Plant Respiration .pdf

Downloaded from https:// www.studiestoday.com 7 RESPIRATION IN PLANTS Syllabus : Respiration in plants : outline of the process, gaseous exchange. A brief outline of the process mentioning the terms Glycolysis and Krebs cycle and their significance. A r...

Downloaded from https:// www.studiestoday.com 7 RESPIRATION IN PLANTS Syllabus : Respiration in plants : outline of the process, gaseous exchange. A brief outline of the process mentioning the terms Glycolysis and Krebs cycle and their significance. A reference to be made to aerobic and anaerobic respiration with chemical equations in each case. Experiments on gaseous exchange and on heat production. Like all other organisms, plants too require energy When energy in the form of ATP is used, for carrying out body activities. In this chapter you the ATP is converted to ADP (adenosine diphosphate) will learn about the two kinds of respiration (aerobic and again when more energy is available by further and anaerobic), the manner in which diffusion of breakdown of glucose, the ADP is reconverted to ATP respiratory gases occurs, as well as a number of and so it goes on and on (Fig. 7.1). One mole of glucose interesting experiments to demonstrate respiration in on complete oxidation yields 38 molecules of ATP. plants. BREAKDOWN OF FOOD (GLUCOSE) IN RESPIRATION СОг 7.1 WHAT IS RESPIRATION? ENERGY H20 All living cells in a plant, as well as those in animals, require energy for various body activities. For example, building up proteins from amino acids, HEAT making starch from glucose, absorbing minerals from the soil, or the laying down of cell walls by the plant PHOSPHATE cell, are all such activities that require energy. This ADP ATP energy is made available by the breakdown of glucose PHOSPHATE a simple carbohydrate. This chemical breakdown occurs by utilizing oxygen and is represented by the following overall reaction : CH,20 + 602 → 6C02 + 6H,0 + energy ENERGY USED IN WORK There are three important characteristics of Fig. 7.1 Diagrammatic representation to show the use respiration in this equation. of energy liberated in respiration 1. The breakdown of glucose (CH,2%%) to carbon dioxide and water does not occur in a single step, ATP - The energy currency of the cell All activities inside a living cell need energy which but in a series of chemical steps. These steps is available in the form of ATP as the immediate occur in two major phases- i) glycolysis (glucose source. Hence, this chemical compound ATP is → pyruvate) occurring in cytoplasm and ii) Krebs described as "The energy currency of the cell". cycle (pyruvate → CO2 + 6H,0 + ATP) occurring Respiration is a catabolic process of releasing energy in mitochondria. from simple sugar glucose for carrying out life processes. 2. Each breakdown step is due to a particular Living organisms show two types of metabolic enzyme. activities : 3. The energy liberated in the breakdown of the (i) anabolic (constructive or biosynthetic processes), glucose molecule is not all in the form of heat, but it consumes energy. a large part of it is converted into chemical energy (ii) catabolic (destructive or breaking down in the form of ATP - a chemical substance called processes), it gives out energy for use by the adenosine triphosphate. organism. 50 Downloaded from https:// www.studiestoday.com  Downloaded from https:// www.studiestoday.com Respiration is a breaking down process by which actually, there is more carbon dioxide inside our a living cell oxidises organic substances (glucose) houses than under a tree at night). Sleeping under a and releases carbon dioxide, water and energy. tree during hot mid-day is definitely good as one gets both oxygen due to photosynthesis and coolness 7.2 RESPIRATION vs. BURNING (Combustion) due to transpiration. Sometimes, respiration is compared with burning such as the burning of coal. Both liberate energy, and PROGRESS CHECK both give the end products CO, and water. But this What are the three important aspects about the overall comparison is only superficial. The differences between chemical equation of respiration, pertaining to the the two are as follows : following? Respiration Burning/Combustion (i) Single or several steps 1. Occurs in a series Occurs in a single step (ii) Direct or enzyme-catalysed of chemical steps 2. Carried out by enzymes Carried out by heat (iti) Forms of energy liberated 3. Biochemical process Physico-chemical process 4. Energy liberated as All the energy liberated as heat 2. List three ways in which respiration is different from ATP and some heat and light. 