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Review Question • Which mode of nutrition do the green plants carry out? A. Autotrophic nutrition B. Heterotrophic nutrition Sorry! You’re wrong! • Heterotrophic nutrition is the mode of nutrition in which organisms have to depend on other organisms or dead organic matters as their food sources. Green plants, however, can make organic food by themselves using simple inorganic substances. Back Very Good! • Autotrophic nutrition is the mode of nutrition in which organisms can make organic food by themselves using simple inorganic substances. • The process by which the green plants obtain nutrients is called :- Photosynthesis Overview of nutrition in green plants carbon dioxide and water photosynthesis carbohydrates (e.g. glucose) fatty acids glycerol mineral salts (e.g. NO3-, SO42-) amino acids water nutrients for plants can be used to produce all plant materials (e.g. enzymes, cell wall, cytoplasm, cell membrane, chlorophyll) Nature of photosynthesis • Anabolic process • Takes place in chloroplast • Necessary factors : •Carbon dioxide •Water •Sunlight •Chlorophyll Light Light Absorption Spectrum Why leave looked green? Different pigments in absorption spectrum How light energy used? Light reaction • Light energy is trapped by chlorophyll in chloroplast Light reaction Light energy absorbed by chlorophyll splits water molecules into hydrogen and oxygen Light reaction Oxygen is released as a gas through stoma to outside Light reaction Hydrogen is fed into dark reaction Dark reaction Water Hydrogen formed produced a in by-product light reaction combines witheither CO2 toin form • Noislight isasrequired; can take place carbohydrates light or darkness Chlorophyll Structure Light Reaction Photophosphorylation Cyclic photophosphorylation Dark Reaction M. Calvin Calvin Cycle CHLOROPLAST Fate of product of photosynthesis Kreb cycle Factors affect rate of photosynthesis Expt. Show effect of factors Conc. Of Distance NaHCO3 Heat Fate of carbohydrate products in the plant carbon dioxide and water photosynthesis carbohydrates (e.g. glucose) fatty acids glycerol mineral salts (e.g. NO3-, SO42-) amino acids water Fate of carbohydrate products in the plant carbon dioxide and water photosynthesis mineral salts (e.g. NO3-, SO42-) carbohydrates (e.g. glucose) fatty acids glycerol amino acids release energy by respiration water Fate of carbohydrate products in the plant carbon dioxide and water photosynthesis mineral salts (e.g. NO3-, SO42-) carbohydrates (e.g. glucose) fatty acids glycerol amino acids convert into starch for storage water Fate of carbohydrate products in the plant carbon dioxide and water photosynthesis carbohydrates (e.g. glucose) fatty acids glycerol mineral salts (e.g. NO3-, SO42-) amino acids change into sucrose and is transported to other parts through phloem water Fate of carbohydrate products in the plant carbon dioxide and water photosynthesis carbohydrates (e.g. glucose) fatty acids glycerol mineral salts (e.g. NO3-, SO42-) amino acids combine to form fats and oils to form cell membranes and as a food store water Fate of carbohydrate products in the plant carbon dioxide and water photosynthesis carbohydrates (e.g. glucose) fatty acids glycerol mineral salts (e.g. NO3-, SO42-) amino acids water join together to become protein molecules Mineral requirements in plants • In order to synthesize amino acids, nitrate ions must be taken into the plant from the soil through the root • Other minerals are also necessary to maintain the life of the plant Expt. Show effect of minerals Different Nutrient added The importance of nitrogen • For synthesis of proteins, chlorophyll, etc. • Taken in the form of nitrate ions • Deficiency symptoms: – Little growth (no protein made) – Yellowing of leaves (chlorophyll made) The importance of magnesium • Essential component of chlorophyll • Deficiency symptoms: – Yellowing of leaves (no chlorophyll made) – Poor growth (no food manufactured because of lack of chlorophyll) Use of fertilizers in agriculture • Continuous harvesting crops removes the valuable mineral salts from soil Fertilizers are added to replace such loss • Two kinds of fertilizers: – Natural fertilizers – Chemical fertilizers Natural fertilizers • From manure • Organic compounds in it are decomposed by bacteria in soil to form mineral salts Chemical fertilizers • Mainly nitrogenous and phosphorous compounds manufactured artificially Comparison between natural and chemical fertilizers Natural fertilizers Chemical fertilizers Very cheap More expensive Contain humus which can improve soil texture No humus so cannot improve soil texture Less soluble in water so less likely to be washed away Very soluble in water so more likely to be washed away Comparison between natural and chemical fertilizers Natural fertilizers Chemical fertilizers Less soluble in water so more difficult to be absorbed Very soluble in water so easier to be absorbed Time is needed for the decomposition to complete before nutrient is available to plants More readily to be used by the plants Importance of photosynthesis • It is the only method to convert energy in sunlight into chemical energy – Animals have to depend on plants for food supply – Plants: producers; animals : consumers • To maintain a constant oxygen level in the atmosphere Experiments to test for necessary factors of photosynthesis • Experimental set-up: To remove the factor under study and to see if photosynthesis still takes place • Control set-up: Identical to experimental set-up except that the missing factor is present A set-up to study whether light is necessary for photosynthesis Region B Region A water leafy shoot Which is the control, the exposed region A or the shaded region B? What is the purpose of setting up region A? • As a control Too simple and not explicit! To show that photosynthesis cannot take place in the absence of light Destarching • Reason: – To avoid any existing starch in the leaves interfering with the result, and to show that any starch found after the experiment was produced during the period of investigation • Method: – By placing the plant in dark for at least 24 hours Parts of plant where photosynthesis takes place • Places where chloroplasts are found • Mainly in the leaf because – it contains a lot of chloroplasts – it is well adapted for performing photosynthesis Cross-section of a dicot leaf upper epidermis protect internal tissues from mechanical damage and bacterial and fungal invasion Cross-section of a dicot leaf Cuticle • a waxy layer • prevent water loss from the leaf surface Cross-section of a dicot leaf mesophyll Cross-section of a dicot leaf palisade mesophyll columnarmany cells contains closely packed chloroplasts together absorb light more efficiently Cross-section of a dicot leaf irregular cells loosely packed together to leave numerous large air spaces allow rapid diffusion of gases less chloroplasts throughout the for leaf photosynthesis spongy mesophyll Cross-section of a dicot leaf same as upper epidermis except the cuticle is thinner lower epidermis Cross-section of a dicot leaf stoma opening which allows gases to pass through it to go into or out of the leaf Cross-section of a dicot leaf guard cells control the size of stoma Cross-section of a dicot leaf vascular bundle (vein) Cross-section of a dicot leaf xylem •to transport water and mineral salts towards the leaf Cross-section of a dicot leaf phloem •to transport organic substances away from the leaf Adaptation of leaf to photosynthesis Upper epidermis and cuticle is transparent Allows most light to pass to photosynthetic mesophyll tissues Adaptation of leaf to photosynthesis Palisade mesophyll cells are closely packed and contain many chloroplasts To carry out photosynthesis more efficiently Adaptation of leaf to photosynthesis Spongy mesophyll cells are loosely packed with numerous large air spaces To allow rapid diffusion of gases throughout the leaf Adaptation of leaf to photosynthesis Numerous stomata on lower epidermis To allow rapid gaseous exchange with the atmosphere Adaptation of leaf to photosynthesis Extensive vein system • Allow sufficient water to reach the cells in the leaf • To carry food away from them to other parts of the plant CHEMOSYNTHSIS •Iron bacteria •Colorless sulphur bacteria •Nitrifying bacteria Iron bacteria Nitrifying bacteria