Mass Transport in Plants

11 Key excerpts on "Mass Transport in Plants"

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  eBook - PDF

  Ecological Processes Handbook

  • Luca Palmeri, Alberto Barausse, Sven Erik Jorgensen(Authors)
  • 2013(Publication Date)
  • CRC Press

    (Publisher)

  85 © 2008 Taylor & Francis Group, LLC 7 Mass Transport 7.1 Introduction Chapters 1 and 6 pointed out that an ecosystem is influenced by matter and energy exchanges with the surrounding environment, that is, transbound-ary fluxes that link the ecosystem to its neighboring systems. An ecosystem is also affected by the relationships between its abiotic and biotic compo-nents, which can be represented as flows of energy, matter, and information. For this reason, transport phenomena represent fundamental ecological pro-cesses underlying the functioning of any kind of ecosystem. In this chapter, the physical processes that determine the transport of mass found in fluids toward, from, or within ecosystems are described; the transport of energy and the role of energetic factors in physical processes will be illustrated in Chapter 8. Here, mass means the amount of any kind of matter whose physical trans-port in fluids (air and water) is relevant for the functioning or for a particular characteristic of an ecological system. Typical examples are not only chemi-cal elements and substances, such as food and resources (e.g., biomass, car-bon, and nutrients), but also toxins and pollutants. Even living beings can be transported, along with the substances they carry in their own body tis-sues, such as nutrients and bioaccumulated contaminants, as well as with the ecological processes that they carry out (predation, competition, etc.; see Chapters 16 and 19). For instance, plankton are, by definition, those drift-ing organisms that are transported by water currents. Why should mass transport in fluids be focused on? Fluids are a major constituent of most eco-systems and typically represent their most dynamic media; therefore, mass transport can strongly influence the availability or concentration of many key substances in space and time. Indeed, mass transport plays an impor-tant role in the biogeochemical cycles of key ecological elements, which are detailed in Chapter 12.

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  Physiology of Woody Plants

  • Paul Kramer(Author)
  • 2012(Publication Date)
  • Academic Press

    (Publisher)

  Translocation Introduction 373 Water Transport 374 Composition of Xylem Sap 375 Mineral Transport 376 Upward Movement 376 Recirculation of Minerals 377 Control of Mineral Uptake 379 Translocation of Organic Compounds 379 Carbohydrates 380 Growth Regulators 390 Herbicides 390 Viruses 390 Interplant Translocation 391 Symbiotic and Parasitic Associations 391 Root Grafts 392 Ungrafted Plants 394 Mechanisms of Phloem Translocation 394 Sieve Tubes of Angiosperms 395 Sieve Cells of Gymnosperms 396 Longevity of Conducting Elements 396 Driving Forces in Translocation 397 Control of Phloem Transport 400 General References 401 INTRODUCTION The success of plants more than a few centimeters in height depends on the move-ment of water, minerals, and some organic compounds from their roots to their shoots and the movement of carbohydrates and other organic compounds from their shoots to their roots. Continued growth requires that an adequate supply of water, mineral nutrients, organic nitrogen compounds, and certain growth regulators be available at the various meristematic regions. Thus the transport of these substances to the regions where they are being used as building materials and substrates for respiration is as important for growth as the synthetic processes which produce them. 373 374 11. Translocation In small, relatively undifferentiated organisms every cell can carry on all essential processes and no cell is far from a source of raw materials. In such low-growing plants as mosses and liverworts diffusion, perhaps aided by cytoplasmic streaming, suffices for the short-distance translocation that is necessary. However, rapid, bidirectional, long-distance translocation upward and downward is essential for the existence of large land plants such as trees because root growth depends on sugar and probably growth regulators from the leaves and the leaves depend on the roots for their supply of water, mineral nutrients, organic nitrogen compounds, and some growth regulators.

