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Chapter Transport of Food and 1 Minerals in Plants Chapter Objectives In this chapter, you learn about: wil...

Chapter Transport of Food and 1 Minerals in Plants Chapter Objectives In this chapter, you learn about: will Absorption of water by roots Root pressure Absorption of mineral salts by roots Mechanism of transpiration and its significance Osmosis and diffusion Translocation What will happen if plants and animals do not get water for a few days? Discuss. INTRODUCTION Plants obtain energy from food to perform their other parts.Thus, there are mainly two types of daily vital activities. They obtain their own food conduction processes in plants: by the process of photosynthesis in the presence 1. One that carries water and minerals from of sunlight and chlorophyll by taking in minerals roots to other parts. and water from the soil and carbon dioxide from 2 One that carries food prepared in leaves to the air. The end products of the process include other parts. glucose and oxygen. In this chapter, we will discuss about transport Transportation is a process in which a substance process in plants. absorbed or produced in one part is taken to ABSORPTION OF WATER BY ROOTS Bud Glucose moves up to the growing bud Plants can absorb water through their entir surface.However, since water is mainly available Water and in soil, a well-developed root system is present Leaf minerals to absorb water. Other functions performedby from soil roots are: Stem Glucose made by photosynthesis Anchorage of plant to the soil. Site of storage of food and other nutrients. Glucose moves down Soil to the growing root Water is an importantcomponent for a plant. It plays a significant role in: Water and minerals are taken up by roots Carrying out various life processes such as photosynthesis and transpiration. Fig. 1.1 Transportation of substances in plants (Diagrammaticrepresentation) Absorbing minerals from the soil.  Siructure and Speciality of Root Hair , increases, the surface arca als0 incrcascs, andthe Root is covered at the tip by root cap,.which plants absorb more water and minerals protects the delicate apex behind the cap as the root invadesdeep Osmosis in soil(Rootsare covered by a single-celled Osmosis is a distinct type of transmission of layer called epidermis (The epidermal cells have finger-like tubular water that gçcurs through a semipermeable outgrowth known as root hair membrane. is defincd as the moement that aid in of increasing the surface area for twater (orolvent)across semipermeable bsgyption of membrane water. from a region of its bigb concentration to a region of its low The As the plants grow, their roots branch and concentration concentration of water is higher in soil,thus water moves from rebranch and get fixed in the thetips of soil, At soil (higherconcentration) to root cells (lower roots, a_large number of cells absorb water and concentration) through plasma membrane, nutrients fromthe soil/These cells have a Salt Water semipermeable plasma membrane. Plasma membrane has tiny poresthat Roots allow only selected materials and water molecules to pass through it)by a process known as osmosis. (The amount of water absorbed is proportional Fig.1.3 Movementof molecules across to the number semiperneable membrane of root hafr Eg.1.2 Roots in in plants As thenumber of root ha plants ACTION TIME 1 Activity: To study the transportation process and functioning of cells in a potato. Procedure: Peel a potato, Cut it into two pieces and slice its bottom part. Make a deep hole on the top part of the potato and make a potato Cup. Put some sugarsolution the cup. in Make a note of the of the sugar solution. level Sugar Solution Pierce the outer wall of the potato with pin. a Place the potato in a container with water in such a way thatit is partly immersed in water. Leave it undisturbed for some time. Observation: The level of the sugar solution increases. Water Conclusion: This is because water moves from glass beaker (lower concentration) to potato (higher concentration), through a selectively permeable membrane. Thus, the process of osmosis has taken place. 2 Teaching Tip:The meaning of surface tension can be explained to students.(Surtacetension is the energy of work, required to increasethe surface area of a liquid due to intermolecularforces.)  Diffusion 4, Osmosis involves rmovernent of water across wpyoseoses (semipermeable/ Diffusion is a process of movement of'molecules from permeable)membrane. a region of bigber concentration to a region of louwer 5 (Diffužon/Osmosis)is concentration )(A) movernent of substances Concentration from high to low Active Transport 6. Active transport takes place through carrier htive transport is defined as the transport of (seats/proteis). substances across the cell membrane against the concentration gradient) I requires input of cONDUCTING TISSUE energy and does not take place impulsively. The A tissue is a group of cells that performsa specialised transport of substances takes place from low ficnction in organisms. These are commonly concentration to high concentration, or uphill known as conducting tissues. The conducting transport across the cell