Transport In Plants IGCSE Biology Past Paper PDF 2024

BY CELL :00201110983031 00201110983031 [email protected]  1. 1 State the functions of xylem and phloem: 2. (a) xylem – transport of water and mineral ions, and support 3. (b) phloem – transport of sucrose and amino acids 4. Identify i...

BY CELL :00201110983031 00201110983031 [email protected]  1. 1 State the functions of xylem and phloem: 2. (a) xylem – transport of water and mineral ions, and support 3. (b) phloem – transport of sucrose and amino acids 4. Identify in diagrams and images the position of xylem and phloem as seen in sections of roots, stems and leaves of non-woody dicotyledonous plants. 5. Identify in diagrams and images root hair cells and state their functions 6. State that the large surface area of root hairs 7. increases the uptake of water and mineral ions 8. Outline the pathway taken by water through the root, stem and leaf as: root hair cells, root cortex, cells, xylem, mesophyll cells. 9. Investigate, using a suitable stain, the pathway of water through the above-ground parts of a plant. 10. Explain the significance of villi and microvilli in increasing the internal surface area of the small intestine. 11. Describe the structure of a villus. 12. Describe the roles of capillaries and lacteals in villi. 13. Relate the structure of xylem vessels to their function, limited to: 14. (a) thick walls with lignin (details of lignification are not required) 15. (b) no cell contents 16. (c) cells joined end to end with no cross walls to form a long continuous tube CELL :00201110983031 00201110983031 [email protected]  Importance of water to plants: 1. Keep the cell turgid and this is necessary for support 2. Used in photosynthesis 3. Forms part of the cytoplasm, vacuole, and cell organelles. 4. Water transpired helps in: a. Ascent of water and minerals from root b. Cools down the plant during hot days. HOW THE WATER IS UPTAKEN INTO THE PLANT 1. By osmosis - The water potential (concentration of water) in the soil is higher than that inside the root hair cells. - The cell membrane of the root hair cell is partially permeable. - Therefore, water enters the root hair cells by osmosis. 2. Soaking - An amount of water is soaked by the cell wall, and passes through it from one cell to another. CELL :00201110983031 00201110983031 [email protected]  The passage of water through (across) the root An amount of water passes through the cytoplasm from the epidermal cells to the cortex cells to the endodermis to enter the xylem vessels. (This movement is carried out by osmosis due to the difference in water concentration among the cells.) 2. An amount of water is soaked by cellulose cell walls, it moves from a cell wall to another How Water ascends through xylem? by many forces: a. The main force is the transpiration force. b. The root pressure due to the turgidity of the root cells. c. The capillary action as the xylem vessels are very narrow therefore they act as the capillary tubes. The pathway of water through a stem 1. From the xylem of the root water moves through xylem of the stem. 2. The movement of water through xylem of the stem depends mainly on the pull force created by the process of transportation. 3. Water is then transported from xylem of the stem to the xylem of the leaf. CELL :00201110983031 00201110983031 [email protected]  Vascular bundle FUNCTION ADAPTATION XYLEM 1-Transport water and 1-They are made of dead dissolved mineral ions from cells, with no nucleus and no root up the stem to leaves. cytoplasm so water& mineral ions can pass freely. 2-No end walls so that many cells form a continuous tube. 3-They run from roots right up through stem to leaves 2-support the stem 1-They have thick cell wall containing lignin which is waterproof and help resist strains by wind. PHLOEM 1-Translocate(transport) 1-Formed of sieve tubes sucrose and amino acids which has thin layer of dissolved in sap solution Cytoplasm ( as the cell must from region of production to stay alive or else sugar region of storage or transport utilisation (respiration & will stop) but no nucleus or growth) organelles so sugar flow is not impeded. 2-Pores in sieve plates through which sugar pass from one cell to next. 3-Companion cell doesn't transport sugar but carryout some life processes of sieve tubes. CELL :00201110983031 00201110983031 [email protected] Water movement through a plant begins with diffusion of water vapour out of the leaf and evaporation from the leaf surface (spongy mesophyll). 