Life Processes in Plants

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(d) (oxygen is released, not required, for photosynthesis)

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(d)

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starch

chlorophyll

iodine

carbon dioxide

photosynthesis

glucose

stomata

xylem

phloem

Energy

respiration

Vrikshayurveda

Oxygen

Neera

food

True

False (chlorophyll is essential for preparing starch in the presence of sunlight)

True

False (no starch is produced in the absence of sunlight)

True

True

False (photosynthesis occurs in the presence of sunlight)

False (all parts of a plant, green or non-green, carry out respiration)

True

True

True

False (in the activity the peel is taken from the lower surface of the leaf where stomata are observed)

True

False (photosynthesis makes food using sunlight; respiration breaks down glucose to release energy)

True

(i)–(c), (ii)–(a), (iii)–(b), (iv)–(e), (v)–(d)

(i)–(e), (ii)–(c), (iii)–(a), (iv)–(b), (v)–(d)

(d)

(a)

(d)

(b)

(c) (Alcohol must never be placed near a direct heat source; the test tube of alcohol is heated in a beaker of boiling water)

(a) (Xylem transports water and minerals; phloem transports food)

(d)

(a)

Hint: Sunlight, water, chlorophyll, and carbon dioxide.

Hint: Leaves are the primary site of photosynthesis where food (starch) is prepared using sunlight, water, carbon dioxide, and chlorophyll.

Hint: Chlorophyll is the green pigment that captures sunlight efficiently; it is essential for the preparation of starch in the presence of sunlight.

Hint: Boiling in water softens the leaf; dipping in alcohol (heated in a water bath) decolourises the leaf so that the colour change with iodine can be easily observed.

Hint: Alcohol is highly flammable and can easily lead to fire and burns; it must be heated only indirectly in a beaker of boiling water.

Hint: Carbon dioxide + Water → Glucose + Oxygen (in the presence of sunlight and chlorophyll).

Hint: Glucose + Oxygen → Carbon dioxide + Water + Energy.

Hint: Tiny pores on the surface of leaves; they help in the exchange of gases (oxygen and carbon dioxide) during photosynthesis and respiration; observed on a peel from the lower surface of the leaf.

Hint: Xylem — transports water and minerals from roots to leaves and other parts; Phloem — transports food prepared in the leaves to all parts of the plant.

Hint: The xylem carried the red ink (dissolved like minerals in water) upward from the stem; it shows that water and dissolved minerals move up through the xylem.

Hint: Food is synthesised in the leaves (photosynthesis); it is transported to the potato (a storage part) through the phloem, where it is stored as starch.

Hint: Yes — all parts of a plant respire; evidence: in Activity 10.8, lime water connected to germinating moong bean seeds kept in the dark turned milky, showing the seeds released carbon dioxide during respiration.

Hint: The energy is used by plants for their growth and development.

Hint: It absorbs carbon dioxide from the air inside the bottle, so the part of the leaf inside the bottle cannot make starch — showing that CO₂ is essential for photosynthesis.

Hint: He studied the process of photosynthesis in India, examining the effects of the amount of water, temperature, and the colour of light on photosynthesis.

Hint: She received a Ph.D. from Cambridge for her work on respiration in plants; she improved the nutritive values of plant foods and worked on the coconut palm sap drink called Neera.

Hint: In the absence of sunlight, no starch was produced in the leaf, even though chlorophyll was present; hence no blue-black colour appeared.

Hint: It indicates that the gas collected is rich in oxygen, showing that oxygen is released during photosynthesis.

Hint: The carbon dioxide produced during respiration is used for photosynthesis, and the oxygen produced during photosynthesis is used for respiration — maintaining a balance of gases inside.

Hint: Photosynthesis takes in carbon dioxide and releases oxygen, while respiration takes in oxygen and releases carbon dioxide.

Introduction: Activity 10.1 investigates the role of sunlight and water in the growth of plants using saplings in three pots kept under different conditions.
Key Points:
1. Three set-ups — Pot A (sunlight + water), Pot B (sunlight, no water), and Pot C (dark + water) are observed for two weeks.
2. Pot A grows best — The plant in direct sunlight with adequate water shows maximum growth in height and leaves.
3. Pot B dies, Pot C grows poorly — The plant without water dies; the plant in the dark grows weakly and turns yellow.
Conclusion: Both sunlight and water are essential for the healthy growth of plants.