membrane.The energy tissues are 9f two types. They are xylem and is usually obtaincd from respiring root cells. phloem. (The xylem arries water and nutrient / Active transport is unidirectional and the minerals from the roots to the leaves. Che phloem transport always takes place through carrier carries food from leavs to various pafts of theplant proteins present in themembranc. Carrier protein INFO HUB Concentration gradient Water does not travel through xylen vessels Outside cell by osmosis. Osmosis involves thenovement D of water across cell membranes%ylem cells. Cell do not have any living contents]when mature, membrane so there will be no menbrane42 Capillary action pulls water from thec roots to Inside cell the leaves. On absorption, water moves from the outer layer of the epidermis to the specialised tissue called xylem. Xylem are pipe-like vesscls Fig. 14 Movement of molecules by active transport in plants through which water and minerals enter/Each vessel is made up of thick walls and Quick Check1 clongated cells. These tissues form a continuous A. Fill inthe blanks. network within the plants,and spread across the The process of preparation of food by plants 1, roots, stem, branches and leaves.Thus, water in the presence of light is called and dissolved minerals are transported in the (photosynthesis/ transpiration). form of sap. 2 (OsmosisDiffusion) (The sap moves in an upward direction against ocCurs through a sernipermeablenembrane. of the plant.This the gravity to reach the leaves upward movement of sap (from the root tothe 3. Root hair increase the (anchorage/surfact area) for absorption. crown) is called ascent of sap (Fig. 1.5). It is aided by transpiration and root pressure) Teaching Tip: Active transport can be demonstrated using a video. Students can be asked to work in groups and design a nodel on ít. |Concentrationgradient: Fall in concentration he root pressure pushes the water up towards the stem.The capillary actionthen further pushes the water up the narrow tubes of xylem.) This rising ofwater through the narrow tubes of the xylen is called capillary action. The factors that are responsible for ascentof sap are: 1. Cohesion: It is the mutual attraction between water molecules. 2. Adhesion: It involves attraction of water molecules to the surface(surface of elements of xylem). TRANSPIRATION Xylem sap Water molecules Atmosphere Adhesíon Cell Xylem wall cells Sap of Ascent Cohesion by Cohesion, hydrogen Adhesion bonding in the xylem INFO HUB Water Cohesive molecule and adhesive properties of Root water mnolecules help to form Soil an unbroken ContinuOus water Water column in the Water uptake from soil xylem.. 4 Teaching liquid in a Tip: capillary Fig. 1.5 Ascent of sap Hydrogen bonding can be tube orabsorbent briefly material to explained to rise or fall as students. a result | Capillary action: The tendency of of surface tension a  Quick Chect 2 Match the following: Column A Column B 1. Tissue a Pulls water from roots 2. Xylem b, Carries food from leaves to other parts 3. Phloem C Carries water from roots to leaves 4. Capllary action d. Upward movement of water and minerals frorm the root to the croWn 5. Ascent of sap e. Group of cells Cuticular transpiration INFO HUB Cuticle is the Water potential of root cell is less than that multilayered waxy deposit that of outside soil which causes movement generally covers of the leaves of theplants. Even water into the root through osmosis. This though it is impermeable to water, but certain results in root pressure which pushes water up the xylem. amount of water can pass through The it amount of water lost depends on the thickness of cuticle. TRANSPIRATION Lossofwater from the plant in the form ofwater Cuticle vapour is known as. transpiration. Based on the -Upper region from which epidermis it is taking place, it can be -Palisade of following types-Lenicular, Cuticular and cells Stomatal, Spongy cells Lenticular Xylem transpiration -Phloem Lenticels are small openings in the bark of young Lower oranches, cork of woody stems and fruits Very small epidermis amount of wateris lost through the lenticels. Fig.1.7 Leafanatomy Lenticel INFO HB In dry conditions when the stomataof leaves with thin cuticle close, cuticular transpiration becomes significant StomatalTranspiration Transpiration mainly takes place through th Cross-section of a stem stomata (singular, stoma) which areminut showing lenticels Fig. 1.6 pores present in the JeavesJach stomais Lenticular transpiration Water potential: The energy surrounded by two bean-shaped guard cells the sarnple to a requred, per quantity reference part of of water, totransport infinitesimat quantity of water from pure free water (The main function of stomata is to system of the plant is removed and pot allow its carbon dioxide to enter into the covered with the polythene bag. The leaves for is photosynthesist simultaneouslyfunctions presence of water droplets on the innerside to prevent excessive water loss.)Loss of water of jar A after some time shows transpiration vapour through stomata is known as stomatal occurring from leaves. transpiration.