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  eBook - ePub

  Principles of Horticulture: Level 3

  • Charles Adams, Mike Early, Jane Brook, Katherine Bamford(Authors)
  • 2015(Publication Date)
  • Routledge

    (Publisher)

  6    

  CHAPTER

  Level 3

  Transport in the plant

  Figure 6.1 A blue dye has been used to show the pathway of water movement in the xylem of a celery stem and leaves. Note the staining of the xylem tissue in the vascular bundles of the stem cross section, the continuity of xylem vessels up the stem itself (cortex removed) and the distribution of xylem in the veins of the leaves

  This chapter includes the following topics:

  • Movement of substances in the plant

  • Water movement between cells

  • Water movement through the plant

  • Factors affecting transpiration

  • Plant adaptations to low water environments

  • Stomata

  • Uptake and movement of mineral nutrients

  • Phloem translocation and the movement of sugars

  • The balance between photosynthesis, respiration and transpiration

  Principles of Horticulture. 978-0-415-85909-7 © C.R. Adams, M.P. Early, J.E. Brook and K.M. Bamford. Published by Taylor & Francis. All rights reserved.

  Without effective uptake and transport of gases, water and dissolved substances such as minerals, sucrose and plant growth regulators, plants would not be able to function. The exchange of gases necessary for photosynthesis and respiration is described in Chapter 5 . The movement of water and dissolved substances (translocation) takes place in two specialized tissues, the xylem and the phloem, whose structures are described in Chapter 3

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  Handbook of Chemical Mass Transport in the Environment

  • Louis J. Thibodeaux, Donald Mackay, Louis J. Thibodeaux, Donald Mackay(Authors)
  • 2010(Publication Date)
  • CRC Press

    (Publisher)

  A brief description of plant uptake models is followed by illustrative examples of plant uptake. It should be appreciated that the state of the science regarding mass transport of organic con-taminants into plants from soil is much less developed than other transport processes described in this handbook. This reflects both a relative lack of comparable empirical data and the number and complexity of the plant physiological and environmental variables associated with the uptake processes as discussed by Legind and Trapp (2009) and McKone and Maddalena (2007). 14.2 ROOT UPTAKE AND TRANSLOCATION Transpiration is defined as the root uptake of water, the subsequent transfer to leaves, and loss due to evaporation, and it drives the passive root uptake of organic compounds. Mass Transfer from Soil to Plants 391 Water loss during transpiration occurs mainly through the leaves as the stomates open to allow the exchange of CO 2 and O 2 during photosynthesis. However, water loss can also occur through stems, flowers, and fruits. Dissolved organic solutes are drawn toward the roots along with water and nutrients (e.g., Bowling, 1979; Briggs et al., 1982; Bromilow and Chamberlain, 1995; McFarlane, 1995). For organic compounds with relatively high Henry’s law constants, movement to the roots through the soil vapor phase may also be important. Uptake is facilitated by root hairs that penetrate into the soil pores and influence the volume of soil that is available for chemical uptake. The two main pathways that water and organic chemicals follow into the roots are referred to as symplastic and apoplastic . Symplastic transport is characterized by water and solutes moving through the plasma membranes and interior of individual root cells, while apoplastic transport occurs when water and solutes pass between the roots cells until reaching the Casparian strip, a waxy band associated with the endodermis as illustrated in Figure 14.1.

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  Transport of Nutrients in Plants

  • A. J. Peel(Author)
  • 2013(Publication Date)
  • Butterworth-Heinemann

    (Publisher)

  The pathways of long distance transport 35 The movement of solutes in radial and tangential transport systems Circulation of nutrients within plants In dealing with the pathways of solute transport within the plant, we are not only concerned with the long distance, longitudinal systems—the phloem and xylem—but also with the systems which move materials over relatively short distances. Clearly, it would be of little use to the plant to be able to transport materials from the roots to the leaves and vice versa, if it were not also able to convey nutrients to the cells of the stem which lie some little distance lateral to the main transport pathways. There is ample evidence in the literature for the presence of radial and tangential transport systems which move nutrients, not only from vascular to non-vascular tissues, but also between the vascular tissues themselves. Much of the evidence for the functioning of radial and tangential systems has been obtained from experiments in which the circulation patterns of nutrients have been studied. As long ago as 1877, Hartig proposed that a circulation of carbohydrates might take place on an annual basis in trees. He concluded that assimilates moved from the leaves into the bark, where they were stored in the parenchyma and ray cells during the winter. In spring these assimilates were re-mobilised and moved into the xylem vessels, whence they ascended in the current of water. It has also been known for a considerable time that nitrogenous substances can be re-exported from senescing leaves to parts of the plant which are still growing. The data of Mason and Maskell (1931) indicated that certain nutrients such as phosphorus and potassium could be circulated within the plant without an intervening storage period. More recently, O. Biddulph et al. (1958) have shown that some solutes can circulate freely.