98% of water taken up by a plant is lost to the atmosphere by transpiration to help cool down the plant in hot weather. Transpiration loss of water from plant leaf By evaporation of water at the surface of spongy mesophyll cells, Followed by diffusion of water vapour through stomata, down concentration gradient. CELL :00201110983031 00201110983031 [email protected]  Factors that affect transpiration External factors (The factors related to the surrounding environment) 1. Air current The increase in movement of air causes an increase in the rate of transpiration because air carries water molecules away from the leaf causing the surrounding air to become less saturated than the air inside the air chambers inside the leaf, therefore water vapor flows outside the leaf. 2. Temperature The increase in temperature increases the rate of transpiration due to increasing the rate of kinetic energy gained by the water. 3. Light Increasing the light intensity Increases the rate of transpiration because in presence of light stomata open for obtaining a carbon dioxide for photosynthesis (directly proportional) 4. Humidity Increase humidity decreases the rate of transpiration (inversely proportional) (Therefore, if a plan is placed in a plastic bag rate of transpiration continues high until air inside becomes more humid than it begins to decrease, other factor responsible for this decrease is that it is protected the effect of air currents) Internal Factors: (Are the factors related to the structure of the plant) 1. Number of stomata Increase in number of stomata increases the rate of transpiration. 2. Air spaces in the leaf - Increase in air spaces increases the rate of transpiration. 3. The exposed surface area - Increase in the exposed surface area increases the rate of transpiration. 4. Thickness of cuticle - Increase in thickness of cuticle decreases the rate of transpiration. CELL :00201110983031 00201110983031 [email protected] The plant needs water for 1-prevent wilting and maintain cell turgidity. wilting might happen due to : 2- Transport of minerals. 3- medium for enzymatic activity. 4 -raw material for photosynthesis. Practical INVESTIGATION OF TRANSPIRATION Investigate which part of the stem transport water and solute The device used: potometer Steps Observation and conclusion  Cut a shoot of a plant and pill in coloured 1.the xylem part of stem contained the dye, water. indicates that xylem transport water.  Leave It for few minutes.  Cut a very thin cross section in the stem  Put the section in a drop of water on a microscopic slide.  Cover It with coverslip.  Observe under the microscope INVESTIGATE THAT THE PLANT LOSES WATER VAPOUR BY TRANSPIRATION Steps Conclusion  Using two similar well-watered potted  The plant with bag covering It will lose plants. less weight than the exposed one.  Enclose the first entirely polyethene bag  This Is because in the exposed plant including its pot as a control water vapour Is lost to the environment  Enclose the pot of the second with from Its leaves by transpiration. polyethene bag.  While in other plant water vapour  place both plants on balance and record remains trapped inside the bag their measures.  record the mass of each plant everyday at the same time for at least 1 week. CELL :00201110983031 00201110983031 [email protected]  POTOMETER It is an apparatus used to measure the rate of water uptake. - It cannot be used to measure the rate of transportation because not all the water taken by the plant is transpired 1- part used as a raw material for photosynthesis. 2- part needed for turgidity and support. 3- part needed for transport of solutes( food substances) 4- part takes part in chemical reactions( hydrolysis& breaking down of food substances. 5- medium for chemical and enzymatic reactions - Potometer can be used to detect transpiration, (or to indicate) but not to measure the rate of transpiration. How does potometer is used ? - When water is lost from the plant, it begins to absorb water from the apparatus, as a result of this absorption water moves along the scale. - The distance moved by water along the scale represents the amount of water taken by the Plant. Explain the potometer has to be assembled under water. - To avoid the presence of any air bubbles which when enter the xylem it cause its blockage (or cause breaking down) of the water column) leading to resistance in the ascent of water. Explain The leafy shoot has to be dried before starting the experiment. - Because the presence of water on the leaves decreases or even stops transpiration until all CELL :00201110983031 00201110983031 [email protected] What are precautions required to transfer a plant from one soil to another 1. Keep part of the soil surrounding the root. 2. Keep this part of soil moist (try to know why). 