(Maximum amount of transpization- 2. Cobalt chloride: Two strips of filter paper in a plant bady occurs througb stomata, soaked in 2% solution of cobalt chloride Guard cells and are perfectly dried under sunlight. Cobalt chloride paper is blue in colour when it is dry, and becomes pink when-it -Stomata absorbs moisture. Due to this characteristic LChloroplast feature, it acts as a chemical indicator in this experiment. This method is used to compare the rate of Open stoma a. b. Closed stoma transpiration between the two surfaces of Fig. 1.8 Open and close of stomata in plants the same leaf suggesting that more stomata are present in the lower surface of the leaf Experiments forDemonstrating Transpiration In this method, a piece of dry blue cobalt Transpiration can be demonstrated by the chloride paper is kept on a leaf. It is covered followingmethods: by glass slides with clips.The colour ofcobalt chloride changing from blue to pink shows 1. Polythene bag:The process oftranspiration transpiration. The time taken for this change can be demonstrated by covering a well determines the rate of transpiration. watered potted plant with a polythene bag Rubber Cobalt chloride and firmly tying the knot at the mouth paper band (on upper surface) to prevent any water loss from the plant. The setup is kept in a bell jar in sunlight. Label this as jar 'A.A control experiment Leaf on Cobalt Paper Paper is done simultaneously in which theshoot a potted Glass chloride paper (turned (turned plant more O slides (on lower less pink) pink) After placing the bell jars in sunlight for 1 hour surface) Control Fig. 1.10 Cobalt chloride turns pink to show that Bell jars transpiration takes place INFO HUB Potted plant The colour change on the lower surface of Polythene the leaf is faster than on the upper surface as, bags generally, there is more number of stomataon the lower surface than on the upper surtace. Fig. 1.9 Release of water vapour by plants  of Transpiration the Importance and directlystimulates the soil Transpiration 1. Transpirationof water from whích Factors Affecting by several is affected absorption (tension) transpiration light, pressure The rate of Temperature, a negative This is called factors. of water exerts in xylem. and internal external and availability pulls water upwards the wind speed on which pull. humidity, factors plant the five external transpirational of the in soil are thc temperature rises oftranspiration depends. oftranspiration 2. It regulates of the plant for the Sun tempcrature body. The rate The rate cnergy from 1. Temperature: with incrcase in temperatureHigh water as it absorbs ofwater from of Evaporation rid of the increases evaporation favours photosynthesis. in getting temperature helps heat the plant body preventing from the leaves. day energy, thus remain open during excess heat Stomata takes leaves. 2. Light: of most of thetranspiration injury hence time, stomata and transportation night, theAt helps in absorption and the day. 3. plant body, the place during amount of parts of so very little minerals to all of closed, remain or lenticular and development cuticular the growth water is lost by thus belps in of light is If the intensity the plant. duration, transpiration. fora longer they remain turgid. water, high andit isprovided of the surrounding 4 When cells absorb the shape and then the temperature in maintaining This helps of whichtransprationo increases as a result of the plant body. structure also increases. content of air The actual water 3. Humidity: expressed as GUTTATION such humidity, which is of low evaporation 1s known as the periods vapour /During droplets at night, water in difference vapour pressure. The morning or the atmosphere and as early special vein openings can be observed around pressure between of the leaf atfects root the spaces such periods, intercellular (hydathodes) During With increase in humidity up to transpiration. is very high, thus water is forced pressure the humidity is tow, This ranspiration decrease,If and comes out ofthe plantbody. in the surroundingthe xylem that is, vapour pressure that is collected(This loss of is is the excess water is low, the transpiration atmosphere state is known as guttation. Raater in the liquid favoured. in wind peed Wind spced: Increase increases the rate of transpiration. Ifless wateris 5. Availability of water in soil: avaiable in the soil, the rate transpiration of decreases; as a result, the stomata will be partially or completely closed. Fig. 1.11 Loss of water by plants through guttation Turgid: Abnormally distended especially by fluid or gas  Hw Quick Check3) State whether the following statementsare True or False. 1. Cuticles are small openings in the bark of young branches. 2. Cuticular transpiration is significant in dry conditions. 3. Maximum amount of transpiration occurs through lenticels. 4. Each stoma is surrounded bytwo quard cells. 5. Main function of stomata is transpiration. 6. In the bell jar experiment, the potted plant is covered with polythene bag to prevent loss of water. 7. The colour of cobalt chloride changes from pink to blue shows transpiration. F 8. Rate of transpiration increases with increase in temperature. 9. Stomataremain closed during day time to prevent water loss. 10. Increase in wind speed decreases transpiration. 