5. No light energy is burning : Light is produced produced (i) 6. Cellular process Non-cellular process (ii) 7. Occurs at body Occurs at high temperature (iti) temperature (at ignition point) 3. Name the three inlets of oxygen for respiration in 7.3 THE ENTIRE PLANT RESPIRES plants. Every part of a plant such as the leaves, stem, (i) roots and even the deepest placed cell in any region (ii) respires. Oxygen is obtained from the atmosphere (iin) through three inlets : > stomata in leaves 7.4 TWO KINDS OF RESPIRATION - AEROBIC > lenticels in stem AND ANAEROBIC > general surface of the roots A. AEROBIC RESPIRATION Normally, free oxygen is used in respiration and Ploughing or tilling of the soil creates tiny air there is complete oxidation of glucose with the spaces around soil particles and provides the source formation of carbon dioxide and water as end- of oxygen for the roots. Water-logged and compact products. This is clearly represented by the following soil does not have air spaces which affect respiration overall reaction (actually there are numerous steps in of the roots. the entire process) : During daytime, due to photosynthesis, the leaves C,H,20 + 602 → 6C02 + 6Н,0 + 38 АТР produce oxygen, some of which is used in respiration (energy/heat) and the rest is diffused out. The carbon dioxide Respiration proceeds only when oxygen (a produced during respiration in the leaves serves as a constituent of air) is available and is therefore called raw material for photosynthesis. aerobic (or oxybiotic) respiration. At night, even the leaves obtain oxygen from the atmosphere and give out carbon dioxide. Hence, B. ANAEROBIC RESPIRATION there appears to be some truth in the belief that Sometimes certain parts of the plants including one should not sleep under a tree at night (also fruit and seeds) may temporarily respire even in the see the box at the end of this chapter page 62). (But absence of oxygen. In this type of respiration, the 51 Downloaded from https:// www.studiestoday.com  Downloaded from https://www.studiestoday.com glucose molecule is incompletely broken down into ethanol (ethyl alcohol) and carbon dioxide with the SODA SODA release of a small quantity of energy. This chemical LIME LIME DEAD reaction can be represented in the following manner : B BEANS cam: С,Н,20% → 2C,H,OH + 2C0, + 2 АТР GERMINATING BEANS 020.01 Glucose Ethanol WET COTTONWOOL WET COTTONWOOL AND ANTISEPTIC This type of respiration is called anaerobic respiration (or anoxybiotic) as it proceeds even without oxygen. Anaerobic respiration in any part cannot continue in a plant for more than a few days and the part ultimately dies. But there are certain microscopic organisms such as certain bacteria and fungi which normally respire only anaerobically. Even the germinating seeds when deprived of air respire anaerobically as described in Experiment Fig. 7.2 Experiment to show the utilisation No. 5 Fig 7.7(p. 54). of oxygen in respiration. Table 7.1Major differences between aerobic and (A) contains germinating bean seeds and Flask (B) has anaerobic respiration in plants dead (boiled) seeds together with some antiseptic to avoid Aerobic respiration Anaerobic respiration bacterial decay. Wet cotton provides water to both 1. Proceeds in the Proceeds in the absence samples. A small tube containing soda lime (a mixture of presence of oxygen. of oxygen. sodium hydroxide and slaked lime) is suspended in each 2. Complete break- Incomplete breakdown flask for absorbing any carbon dioxide released by the down of glucose. of glucose. seeds. After a few days, the delivery tube connected with 3. End-products are End-products are ethyl flask (A) will show a greater rise in water level. When a carbon dioxide alcohol and carbon burning paper is introduced into each flask after removing and water. dioxide. their corks, the flame is immediately put off in flask (A). 