3. Cover the plant with a waterproof bag. Potometer can be used to detect the effect of light on the transpiration rate. Put between the potometer and the lamp a heat filter to avoid the effect of the heat produced by the lamp on the rate of transpiration. Wilting Wilting means that a plant loses water to the extent that the cells of its leaves become flaccid. Causes of wilting 1. When the rate of transpiration is higher than the rate of water uptake. (in presence of hot weather or strong wind) 2. When the conc. Of water in the cell sap is higher than the surrounding medium. Example: presence of the plant in salty soil, or when sea water reaches the soil. Mechanism of movement of water in the plant 1. Transpiration force:  Transpiration produces a tension pull from the above creating a water potential gradient in  xylem, drawing water molecules up the plant.  The loss of water from the leaves reduces the water potential at the top of the xylem, and CELL :00201110983031 00201110983031 [email protected]  this creates a water potential gradient along the plant, as a result the potential of water at the base of the plant becomes higher than above, this causes the water to ascend in the plant.  This is the main force used for ascent of water and minerals.  The plant transpires about 98% of the water it absorbs. 2. Root pressure. 3. Capillary. Translocation Is the transport of sucrose and amino acids, dissolved in sap solution to move through phloem by active transport/ Diffusion, from region of production or absorption(source)....... to regions of utilization in respiration and growth (ex: buds, small leaves, flowers) or to regions of storage as roots or stem (sink). Xylem Phloem  Transport water and Minerals.  Transport manufactured food in the  Has lignified walls. form of sucrose and amino acids.  Consists of fine tubes called xylem  No lignified walls vessels.  Consists of sieve tubes and companion cells.  Contains no cytoplasm.  Lined with cytoplasm  Contains no nucleus.  Companion cells contain nucleus  Has no transverse walls.  The transverse walls are perforated  Considered as dead tissue.  Living tissue.  Cannot carry out active transport.  Translocated food active transport. CELL :00201110983031 00201110983031 [email protected]  Sink Source regions of utilization in respiration and region of production or absorption growth EX -Roots in normal conditions Ex :Leaves. IN WINTER/AUTUMN/SPRING IN SUMMER ROOTS ARE A SOURCE LEAVES ARE A SOURCE There is fewer leaves. So less photosynthesis. There is more sunlight for photosynthesis So light is a limiting factor. And starch is broken into sucrose. To be translocated through phloem to different parts of plant that need energy for growth for forming new shoot & leaves. GROWING LEAVES: SINK ROOTS ARE SINKS Use sugar in respiration to release energy The starch is changed into glucose to be for growth. used in respiration. CELL :00201110983031 00201110983031 [email protected]  Transport Translocation It is the movement of water and minerals It is the movement of sucrose and inside plants. amino acids from region of production - Takes place in xylem. or absorption to regions of utilization. - Takes place down upwards. - Takes place in phloem - It is a physical process, does not need - Takes place in all directions Energy. - It is a biological process needs energy The plant adaptation Aquatic plants (hydrophytes) Roots Stem Leaves 1. Roots do not attach to Elastic : 1. Large air spaces the bed of river or pond In order not to be For buoyancy and floating of plant and So as not to cut by broken down by the to allow gas diffusion. water current. effect of water 2. Thin cuticle: current As no need to reduce water loss. - Contain air spaces to 3. Little thin lignin in xylem , since the keep the plant float leaf is supported by water. near the water surface 4. Leaves are :floating on water for photosynthesis. surface.: For efficient absorption of light. " 5. Stomata found on upper surface of leaf: To allow diffusion of gases from air and prevent entry of water. CELL :00201110983031 00201110983031 [email protected]  Root Stem Leaves 1. Deep 1. Has upright shape which 1.very small in the form of To be extended to high reduces surface area for spines depth in the soil to absorb heat absorption.  to decrease the water more water. 2.succelent to store more loss 2. Branched: water  in order not to be To increase surface area for 3. green a sit contains ruptured by wind absorption. chlorophyll to carry out  to protect the plant photosynthesis against being eaten. 2.fewer stomata to decrease the water loss. 3. hairs on the to decrease the air flow and increase the humidity. CELL :00201110983031 00201110983031 [email protected]