Introduction: The starch test uses iodine solution to detect the presence of starch stored in a green leaf.
Key Points:
1. Boiling and alcohol dip — The leaf is boiled in water, then kept in alcohol using a water bath to remove the green chlorophyll.
2. Iodine test — Diluted iodine is dropped on the decolourised leaf; a blue-black colour confirms starch is present.
3. Why decolourised — Removing chlorophyll makes the colour change easy to observe, as green colour would hide the result.
Conclusion: Decolourisation allows the blue-black iodine-starch reaction to be seen clearly.

Introduction: Bhaskar tested leaves with green and non-green patches from plants kept in sunlight and in the dark to study starch formation.
Key Points:
1. Variegated leaves tested — Leaves from a sunlit plant and a dark-kept plant were traced and given the iodine test.
2. Sunlit green patches turn blue-black — Only green patches of the sunlit leaf showed starch; non-green patches did not.
3. Dark leaf shows no starch — Even green patches of the dark-kept leaf did not turn blue-black, showing no starch was produced.
Conclusion: Chlorophyll and sunlight together are essential for the preparation of starch in leaves.

Introduction: This experiment uses caustic soda to absorb carbon dioxide from one part of a leaf to test whether it is needed for photosynthesis.
Key Points:
1. Destarched leaf in bottle — Half of a destarched leaf is placed inside a bottle containing caustic soda, which absorbs carbon dioxide.
2. Kept in sunlight — The set-up is placed in sunlight for a few hours, then the leaf is tested with iodine.
3. Outside part turns blue-black — The part outside the bottle shows starch; the part inside does not, showing carbon dioxide is essential.
Conclusion: Carbon dioxide from the air is necessary for plants to prepare starch by photosynthesis.

Introduction: A water plant placed in sunlight releases bubbles of gas, which are collected and tested to identify oxygen.
Key Points:
1. Set-up in sunlight — A water plant in a beaker is covered with a funnel and inverted test tube and kept in sunlight.
2. Bubbles collect — Air bubbles rise and accumulate in the inverted test tube during photosynthesis.
3. Matchstick test — A lit matchstick inserted into the gas burns with an intense flame, confirming the gas is oxygen.
Conclusion: Oxygen is released by plants during the process of photosynthesis in the presence of sunlight.

Introduction: Photosynthesis and respiration are opposite processes in plants involving different gas exchanges.
Key Points:
1. Photosynthesis equation — Carbon dioxide + Water → (Sunlight, Chlorophyll) → Glucose + Oxygen.
2. Respiration equation — Glucose + Oxygen → Carbon dioxide + Water + Energy.
3. Gas exchange difference — Photosynthesis takes in carbon dioxide and releases oxygen; respiration takes in oxygen and releases carbon dioxide.
Conclusion: The two processes use and release opposite gases, balancing each other in nature.

Introduction: Water and minerals absorbed by roots are carried to all parts of the plant through a specialised tissue.
Key Points:
1. Absorbed by roots — Roots take up water along with dissolved minerals from the soil.
2. Transported by xylem — Thin tube-like tissues called xylem carry water and minerals upward to leaves and other parts.
3. Red ink activity — When a twig is placed in red-coloured water, the red colour appears in the stem, leaves, and flowers, proving xylem transport.
Conclusion: The xylem tissue transports water and minerals from roots to all parts of the plant.

Introduction: Stomata are tiny pores on the leaf surface that can be observed by examining a leaf peel under a microscope.
Key Points:
1. Peel prepared — A thin peel from the lower surface of a leaf (e.g., rhoeo) is placed on a slide with a drop of ink.
2. Observed under microscope — Covered with a coverslip, tiny pores called stomata become visible under the microscope.
3. Function — Stomata allow the exchange of gases, taking in carbon dioxide and releasing oxygen during photosynthesis.
Conclusion: Stomata on leaf surfaces help plants exchange gases required for photosynthesis and respiration.

Introduction: Germinating seeds kept in a flask are used to show that plants respire and release carbon dioxide.
Key Points:
1. Seeds in flask — Soaked moong bean seeds are placed on wet cotton in a conical flask fitted with tubes.
2. Connected to lime water — The flask is left in the dark for 24 hours and connected to test tubes of lime water.
3. Lime water turns milky — The lime water connected to the flask turns milky, confirming the release of carbon dioxide by the respiring seeds.
Conclusion: Plants respire by breaking down glucose and releasing carbon dioxide, just like animals.

Introduction: Photosynthesis and respiration are complementary processes that together maintain the balance of gases in nature.
Key Points:
1. Photosynthesis releases oxygen — Plants produce oxygen during photosynthesis, which all living beings need for respiration.
2. Respiration releases carbon dioxide — Animals and plants release carbon dioxide during respiration, used by plants for photosynthesis.
3. Gas balance maintained — The two processes keep the levels of oxygen and carbon dioxide balanced in the atmosphere.
Conclusion: Photosynthesis and respiration together sustain life by maintaining the balance of oxygen and carbon dioxide in nature.