4. Energy liberated Energy liberated in but it continues for a short while in flask (B). This proves in large quantity small quantity (2 ATP) that oxygen was absent in flask (A) showing thereby that (38 ATP) from one from one mole of it was used up by the germinating seeds and the volume mole of glucose. glucose. of oxygen so used up was indicated by the rise of water 5. Occurs normally Occurs temporarily for level in the delivery tube. There are two simple questions throughout life. short periods. which surely you can answer. Why is there a slight increase in the level of water in the delivery tube of flask PROGRESS CHECK (B)? Which of the two flasks, (A) or (B), is a control? 1. Give the overall chemical equation for the two kinds of respiration in plants : A Proper Experiment Must Have (i) Aerobic Two Components : (i1) Anaerobic EXPERIMENTAL and CONTROL 2. Mention any one difference other than those reflected An experiment consists of two set-ups - an in the two chemical equations given above. experimental set-up and a control set-up. Both are identical in which every condition is the same 3. Certain organisms respire only anaerobically throughout their lives. Name any two such organisms. except one. The set-up in which the condition (i) under study is missing is called the control. (ii) 7.5 EXPERIMENTS ON RESPIRATION IN PLANTS 2. Experiment to prove that carbon dioxide is produced 1. Experiment to prove that oxygen is used up in during respiration in germinating seeds. respiration. Take two flasks A and B. Place some wet cotton-wool An apparatus is arranged as shown in Fig. 8.2. Flask at the bottom of each flask. Soaked seeds (such as pea or 52 Downloaded from https:// www.studiestoday.com  Downloaded from https:// www.studiestoday.com An alternative method for the same experiment A similar more directly observable experiment to show that carbon dioxide is produced during respiration in germinating seeds (pea or gram seeds) is arranged as shown in Fig. 7.4. The air drawn in conical flask A is cleared of SOAKED BOILED any CO, present in it. The clear limewater in flask B BEANS BEANS confirms that the air entering flask C is CO, free. The limewater in flask D turning milky doubtless proves that WET COTTONWOOL the source of CO, was only the germinating seeds. 3. Experiment to prove that carbon dioxide is produced by green plants during respiration. Set up an apparatus as shown in (Fig. 7.5) using a small TESTING FOR CO2 potted plant such as Geranium. The bell-jar should be placed on a glass sheet and its rim as well as all other connections should be vaselined to make them air-tight. The outside air is drawn into the apparatus with the help LIMEWATER of an air pump. This air passes through the soda-lime which Fig. 7.3 Experiment to show the production of absorbs any carbon dioxide present in the incoming air, carbon dioxide in germinating seeds. and the limewater (Flask A) through which it passes will not turn milky. As the air leaves the bell-jar, and passes bean) are placed in flask (A) and an equal number of boiled through another sample of limewater (Flask B), the carbon (dead) seeds are placed in flask (B) (Fig. 7.3). dioxide present in it would turn the limewater milky. It is A little antiseptic (such as carbolic acid) is added to flask (B) to prevent bacterial growth on dead seeds, which AIR would otherwise respire and release carbon dioxide. The CO2 FREE AIR AIR flasks are securely corked and left in similar conditions of AIR light and temperature. A few days later, the seeds in flask SUCTION (A) will be found to have clearly germinated and those in PUMP flask (B) showing no signs of any germination (as they are dead). The gases in each flask are then tested by removing SODA LIME the cork and tilting the flask over a test-tube containing limewater and then shaking up the test-tube. The expected gas carbon dioxide being heavier than air would "flow B down" into the test-tube. The gas from flask (A) would 2298 turn the lime- water milky, showing the presence of carbon LIMEWATER LIMEWATER dioxide in it, while the gas in flask (B) will show no effect. (Turns milky) (Clear) Therefore, the conclusion is that the germinating (respiring) Fig. 7.5 Experiment to show that carbon dioxide seeds give out carbon dixoide. is given out by a green plant in the dark. AIR TO AIR SUCTION PUMP B C D TWO-HOLE BENT RUBBER LIMEWATER GLASS TURNS MILKY STOPPER TUBES KOH SOLUTION LIMEWATER GERMINATING SEEDS (Dissolves any CO, present in air) Fig. 7.4 To show that carbon dioxide is given off from living plant material during respiration. Downloaded from https://www.studiestoday.com  Downloaded from https:// www.studiestoday.com necessary that this experiment is carried out in the dark, CO or the bell-jar is completely covered by a piece of black cloth to prevent photosynthesis (so that the carbon dioxide GERMINATING SEEDS liberated in respiration is not used up in the synthesis of starch). 