uptake and movement at the cellular and whole plant levels. Enjoy! B. To Transpire or Not to Transpire… Water moves through the plant continuously due to severe differences in water potential between the soil, the plant and the atmosphere. The xylem vascular tissue takes advantage of the physical properties of water (surface tension, cohesion, adhesion) in order to move water from the roots to the shoot.
    [Show full text]