Introduction: The leaf is specially designed as the main site where photosynthesis takes place in a plant.
Key Points:
1. Broad and flat — Leaves have a large surface area that captures maximum sunlight for photosynthesis.
2. Contains chlorophyll — The green pigment chlorophyll in leaves absorbs sunlight energy needed to make food.
3. Other green parts also photosynthesise — Yes, other green parts of the plant that contain chlorophyll can also perform photosynthesis.
Conclusion: The leaf is the primary site of photosynthesis, but any green part with chlorophyll can also make food.

Introduction: Kamala Sohonie was a noted Indian woman scientist who studied respiration in plants and improved the nutritive value of plant foods.
Key Points:
1. Ph.D. on plant respiration — She received a Ph.D. from Cambridge University for her work on respiration in plants.
2. Improved plant food nutrition — Her work helped improve the nutritive values of plant foods and the coconut sap drink Neera.
3. Institutions worked at — She worked at the Lady Hardinge Medical College, New Delhi, and the Royal Institute of Science, Bombay.
Conclusion: Kamala Sohonie made important contributions to plant respiration and nutrition science in India.

Introduction: A leaf needs sunlight to carry out photosynthesis and produce starch, as shown by the iodine test.
Key Points:
1. Dark-kept leaf lacks sunlight — Without sunlight, the plant kept in the dark could not perform photosynthesis to make starch.
2. Sunlit leaf produces starch — The plant kept in sunlight had both chlorophyll and sunlight, so it produced starch in its leaves.
3. Iodine test confirms — The sunlit leaf turned blue-black with iodine, while the dark-kept leaf showed no colour change.
Conclusion: Sunlight is essential for starch production in leaves through photosynthesis.

Introduction: The starch in a potato is made in the leaves and transported to the potato for storage.
Key Points:
1. Food made in leaves — Starch is synthesised in the green leaves by the process of photosynthesis using sunlight and chlorophyll.
2. Transported by phloem — The food prepared in the leaves is carried to the potato through thin tube-like tissues called phloem.
3. Stored in potato — The potato stores this transported food in the form of starch, which is why it turns blue-black with iodine.
Conclusion: Food is made in the leaves by photosynthesis and transported through the phloem to be stored in the potato.

Introduction: Photosynthetic organisms are the main source of food and oxygen for all living beings on Earth.
Key Points:
1. Food supply stops — Without photosynthesis, no food would be produced, and herbivores would starve first.
2. Oxygen levels fall — No oxygen would be released, causing all animals and humans to suffocate over time.
3. Food chains collapse — Without plants, the entire food chain would break down, leading to the death of all living organisms.
Conclusion: The disappearance of photosynthesising organisms would eventually destroy all life on Earth.

Hint: (a) The presence of starch. (b) In the absence of sunlight, no photosynthesis occurred, so no starch was produced. (c) Sunlight is essential for starch production, and chlorophyll is essential — only green patches (with chlorophyll) in sunlight produced starch; non-green patches lacked sufficient chlorophyll.

Hint: (a) To destarch the plant — to make it lose any stored starch so that the result reflects only new starch made during the experiment. (b) Caustic soda absorbs carbon dioxide from the air inside the bottle. (c) It shows that carbon dioxide is essential for plants to prepare starch; the part inside had no CO₂ so could not make starch, while the part outside (with CO₂) did.

Hint: (a) In the set-up kept in sunlight; it indicates that a gas is being produced during photosynthesis. (b) The gas is rich in oxygen (oxygen supports burning, giving an intense flame). (c) Oxygen is released during photosynthesis, and photosynthesis occurs in the presence of sunlight; the dark set-up had no sunlight, so no photosynthesis occurred and no gas (oxygen) was released.

Hint: (a) The xylem. (b) Minerals dissolved in water. (c) The phloem transports food prepared in the leaves to all parts of the plant; the food may also be stored in some parts such as seeds and roots (e.g., potato).

Hint: (a) To ensure the seeds were respiring and not photosynthesising (no sunlight), so any gas change is due to respiration. (b) Carbon dioxide released by the respiring seeds reacts with lime water, turning it milky. (c) It shows that plants respire and release carbon dioxide; word equation: Glucose + Oxygen → Carbon dioxide + Water + Energy.

