Plant Nutrition IGCSE Biology Revision PDF

BY CELL :00201110983031 00201110983031 [email protected]  1. Outline the subsequent use and storage of the carbohydrates made in photosynthesis, limited to: 2. (a) starch as an energy store 3. (b) cellulose to build cell walls...

BY CELL :00201110983031 00201110983031 [email protected]  1. Outline the subsequent use and storage of the carbohydrates made in photosynthesis, limited to: 2. (a) starch as an energy store 3. (b) cellulose to build cell walls 4. (c) glucose used in respiration to provide energy 5. (d) sucrose for transport in the phloem 6. (e) nectar to attract insects for pollination. 7. Explain the importance of: 8. (a) nitrate ions for making amino acids. 9. (b) magnesium ions for making chlorophyll. 10. Investigate the need for chlorophyll, light and carbon dioxide for photosynthesis, using appropriate controls. 11. Investigate and describe the effects of varying light intensity, carbon dioxide concentration and temperature on the rate of photosynthesis. 12. Investigate and describe the effect of light and dark conditions on gas exchange in an aquatic plant using hydrogen carbonate indicator solution. 13. Identify and explain the limiting factors of photosynthesis in different environmental conditions. 14. State that most leaves have a large surface area and are thin, and explain how these features are adaptations for photosynthesis. 15. Identify in diagrams and images the following (structures in the leaf of a dicotyledonous plant, chloroplasts, cuticle, guard cells and stomata,upper and lower epidermis, palisade mesophyll, CELL :00201110983031 00201110983031 [email protected]  PHOTOSYNTHESIS A process by which plants manufacture carbohydrates from raw materials using energy from light. Intake of raw materials Intake of carbon dioxide: by diffusion through stomata. Intake of water: by osmosis through the root hair cells. Trapping of energy - Chlorophyll traps light energy and converts it to chemical energy. - Chemical energy is used in photosynthetic reactions. Formation of food substance or uses of glucose 1- Glucose is the first substance formed by photosynthesis. 2- Glucose can be converted into starch to be stored. 3- Glucose can be converted into cellulose which is used in formation of cell walls. 4- An amount of glucose is used in production of energy by the process of respiration. CELL :00201110983031 00201110983031 [email protected]  Importance of photosynthesis It is the main source of oxygen which is used for aerobic respiration of all living organisms. It is the main source of food for all living organisms. It is necessary for regulating the concentration of carbon dioxide and oxygen. It is the process which traps energy of the sun which later can be found in the fossil fuels such as coal and petroleum. Second: How leaf is adapted to its function. CELL :00201110983031 00201110983031 [email protected]  LEAF PARTS 1.cuticle 1-waxy material that prevents water evaporation from leaf, (impermeable to water, thus, decreasing transpiration) 2- Protect the inner surface of leaf by preventing the entry of disease causing Organisms ( ex: bacteria/ fungi). 3- Transparent with no chloroplast to allow passage of light to inner layers of leaf. 2.upper 1- Single layer of cells, secreting waxy cuticle epidermis 2-Act as a barrier against bacteria & fungi. 3- Transparent with no chloroplast to allow passage of light to inner layers ofleaf. 3.The A- Contains chloroplasts that contain chlorophyll which traps light palisade energy. layer B- The chloroplasts in the palisade cells are closely packed to absorb as maximum light as possible. C- The chloroplasts in the palisade cells are found close to the cell membrane to obtain water and carbon dioxide easily. D- The palisade cells are elongated to: carry more chloroplasts. allow the movement of the chloroplasts to be able to obtain enough light. E- The palisade cells are perpendicular to the upper epidermis to obtain as maximum light as possible. F- The palisade cells have thin cell walls to facilitate obtaining of water and carbon dioxide. 4. SPONGY A-It contains chloroplasts but the number of chloroplasts in the spongy TISSUE layer is less than that of the palisade layer, therefore it helps in the process of photosynthesis. - It contains air spaces to allow circulation of gases. 5.VASCULAR 1. (XYLEM ) with thick lignified walls to transport water and minerals BUNDLE salts to cells in the leaf 2.(PHLOEM )With thin wall to carry away sucrose and amino acid to the sink. 6. STOMATA Are fine openings found in the epidermis to 1.Allow exchange of gases during photosynthesis and respiration. CELL :00201110983031 00201110983031 [email protected]  2.Allow evaporation of water of transpiration. 