11. Transpiration is favoured when humidity is low. 12. Loss of water in liquid form is called guttation. TRANSPORTOF FOOD ANDOTHER 6c0,+6 HaRbaR SUBSTANCES Plants use carbon dioxide and water to prepare Sieve plate glucose and oxygen in the presenceof sunlight (End wall) by the process known as photosynthesis. Once the food is produced in the leaves, it is required Sieve tube to be circulated to the entire plant body so that the glucose can be used by cach cell to obtain Companion cell energy by respiration. Sunlight + Water+Glucose(Carbohydrates) Fig. 1.12 Transport of food through phloem in plants Carbon dioxide +Oxygen Phlocm tissue is made up of different types o cells; two of them are: Write the balanced chenical equation for 1, Sievctubes photosynthesis. 2. Companion cells A continuous column from the leaves to other The glucose is manufactured mainly in the Parts of the plant is formed by the arrangement palisade cells of leaves and then it is passed to of cylindrical cells, called sieve tubes, one above thephloem which carries it to other parts of the the other. It has sieve-like partitions at both ends plant. Transport of food materials from leaves to other parts of theplant iscalled translocation. These partitions are called sieve plates. The The food can be stored in roots, stems or fruits. companion cells are found next to the sieve cells that assist the sieve tubes to function properly. 8  Transpiration of water then rests fo arsNertte the tro qts terin plarts th wee folon The the Companion Source follovig tabie Cell (Leafcell) Water Time of day 3h 9h12h 16 plant A (rnl) Water los in 02 190177 plart B (rl) Sieve tube elernents 1, Frorrm vhich plart was the eaes anont of water loss recoded? 2. V/hich tirme of day wa,the yeAe Ae n -Translocation of sucrose reoes ta bottn plarts A arss 8? Why do y think this s07 IMPORTANCE OF MINERALS Plants nced a nurnber of minerals for healthy Water growth. These are absorbed through the roots Companion Sink cell (Root cell) as rnineral íons dissolved in the soil vwater. b. Phloen la. Xylern The minerals (nutríentelernents) requiíred by Fig. 1.13 Transport of rmaterials in plants through the plants are divided into two categories xylem and phloem rnícronutrients and macronutricnts. Micronutrients are the esential elements that are(A2 INFO HUB required in extremelysmall quantitiesby the planty Applied chernicals, such as pesticides, also /They include boron (B), copper(Cu),iron (Fe), move through the plant by translocation. manganese (Mn), molybdenum (Mo),zinc(Zn), nickel (Ni) and chloride (CIFor cxarnple, the ACTION TIME 2 Aim: To check transportof materials in a presenceof copper is cosely pfoduction, and ít helps ensuresuccessful linked to vitarnin protein A synthesis. Iron (Fe) is essentíal forcrop growth plant. Procedure 1: and food productíon.Manganese (Mn)actívates Cut the flower stalk of a white flower several ímportant metabolic reactions and plays lengthwise. Place each segrnent of stalk in a a direct role in photosynthesis. Zincisa part of different-coloured dye. Predict how the colours plant's enzyrnes. might move up the stalk and into the flower. Leave for a few hours and observe the changes Mácronutrients are he essential elements that Explain the reason for colour change. are required inlarge quantities by the plantsThey Procedure 2: an important role in balanced crop nutrition. The water two plants was recorded over rhey include nitrogen a 12-hour loss in period. Study the inforrmation and (N), phosphorus ). potassiurn (K), calciurn (Ca), sulphur (S), 9  taghesim (Me), NPK salts Are very also involved in numerous cnzyme reasi inysortant fo the plant gwth.For cxample, asan cffective activatof, in which itis closey itrogen is quind or protein formation, associated with encrgy-supplyingphosphon phopho or production of cneggy, and compounds, ngulates the opening and closing potassium Lackofnutrientelementscanlead to deficiencies of stomata. Magnesiun is A constitucnt of (Table 1.1). the chloophvllmolecule. AsA cATier, it is Table 1.1 Deficiencies due to lack of some nutrient elements Micronutrients Iron Yellowing of leaves (chlorosis) Manganese Yellovwing of leves with grey spots (chlorosis) Zinc Maltormed leaves,yellowing of leaves, stunted plant growth Macronutrients Ntrogen Yellowing of leaves, retarded growth, wrinkling of cereal grains PhosphorsDelay in seed germination, poor root growth, purple and red spots on leaves Potassum Poor and stunted growth Quick Check: 4 A.State whether the following statementsare True or False. 1 Phioem transport isbidirectional. 2Gucose srequired by every cell for respiration. 3 Food can be stored only in leaves. 4Pant requires only water for photosynthesis. 5 Sieve tubes assst companion celis 8 Fil in the blanks. (Sievetubes/Stomata) form a continuous columnfrom leaves to other parts of plants 2Gucose is fomed in (patisade'cuticular) cells of leaves 8 Transport of foodfrom leaves to other parts ofleavesis caled (transpiration transiotation) 4 Mioere tissueiSade up of and (sieve tubes/xylem cells comparnion cells) $. Ntiogen isa (micronutrient/macronutrient) for plants 6 The loss of wwater in iquid state is called hydathodes/guttation)