Hint: (a) Whether sunlight is necessary for the production of starch (photosynthesis). (b) The plant in sunlight would look healthy/green; the plant kept in the dark may look weak and its leaves may turn yellowish or wilt over time. (c) The leaves of the plant kept in sunlight would turn blue-black with iodine, because with sunlight (and chlorophyll and CO₂) it carried out photosynthesis and produced starch; the dark plant produced no starch.

Hint: (a) The snail, because it respires and releases carbon dioxide. (b) The water plant, because it photosynthesises and uses carbon dioxide. (c) In test tube C, the CO₂ released by the snail is used by the plant for photosynthesis, so the indicator may show less change (balance); in test tube D (water only) there is no organism, so no change acts as a control. Ananya is testing the exchange of gases — that animals give out CO₂ and plants use it.

Hint: (a) Respiration and photosynthesis. (b) The plant itself produces carbon dioxide during respiration, which it then uses for photosynthesis. (c) The carbon dioxide produced during respiration is used for photosynthesis, and the oxygen produced during photosynthesis is used for respiration — so the two processes maintain a balance of gases inside the sealed bottle, letting the plant survive.

Hint: (a) Glucose, a simple carbohydrate. (b) Starch. (c) Necessary: sunlight, water, chlorophyll, carbon dioxide. Products: glucose and oxygen.

Hint: (a) They contain more of other coloured pigments than the green chlorophyll, which hides the green colour. (b) Chlorophyll captures sunlight efficiently and is essential for the preparation of starch. (c) Perform the starch test (decolourise the leaf in alcohol, then add iodine); if the leaf turns blue-black, it indicates the presence of starch, confirming that photosynthesis has taken place.

Introduction: The starch test is performed on a leaf to confirm whether it has produced starch through photosynthesis.
Key Points:
1. Boil leaf in water — Boiling softens the leaf and breaks open the cell walls so that tests can work properly.
2. Dip in alcohol using water bath — Alcohol removes the green chlorophyll and decolourises the leaf, making colour changes visible.
3. Wash and spread the leaf — Washing softens the brittle leaf and spreads it flat for even testing on a plate.
4. Add iodine solution — Diluted iodine turns blue-black if starch is present, confirming that photosynthesis occurred.
5. Safety precaution for alcohol — Alcohol is highly flammable, so it must never be heated directly over a flame; use a water bath.
Conclusion: Each step of the starch test is necessary to clearly observe the blue-black colour that confirms the presence of starch.

Introduction: Photosynthesis is the process by which green plants prepare their own food using sunlight, carbon dioxide, water, and chlorophyll.
Key Points:
1. Definition and site — Photosynthesis occurs mainly in green leaves, which act as the food factories of the plant.
2. Word equation — Carbon dioxide + Water → (Sunlight, Chlorophyll) → Glucose + Oxygen.
3. Raw materials — Carbon dioxide from air, water from soil, sunlight, and chlorophyll are required.
4. Products — Glucose (food), which is later stored as starch, and oxygen gas are produced.
5. Importance for life — It provides food for all organisms and oxygen for respiration, supporting all life on Earth.
Conclusion: Photosynthesis is vital because it supplies food and oxygen that sustain every living organism on Earth.

Introduction: An experiment using caustic soda to absorb carbon dioxide proves that it is essential for photosynthesis.
Key Points:
1. Destarching the plant — The potted plant is kept in the dark for two to three days so that it loses any stored starch.
2. Purpose of destarching — This ensures that any starch found later is newly made during the experiment, not previously stored.
3. Leaf in caustic soda bottle — Half of a destarched leaf is inserted into a bottle of caustic soda, which absorbs carbon dioxide.
4. Set-up in sunlight — The plant is kept in sunlight for a few hours, then the leaf is tested with iodine.
5. Result proves the point — The part outside turns blue-black (starch present); the part inside does not, proving carbon dioxide is essential.
Conclusion: This experiment shows that carbon dioxide is necessary for plants to carry out photosynthesis.

Introduction: Plants have specialised tissues called xylem and phloem that transport water, minerals, and food to all parts.
Key Points:
1. Xylem transports water and minerals — Roots absorb water and minerals, which move upward through xylem tubes to leaves.
2. Phloem transports food — Food made in the leaves is carried to stems, roots, and seeds through phloem tubes.
3. Red ink activity — Two twigs are placed in tumblers of water, one with red ink added to it.
4. Observation next day — Red colour appears in the stem, leaves, and flowers of the twig kept in red ink.
5. Cut stem shows xylem — Cutting the stem reveals red colour in tube-like xylem, proving water transport.
Conclusion: The xylem transports water and minerals upward, while the phloem transports food from leaves to all plant parts.