4. Experiment to show that heat is evolved during MERCURY respiration (Fig. 7.6). Take two thermos-flasks and mark them (A) and (B). Take about 200 seeds (pea or bean) and soak them in water for more than 24 hours. AFTER THERMOMETER 2-3 DAYS Fig. 7.7 Experiment to demonstrate anaerobic respiration. WET COTTONWOOL carbon dioxide. Carbon dioxide can be tested by introducing a stick of potassium hydroxide into the test- tube, which will float up through mercury and on coming into contact with the gas, will absorb the carbon dioxide and the level of mercury will again rise. A similar control experiment could be set up in which the seeds may be kept after killing them by heating and sterilizing them with some antiseptic. No gas will be liberated in the control. /Note : Peeling off the seed coat of the germinating seeds before introducing them into the test-tube may hasten the outward diffusion of CO,/ B PROGRESS CHECK (Experiment) (Control) 1. In experiments on respiration, the seeds taken as Fig. 7.6 Experiment to show liberation of control are boiled. Why ? heat during germination. Divide the seeds into two equal groups. Kill one group of seeds by boiling them, and then wash them with dilute formalin or carbolic acid to prevent bacterial decay. Put 2. What is the use of the following in the experiments the live germinating seeds in flask (A) and the killed ones on respiration ? in flask (B). Insert a thermometer in each flask and plug (1) Soda lime their mouths with cotton wool. After a few hours, the thermometer in flask-A will show a higher reading, thus indicating that the germinating (live and respiring) seeds (ii) Limewater give out heat. The thermometer in flask (B) will not show any rise in temperature. 3. Suppose we conduct an experiment to demonstrate 5. Experiment to demonstrate anaerobic respiration. respiration in a green plant. what special precaution Take eight to ten soaked and peeled off peas and push is required to be taken in it ? them into the mouth of a test-tube filled with mercury and 4. In experiment No. 5 we are using mercury in the test- inverted in a beaker of mercury. The seeds will float to the tube and the beaker. Why can't we use water instead ? top and will be completely surrounded by mercury. After about two days, the level of mercury in the test-tube will fall (Fig. 7.7) and the liberated gas will be found to be 54 Downloaded from https:// www.studiestoday.com  Downloaded from https:// www.studiestoday.com 7.6 RESPIRATION CONTRASTED WITH PHO- there is no gaseous transport, the respiratory TOSYNTHESIS (1) gases simply diffuse in and out by cell to cell In many respects, respiration and photosynthesis diffusion. (In animals, the blood transports in plants are distinctly opposite processes. The respiratory gases). requirements of one are the products of the other and one of the end products of anaerobic respiration (ii) therefore, they are complementary to each other. This in plants is ethanol/ethyl alcohol while in is the reason why we cannot conduct an experiment animals it is lactic acid. on plant respiration during daytime, in light. The (111) in plants the process produces little heat as fundamental differences between plant respiration and compared to animals. photosynthesis are given in Table 7.2. Respiration opposite of photosynthesis. PROGRESS CHECK In the differences mentioned in Table 7.2 below, 1. Fill in the blanks. there are at least five points in which photosynthesis In anaerobic respiration in plants, the end product and respiration are exactly opposite to each other. is and instead of lactic Can you make out these points? in animals. Table 8.2 Photosynthesis and