3.more stomata in the lower epidermis than that in the upper epidermis because the upper epidermis: Is exposed to accumulation of dust. Is more exposed to agents of evaporation of water as heat and light. Each stoma is surrounded two cells known as guard cells: Photosynthesis process 1- carbon dioxide diffuses through stomata in leaf. 2- water absorbed from soil by roots, moves up to stem through xylem vessels to leaf by Osmosis. 3-Chlorophyll in chloroplast absorbs/traps light energy. Where light energy makes carbon dioxide combine with water (with the help of enzymes) to make glucose (organic compound). Now light energy is converted into chemical energy stored in glucose 4- Oxygen is released as a waste product. CELL :00201110983031 00201110983031 [email protected]  The relationship between photosynthesis and respiration. Dark Bright light Dim light Plant respires only. Rate of photosynthesis is Rate of So, oxygen diffuses into the higher than respiration. Photosynthesis nearly equal leaf and carbon dioxide Carbon dioxide diffuses into to that of to leaf and oxygen out of the Respiration so, no gaseous leaf. exchange as the gases are consumed in their process. This is called Compensation point COMPENSATION POINT no gases are produced from the plant because the oxygen produced due to photosynthesis is equal to that needed for respiration, and the carbon dioxide produced due to respiration is equal to that needed for photosynthesis Conditions necessary for photosynthesis 1- Light 2- Chlorophyll 3- Carbon dioxide 4- Water. 5-suitable temperature which affects activity of enzymes that take part in photosynthesis. factors affecting rate of photosynthesis A- External limiting factors B- Internal limiting factors 1-Light intensity. 1 - Number of stomata 2 -Concentration of carbon dioxide 2- Number of chloroplasts. 3-Temperature 3-Surface area of the leaf LIMITING FACTORS CELL :00201110983031 00201110983031 [email protected] Something present in the environment in such short supply that it restricts life processes. EXAMPLE: In shortage of carbon dioxide concentration, the rate of photosynthesis slows down ,In this case carbon dioxide concentration is considered as a limiting factor. plants need nitrate and magnesium ions ( mineral salts mg+2)? Plants need minerals for healthy growth. They are absorbed through the roots by active transport, as mineral ions dissolved in the soil water. CELL :00201110983031 00201110983031 [email protected]  How to increase the soil fertility 1. Adding artificial fertilizers. 2. Using animal manure. 3. Growing leguminous plants to allow growth of nodular bacteria that makes nitrogen fixation. Mineral Element Importance Deficiency Nitrate ions Nitrogen 1.Needed to make amino acids 1. Decreasing the required to make growth rate that A. proteins as enzymes, cell wall, causes decreasing in membrane. the stem and root B. chlorophyll. leaves size. C. Needed to make nucleic acids 2. Pale or yellow (DNA). plant. Magnesium Mg +2 Needed to make chlorophyll 1- 1. Yellow leaves yellow leaves Which is needed 2. The plant will die for photosynthesis. due to the absence of photosynthesis 4. Allow soil aeration. Eutrophication Reason: Excessive use of fertilisers Excessive fertilisers released into rivers. stimulate growth of algae on the lakes surface. This blocks light from reaching plants below the surface, so no photosynthesis. CELL :00201110983031 00201110983031 [email protected] Plants die. Aerobic Bacteria decompose dead plants using 02 dissolved in water t The oxygen concentration in water decreased ( lack of 02) in water causes death of aquatic living organisms. CELL :00201110983031 00201110983031 [email protected]  PRACTICAL WORK Common procedure Destarching Means the removal of the stored starch in a plant - It takes place by placing the plant in a dark place for about 48 hours to consume all its stored starch in carrying out its metabolic activities without building new food due to absence of light. How to test the presence of starch in the plant leaf Procedures 1- Put the leaf in boiling water for about 30 minutes to: a- denature the enzymes and to prevent any further chemical changes. b- make the cell more permeable to iodine solution. 2- Put the leaf in boiling alcohol using a water bath: - to dissolve the chlorophyll, to be able to observe the change in colour after adding iodine solution clearly. (water bath is used because alcohol is flammable) 3- Put the leaf in hot water to soften it because alcohol makes it brittle. 4- Put the leaf in a Petri dish, and add iodine solution: CELL :00201110983031 00201110983031 [email protected] Observation and conclusion - if the colour remains yellow brown this means that starch is absent. - if the colour changes to dark blue (blue black), this means that starch is present. Investigation the necessity of the limiting factors 2.chlorophyll is necessary for photosynthesis Procedures 1- Get a plant of variegated leaves. (variegated leaves means leaves with parts containing chlorophyll while the other parts are free from chlorophyll) 1- Destarch this plant by placing it in a dark place for about 48 hours. 