Introduction: Photosynthesis and respiration are two opposite life processes in plants that balance gases in nature.
Key Points:
1. Raw materials differ — Photosynthesis uses carbon dioxide and water; respiration uses glucose and oxygen.
2. Products differ — Photosynthesis produces glucose and oxygen; respiration produces carbon dioxide, water, and energy.
3. Energy role — Photosynthesis stores energy from sunlight; respiration releases energy from glucose for growth.
4. Gas exchange opposite — Photosynthesis takes in carbon dioxide and releases oxygen; respiration does the reverse.
5. Balance maintained — Together they keep oxygen and carbon dioxide levels stable in the atmosphere.
Conclusion: Photosynthesis and respiration are complementary processes that maintain the balance of oxygen and carbon dioxide in nature.

Introduction: An experiment with a water plant shows that oxygen gas is released during photosynthesis in sunlight.
Key Points:
1. Water plant in beaker — A water plant is placed in a beaker of water under a funnel with an inverted test tube.
2. Kept in sunlight — The set-up is placed in sunlight, where the plant carries out photosynthesis.
3. Bubbles collect — Air bubbles rise from the plant and accumulate in the inverted test tube.
4. Gas tested with matchstick — A lit matchstick inserted into the collected gas burns with a bright, intense flame.
5. Gas identified as oxygen — The glowing matchstick confirms the collected gas is oxygen, released during photosynthesis.
Conclusion: This experiment proves that oxygen is released by plants during photosynthesis in the presence of sunlight.

Introduction: Respiration is the process by which plants break down glucose to release energy, using oxygen and releasing carbon dioxide.
Key Points:
1. Respiration in all parts — All parts of a plant, green or non-green, carry out respiration to obtain energy.
2. Word equation — Glucose + Oxygen → Carbon dioxide + Water + Energy.
3. Activity with seeds — Soaked moong seeds are kept on wet cotton in a flask fitted with tubes connected to lime water.
4. Kept in the dark — The flask is left undisturbed in the dark for 24 hours to prevent photosynthesis.
5. Lime water turns milky — The lime water turns milky, confirming the seeds released carbon dioxide during respiration.
Conclusion: Plants respire by breaking down glucose and release carbon dioxide, using the energy released for their growth.

Introduction: The leaf is specially adapted to carry out photosynthesis efficiently through its structure and contents.
Key Points:
1. Broad and flat shape — The large surface area of the leaf captures maximum sunlight for photosynthesis.
2. Chlorophyll pigment — The green pigment chlorophyll absorbs sunlight energy needed to prepare food from raw materials.
3. Stomata for gas exchange — Tiny pores called stomata allow carbon dioxide to enter and oxygen to exit the leaf.
4. Veins transport materials — Veins contain xylem, which brings water, and phloem, which carries away the food made.
5. Thin structure — The thin leaf allows gases to diffuse in and out quickly during photosynthesis and respiration.
Conclusion: The structure of the leaf — its shape, chlorophyll, stomata, and veins — makes it perfectly suited for photosynthesis.

Introduction: Rustom Hormusji Dastur and Kamala Sohonie were Indian scientists who made important contributions to the understanding of plant life processes.
Key Points:
1. Dastur studied photosynthesis — Rustom Hormusji Dastur (1896–1961) studied the effects of water and temperature on photosynthesis.
2. Dastur's role on light — He examined the importance of water, temperature, and the colour of light in photosynthesis.
3. Dastur's position — He headed the Botany Department at the Royal Institute of Science, Bombay, from 1921 to 1935.
4. Sohonie's research — Kamala Sohonie earned a Ph.D. from Cambridge University for her work on respiration in plants.
5. Sohonie's contributions — She improved the nutritive value of plant foods, worked on the drink Neera, and became Director at the Royal Institute of Science, Bombay.
Conclusion: Both Dastur and Sohonie greatly advanced the study of photosynthesis and respiration in plants in India.

Introduction: Photosynthesising organisms are the foundation of food chains and the main source of oxygen in the atmosphere.
Key Points:
1. Food production stops — Without photosynthesis, no plants would make food, causing herbivores to starve and die.
2. Food chains collapse — With herbivores gone, carnivores would also lose their food, breaking down the entire food chain.
3. Oxygen levels fall — No oxygen would be released, gradually reducing the oxygen available for respiration in all animals.
4. Carbon dioxide rises — Without plants absorbing carbon dioxide, its level in the air would increase dangerously.
5. Life perishes — Eventually, the lack of food and oxygen would lead to the death of nearly all living organisms on Earth.
Conclusion: The disappearance of photosynthesising organisms would destroy food chains and unbalance the gases, ending life on Earth.