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  Mechanisms of Plant Growth and Improved Productivity Modern Approaches

  • Amarjit Basra(Author)
  • 2021(Publication Date)
  • CRC Press

    (Publisher)

  There are two auxiliary systems which can at times become very important in the life of the plant: the rays and the xylem. Ray tissue seems to operate simultaneously as a circulatory link between xylem and phloem and as a temporary and seasonal store for photoassimilates. The xylem seems to be utilized as a passive “piggyback” transport system when the transpiration stream is appropriately directed toward target tissues, especially when growth starts to accelerate at the beginning of the growing season. Up to now these transport systems have only been examined in a relatively few species. Until many more have been studied it will be impossible to gauge their importance in plants generally; nevertheless the importance of such studies for understanding the growth of timber in forestry cannot be underestimated.

  Obviously, the transport of photoassimilates is of immense importance in controlling crop yield. Potentially large gains in yield should flow from a better understanding and manipulation of the processes involved. An unavoidable by-product of such research is the better understanding of the physiology and biochemistry of higher plants, on which civilization is so heavily dependent.

  REFERENCES

  • 1 . T. G. Mason and E. J. Maskell, Annals of Botany, 50: 23 (1931).
  • 2 . H. H. Dixon, Scientific Proceedings of the Royal Dublin Society, 20: 487 (1933).
  • 3 . K. Esau, Encyclopedia of Plant Anatomy, 5, Gebruder Borntraeger, Berlin and Stuttgart, p. 38 (1969).
  • 4 . B. Hylmo, Physiol. Plant., 6: 333 (1953).
  • 5 . J. S. Pate, Encyclopedia of Plant Physiology, 1 (M. H. Zimmermann and J. A. Milburn, eds.), Springer Verlag, Berlin, Heidelberg, and New York, p. 451 (1975).
  • 6 . J. S. Bonner, Plant Biochemistry, Academic Press, New York, p. 328 (1950).
  • 7 . J. W. Marvin, The Physiology of Forest Trees (K. V. Thimann, ed.), Ronald Press, New York, p. 95 (1958).
  • 8 . J. J. Sauter, W. Iten, and M. H. Zimmermann, Can. J. Bot., 51: 1 (1973).
  • 9 . J. A. Milburn and P. E. O’Malley, Can. J. Bot., 61: 3100 (1984).
  • 10 . M. T. Tyree, Plant Physiol., 73: 277 (1983).
  • 11 . J. S. Pate, Transport of Photoassimilates (D. A. Baker and J. A. Milburn, eds.), Longman, Harlow, Essex, U.K., p. 138 (1989).
  • 12 . E. Münch, Die Stoffbewegungen in der Pflanze, Fischer, Jena (1930).
  • 13 . J. Kallarackal and J. A. Milburn, Austral. J. Plant Physiol., 56:

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  Marschner's Mineral Nutrition of Higher Plants

  • Horst Marschner(Author)
  • 2011(Publication Date)
  • Academic Press

    (Publisher)

  phloem loading) and water is sucked into the phloem, creating a positive internal pressure. This pressure induces a mass flow in the phloem to the sites of lower positive pressure caused by removal of solutes from the phloem. Therefore, flow rate and direction of flow are closely related to phloem unloading at the sink. This type of pressure-driven mass flow in the phloem differs from that in the xylem in three important ways: (i) organic compounds are the dominant solutes in the phloem sap, (ii) transport takes place in living cells, and (iii) the unloading of solutes at the sink plays an important role.

  Figure 3.9 Cross-section of a vascular bundle from the stem of maize. Inset: Sieve tube with sieve plate pores and ‘P-protein’. Redrawn from Eschrich (1976).