Respiration Contrasted 2. The table below is intended to give certain differences between photosynthesis and respiration, PHOTOSYNTHESIS RESPIRATION but a few points are given wrongly. Strike out the 1. Occurs only in the Occurs in all living cells. wrong ones and write the correct words instead. presence of chlorophyll. PHOTOSYNTHESIS RESPIRATION 2. Occurs only in the Occurs at all times. (i Results in loss Results in gain presence of light. in weight in weight 3. Uses carbon dioxide Uses oxygen and (ii) Sucrose is the Sucrose is and water. glucose. product broken down 4. Oxygen is released Carbon dioxide is (iii) Occurs in green Occurs in all as an end product. released as end product. cells only cells 5. Light energy is Chemical energy is partly (iv) Uses water and Uses glucose and converted into converted into heat and oxygen oxygen chemical energy partly into useful energy and stored. for various activities. Why one should not sleep under a tree at night 6.Results in gain in weight. Results in weight loss. — CO, or something else ? Food (glucose) Food (glucose) broken The carbon dioxide manufactured. down (oxidised, released by trees during (Constructive destructive or katabolic) respiration at night is too process, anabolic) little to cause any harm (we have much more of this gas in our bed rooms). 7.7 RESPIRATION IN PLANTS COMPARED However, the droppings of WITH RESPIRATION IN ANIMALS the perching birds and the The basic aspects of respiration are same in all night-active insects, organisms. However, there are some differences in spiders, snakes, etc., are real dangers. But believe it respiration in plants and animals. For example, in there are no ghosts or spirits resting on the trees. plants : 55 Downloaded from https:// www.studiestoday.com  Downloaded from https:// www.studiestoday.com POINTS TO REMEMBER > Respiration is the breakdown of glucose to yield energy in the form of ATP. The breakdown of glucose occurs in two major phases : glycolysis and Krebs cycle. > Respiration occurs in a series of steps carried out by enzymes > The plants have three inlets of oxygen from the atmosphere — stomata in leaves, lenticels in stem and the general surface of the root. › There are two kinds of respiration — aerobic using oxygen and releasing CO, H,0 and energy (ATP), and anaerobic, in absence of oxygen, releasing ethanol (C,H,OH), CO, and energy. > Aerobic respiration occurs normally thoughout life, whereas anaerobic respiration occurs temporarily for short periods. Respiration in plants is opposite to photosynthesis in several features e.g. gases used and released, gain or loss in weight. REVIEW QUESTIONS A. MULTIPLE CHOICE TYPE (a) Aerobic respiration of one mole of glucose 1. Glycolysis is a process yields 138 ATP (T/F) (a) in which glycogen is broken down into glucose (b) Anaerobic respiration in plants yields lactic (b) which occurs in mitochondria acid. (T/F) (c) in which glucose is broken down into pyruvate (c) Carbon dioxide readily dissolves in lime (d) that occurs next to Krebs cycle. water. (T/F) 2. One same common function is performed by ? (d) All leaves of a green plant normally respire (a) Stomata and veins anaerobically at night. (T/F) (b) Stomata and lenticels C. SHORT ANSWER TYPE (c) Lenticels and sepals 1. What happens to the energy liberated in respiration ? (d) Lenticels and hydathodes 2. inWhy is it usually difficult to demonstrate respiration 3. Anaerobic respiration normally occurs in green plants ? (a) Grass (b) Cactus (c) Coconut (d) Baker's yeast 3. Explain why respiration is said to be the reverse of photosynthesis. B. VERY SHORT ANSWER TYPE 4.How is the tilling of the soil useful for the crops 1. Do the plants respire all day and all night or only at growing in it? night ? 