3- Expose the plant to light for suitable period of time. 4- Take one of its leaves ,and draw it carefully to show where chlorophyll is found. 5- Test for starch in this leaf Observation The parts were previously green turn blue black. - The other parts gain the yellow brown colour of iodine solution. Conclusion - Chlorophyll is necessary for photosynthesis. CELL :00201110983031 00201110983031 [email protected]  2.light is necessary for photosynthesis Procedures 1- Get a potted plant, and destarch it. 2- Cover a part of one of its leaves with aluminum foil as shown in figure. 3- Let the plant exposed to light for about three hours. 4- Test the leaf for starch using iodine solution. Observation: The covered parts gain the yellow- brown colour of iodine solution. - The parts exposed to light gain dark blue color. Conclusion Light is necessary for photosynthesis CELL :00201110983031 00201110983031 [email protected]  2.carbon dioxide is necessary for photosynthesis Procedures 1- Get a potted plant and destarch it by being placed in a dark place for about 48 hours. 2- Put one of its leaves in a flask containing soda lime, potassium hydroxide or sodium hydroxide solution to absorb carbon dioxide. 3- Put other leaf in another flask containing distilled water (to be used as a control experiment.) 4- Expose the plant to light for a suitable period of time. 5- Take the two leaves and test for starch Observation: No starch can be detected in the leaf which is found in the flask that contains potassium hydroxide. (The colour of iodine solution remains yellow brown.) - Starch can be detected in the leaf which is found in the flask that contains distilled water. (The colour of iodine solution becomes blue black) Conclusion - Carbon dioxide is necessary for photosynthesis. CELL :00201110983031 00201110983031 [email protected]  proving that oxygen evolves during photosynthesis Procedures 1.Prepare two apparatuses as in fig. (hydrogen carbonate or bicarbonate is used as a source of carbon dioxide as it decomposes releasing carbon dioxide ) 2.Leave one of them exposed to light. 3. keep the other one in a dark place (to be used as a control experiment). Observation: Bubbles of a gas evolve in the apparatus which is placed in light. (Test for this gas using a glowing splint, you observe that it relights.) Conclusion Oxygen evolves during photosynthesis. CELL :00201110983031 00201110983031 [email protected]  2.the effect of light on photosynthesis Procedures In a dark place or in dim light put a light source (e.g. electric lamp) in front of plant. increase the distance between the plant and the lamp record the number of bubbles. Decrease the distance between the plant and the lamp (to increase intensity of light.) and record the number of bubbles. Precaution 1.In this case a HEAT FILTER is used because the lamp produces heat and light, and we need to investigate the effect of light intensity only. The heat filter may be a vessel containing water, that absorbs heat and allows light to pass through it. 2.the investigation is carried out in dark room to prevent the effect of any excess light. Conclusion 1.increasing the distance between the plant and the lamp increase the number of bubbles so, the photosynthesis rate increases. decreasing the distance between the plant and the lamp decreases the number of bubbles so, the photosynthesis rate decreases CELL :00201110983031 00201110983031 [email protected] CELL :00201110983031 00201110983031 [email protected]  How to know which is a limiting factor at a certain point? Increase this factor, if rate of photosynthesis increases, you conclude that this factor acts as a limiting factor at this point. Examples: a- Temperature is a limiting factor at a certain point. Remove the heat filter, as a result of this temperature increases, if rate of production of bubbles increases you conclude that temperature acts as a limiting factor at this point. b- Carbon dioxide is a limiting factor at a certain point. Increase the concentration of carbon dioxide by adding sodium hydrogen carbonate, which decomposes releasing carbon dioxide that dissolves in water. If rate of production of bubbles increases you conclude that carbon dioxide acts as a limiting factor at this point. Why Measuring the rate of photosynthesis by measuring number of bubbles is in accurate 1.the number of bubbles are not of the same size. 2.the bubbles are produced quickly so we can’t count the bubbles produced. 3.some bubbles are too small to be seen. Improvement (by measuring the volume of the oxygen by using syringe or graduated cylinder.) CELL :00201110983031 00201110983031 [email protected]