  For nutrients, the main sites (sources) for phloem loading are located in the stem and the leaves. These supply nutrients to growth sinks (shoot apices, fruits, roots) and allow nutrient cycling within the plant. An example of sink-regulated transport of a nutrient is shown in Fig. 3.10 for P. After application to one of the two mature primary leaves, the labelled P is transported to the shoot apex and the roots whereas transport to the other primary leaf is negligible. In contrast, Na is not transported to the shoot apex but moves exclusively downwards (basipetally) to the roots where it is confined to the basal zones (Fig. 3.10 ). From here a considerable net efflux of Na takes place ( Lessani and Marschner, 1978 ). This example reflects the role of phloem transport in cycling elements within the plant and specifically in prevention of Na accumulation in the shoots of natrophobic plant species. The capacity of bidirectional, ion-specific, long-distance transport is based on the physio-logy and anatomy of the phloem and its elements.

  Figure 3.10 Re-translocation of labelled P ( 32 P) and Na ( 22 Na) after application to the tip of a primary leaf of bean. Autoradiogram, 24 h after application.

  Within the phloem, the sieve tube elements are associated with companion cells and parenchyma cells (Fig. 3.9 ). Some of these individual sieve tube elements are stretched end to end in a long series, forming the sieve tubes which are connected by pores (inset, Fig. 3.9

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  The Physiology of Flowering Plants

  • Helgi Öpik, Stephen A. Rolfe(Authors)
  • 2005(Publication Date)
  • Cambridge University Press

    (Publisher)

  P. (2001). Symbiotic nitrogen fixation and phosphorus acquisition: plant nutrition in a world of declining renewable resources. Plant Physiology , 127 , 390–7. 132 MINERAL NUTRITION Chapter 5 Translocation of organic compounds 5.1 Introduction Flowering plants are described as being autotrophic , ‘self-feeding’, capable of synthesizing all their organic material via photosynthesis. But a flowering plant is a complex organism with cells and organs specialized for diverse functions, and only the green photosynthetic cells are truly autotrophic; they must accordingly supply all the non-photosynthetic parts with organic carbon. Over small distances, i.e. between individual cells and within small groups of cells, chemicals can move by diffusion through plasmodesmata, or across plasma membranes by diffusion and by active transport. But organic mater-ials must move for long distances; the growing tips of the roots of a tree are many metres away from the nearest photosynthetic leaves and even in a herbaceous plant diffusion would be too slow for the distances involved. We have already seen (Chapter 3 ) how water moves in plants over long distances in a specialized transport tissue, the xylem. The subject of this chapter is the long-distance, multi-directional movement or translocation of organic compounds which takes place in the phloem. 5.2 Phloem as the channel for organic translocation 5.2.1 Evidence for translocation in the phloem In flowering plants, the xylem is regularly associated with the phloem , the two together making up the vascular tissues. In young organs the two tissues are in contact; when secondary growth occurs they become separated by the vascular cambium, the meristem which then adds xylem to one side and phloem to the other. In woody stems, where the vascular tissues form complete cylin-ders, it is fairly easy to cut through the outer stem tissues down to the vascular cambium and to remove the ‘bark’, which includes the

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  Cambridge O Level Biology 5090

  • Azhar ul Haque Sario(Author)
  • 2023(Publication Date)
  • tredition

    (Publisher)

  Picture the journey of sucrose and amino acids as a relay race. The leaves, after producing these substances, pass them to the phloem. The phloem then races through the plant's structure, passing through stems, reaching down into the roots, or climbing up to the fruits and seeds. This journey isn't always a downhill ride. Sometimes, the phloem has to transport these substances up against gravity, like delivering food to the top floor of a tall building.

  The fascinating part of this process is the pressure flow hypothesis, which explains how the movement happens. It's like a pressure cooker situation. The loading of sucrose into the phloem at the source creates a high pressure. Water follows, rushing in, and this creates a flow. The sucrose and amino acids are swept along in this flow, moving from the high-pressure area (the source) to a lower pressure area (the sink).

  When they reach their destination, these nutrients are offloaded. The sink uses the sucrose for energy or stores it for later use. The amino acids are used to build proteins that help the plant grow, fight diseases, or even prepare for adverse conditions.

  In summary, translocation is not just a movement; it's a lifeline for the plant. It ensures that every part of the plant gets what it needs, when it needs it, much like a well-coordinated delivery system ensuring that every part of a city gets its essential supplies. This remarkable process showcases the intricate and efficient ways in which plants sustain themselves and thrive.