5. Write the full form of ATP and ADP. 2. Name the following : 6. Can cell respiration occur in any organism at a temperature of about 65°C ? Give reason. (a) Energy currency of cell. (b) Oxidative breakdown of carbohydrates to 7. Fill in the blanks : release energy. (a) are the openings found on older stems. (c) An organism which respires throughout life (b) Glycolysis occurs in the....... of the cells. anaerobically. (c) is a respiratory substance. (d) A common phase in both aerobic and (d) Rate of is more than the rate of anaerobic respiration.... in the daytime in the case of green plants. (e) Aerobic respiration requires (e).. is a chemical which absorbs oxygen (1) A chemical which removes CO, from the air. of the air. Mention if the following statements are true or false. (f) is used to create vacuum to show If false, rewrite them correctly. anaerobic respiration. Downloaded from https:// www.studiestoday.com  Downloaded from https:// www.studiestoday.com D. LONG ANSWER TYPE (a) In how many flasks, the different plant parts have been kept under observation? 1. What is respiration ? How are respiration and burning similar and how are they different? (b) What is the purpose of keeping a test-tube 2. How are aerobic and anaerobic respirations different containing limewater in each flask? in plants ? (c) In which tube/tubes the limewater will turn Describe one experiment each you would perform milky? 3. (d) What is the purpose of the set-up F? to demonstrate the following phenomena: The germinating seeds (a) produce heat, (b) give out (e) What conclusion can you draw from this carbon dioxide, (c) can respire even in total absence experiment? of air. 2. The following two chemical reactions are supposed 4. How do the following structures help in respiration to indicate a certain process occurring in the green in plants? plants under two different conditions : (a) Lenticels (a) CH,206 + 602 → 6000 , +...... + 38 ATP (b) Stomata (b) C6 4,2% →...+ 2CO, + 2ATP (c) Root hairs (i) Fill in the blank in each reaction. (ii) Name the process represented by the two E. STRUCTURED/APPLICATION/SKILL reactions. (iii) What are the conditions under which the 1. Given below is a set of six experimental set-ups two reactions (a) and (b) are occurring (A-F), kept in this state for about 24 hours. respectively? STOPPER STOPPER - THREAD THREAD THREAD CONICAL FLASK CONICAL FLASK TEST-TUBE TEST-TUBE TEST-TUBE FLOWERS LIMEWATER LIMEWATER LIMEWATER FRUITS' LEAVES B STOPPER — STOPPER THREAD THREAD THREAD CONICAL FLASK. CONICAL FLASK - TEST-TUBE TEST-TUBE TEST-TUBE PIECES OF NO PLANT STEM PART IS PUT LIMEWATER LIME-WATER IN HERE ROOTS LIME- WATER D E F Downloaded from https:// www.studiestoday.com  Downloaded from https:// www.studiestoday.com 3. isThe following diagram refers to an apparatus which used to demonstrate a physiological process : (b) What is the function of soda lime in the bottle 'A' and why is limewater placed in bottle 'B'? GERMINATING (c) What change would you expect to observe in PEAS (SUP- bottle 'D'? PORTED ON WIRE MESH) TUBING TUBING (d) Represent the physiological process named in BOILED PEAS 1 2 SOAKED IN (a) above in the form of a chemical equation. DISINFECTANT (e) In order to obtain accurate results, the bottle 'C' should be covered with a piece of black cloth. Why? TEST-TUBE-X. TEST- TUBE Y (f) If bottle 'C" was fitted with a 3-holed rubber stopper and a thermometer were introduced POTASSIUM POTASSIUM HYDROXIDE in such a way that its bulb reaches close to HYDROXIDE (Experiment) (Control) SOLUTION the germinating seeds, what would you SOLUTION observe? Why? COLOURED JUDGE THE TRUTH WATER The relationship between Flowers, Fruits (a) What is the purpose of keeping potassium hydroxide solution in the test tubes X and Y? (b) Why has the coloured water risen in tubing 1? (c) What is the purpose of keeping boiled peas And soaked in a disinfectant in test tube Y? Humans (d) Name the biological process which causes the above rise. (e) Define the biological process shown in the Animals experiment. In order to study and prove a particular physiological process in plants, the following experiment was set up. Study the same and then answer the questions Flowers: Plants produce flowers with To attract insects that follow : Colour Fragrance and birds to feed Nectar (honey) on nectar "Selfish interest" of plants - Pollination Fruits : Plants produce fruits with Tasty flavour Humans and animals Fleshy pulp (as food) are attracted and eat them "Selfish gain" to the plants - Seeds thrown away here and there. (Dispersal) So, Are the plants kind and benevolent ? SODA LIME LIMEWATER GERMINAT- LIMEWATER ING SEEDS OR Truly Selfish? (a) Name the physiological process being [Answer...... studied. Downloaded from https:// www.studiestoday.com