  Understanding the arrangement of tissues in transverse sections of non-woody dicotyledonous roots and stems provides valuable insight into plant biology and function. Let's explore the positions of the xyleem, phloem, and cortex in these plant parts.

  Non-Woody Dicotyledonous Roots

  Cortex: The outermost layer of the root, the cortex, plays a crucial role in the storage of food and the absorption of water and nutrients from the soil. It is a region with loosely packed cells, allowing for easy passage of water and minerals.

  Phloem: Situated inside the cortex, the phloem forms a part of the vascular system of the root. This tissue is responsible for transporting organic nutrients, primarily sugars, from the leaves to other parts of the plant. In dicotyledonous roots, phloem is typically found in patches interspersed around the central core of xylem.

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  Transport and Transfer Process in Plants

  • I Wardlaw(Author)
  • 2012(Publication Date)
  • Academic Press

    (Publisher)

  Ann. Bot. (N.S.) 32, 327-46. Turner, J.F. (1969). Starch synthesis and changes in uridine diphosphate glucose pyrophosphorylase and adenosine diphosphate glucose pyrophosphorylase in the developing wheat grain. Aust. J. Biol. Sei. 22, 1321-7. Walker, D.A. (1974). Chloroplast and cell-The movement of certain key substances, etc. across the chloroplast envelope. In: Plant Biochemistry ed. by D.H. Northcote, Butterworths, London Biochemistry Series One, Volume 11 pp. 1-49. 83 This page intentionally left blank CHAPTER 8 Nutrient Uptake by Roots and Transport to the Xylem: Uptake Processes M.G. Pitman School of Biological Sciences 3 University of Sydney y N.S.W. Australia INTRODUCTION This paper is intended to introduce the following papers by Dr. Läuchli on transport in the symplasm and by Dr. Cram on regulation of uptake, as well as discussing the absorption of nutrients by plants. Uptake by the plant is a complex process because it is affected by external factors such as soil or nutrient avail-ability, by the flux of water through the system and by the organisation within the root. This complexity is summarised in Figure 1. The root operates as a system for absorption of ions from the soil and for supply of ions to the shoot, but it is convenient to separate the overall activity into components, which have particular characteristics. For example, the absorption is a property primarily associated with the outer cell membranes, and there is much information about this process from different kinds of study. Within the root ions can be accumulated to high concentration in cell vacuoles or pass in the symplasm into the stele and event-ually to the xylem. This process of transport across the root and release to the xylem is discussed further by Dr.

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  Plant Physiology 9

  A Treatise: Water and Solutes in Plants

  • F.C. Steward(Author)
  • 2012(Publication Date)
  • Academic Press

    (Publisher)

  Before considering hypotheses of translocation in detail, it is desirable to contrast the physical bases for solute movement and to compare diffusion, surface flow, and bulk flow, sometimes termed mass flow. 1. Diffusion It has long been realized that the thermal agitation and movement of molecules by diffusion is far too slow a process to be involved in long-dis-tance transport. Tyree and Dainty (291) have pointed out that where bulk flow of fluid is rapid and the product of solute concentration and mean velocity greatly exceeds (say by 100 times) the product of diffusion coeffi-cient (usually of the order of 10~ 5 c m -2 s -1 ) and concentration gradient, then the contribution of diffusion can be ignored. But diffusion may be significant in two other ways. First, the dimensions of the sieve tube and the order of velocity of movement along it are such that because of lateral diffusion solute concen-tration across the sieve tube radius will be uniform (291) and local gra-dients can therefore be ignored. Diffusion is also important in transport up to and away from the sieve tube. No matter what the mechanism of transport along the sieve tube or the velocity, ultimately the supply of translocate to cells can be limited by diffusion through the apoplastic or symplastic pathway. Clearly, the shorter the diffusion path, the less likely such a limitation is to be impor-tant, and the fact that there is little or no evidence for sink activity being restricted by translocation suggests that vascular development at the sink may serve to limit the length of the diffusion path. IV. Mechanisms of Translocation 6. PHLOEM TRANSPORT 511 2. Surface Flow The application of the principle of surface flow to explain translocation originally introduced by Mangham (190) and Van den Honert (295) has been recently discussed by a number of workers (3,83,311). The phenom-enon involves the spreading of surface-active molecules along a surface to form a monolayer.

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