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Biology > Nutrition In Plants > Flashcards

Nutrition In Plants Flashcards

0
Q

Which substance is a reactant as well as a product in photosynthesis?

A

Water.

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1
Q

Define ‘Photosynthesis’.

A

Process by which energy from sun transformed into chemical energy in form of carbohydrate molecules, where carbon dioxide and water react together using sunlight absorbed by chlorophyll to produce glucose and oxygen.

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2
Q

The photosynthetic process occurs in the chloroplast in which 2 stages?

A
  1. Light reaction

2. Dark reaction.

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3
Q

Describe the light reaction in photosynthesis.

A
  1. Light dependent stage which requires light energy.
  2. During LR, photolysis of water takes place, using light energy trapped by chlorophyll present in chlorophyll.
  3. Light energy also converted into chemical energy in form of ATP.
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4
Q

What is photolysis?

A

Photochemical splitting of water molecules into hydrogen and oxygen.

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5
Q

Describe the dark reaction in photosynthesis.

A
  1. CO2 reduced by hydrogen(produced in light reaction) to form glucose using ATP produced in light stage.
  2. A temperature dependent stage as enzymes are involved.
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6
Q

How does carbon dioxide enter the leaf?

A

Carbon dioxide from atmosphere diffuses into leaf through stomata.

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7
Q

What happens once CO2 enters the leaf?

A

It dissolves in thin film of water surrounding spongy mesophyll cells and palisade mesophyll cells and finally diffuse into chloroplasts within cells and used in photosynthesis.

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8
Q

What are the factors affecting photosynthesis rate?

A
  1. Light intensity
  2. Temperature
  3. Carbon dioxide conc.
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9
Q

What happens to photosynthesis rate at very high light intensities?

A

Photosynthesis rate slows down as excessive amount of ultra violet rays damages chlorophyll molecules.

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10
Q

What happens to photosynthesis rate beyond light saturation point?

A

Further increase in light intensity has no effect on photosynthesis rate.

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11
Q

What happens to photosynthesis rate at higher light intensities?

A

Net uptake of CO2 and release of oxygen is reached and amount of sugar in plant will increase.

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12
Q

What happens to photosynthesis rate as light intensity increases?

A

Photosynthesis rate increases until amount of carbon dioxide released from respiration is equal to amount of carbon dioxide absorbed for photosynthesis.

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13
Q

What happens to photosynthesis rate in the absence of light?

A

Photosynthesis does not occur and only respiration occurs.

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14
Q

What happens to photosynthesis rate when temperature is increased up to 40 degrees?

A

Increasing temperature up to 40 degrees will increase photosynthesis rate due to increases enzyme activity.

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15
Q

What happens to photosynthesis rate when temperature is increased to above 40 degrees ?

A

Rate of photosynthesis slows down as enzymes are denatured gradually.

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16
Q

What happens to photosynthesis rate when CO2 concentration is increased?

A
  1. Increasing CO2 level increases rate of photosynthesis up to CO2 saturated point.
  2. Further increase in CO2 levels no effect on photosynthesis rate.
17
Q

How is a plant destarched?

A
  1. Keep them in the dark for 48hrs
  2. In absence of photosynthesis, all starch stored in leaves will be converted into sugar, carried away and utilized by other parts of plants.
18
Q

Describe the starch test.

A
  1. Boil leaf for 2 mins to kill cells.
  2. Place boiled leaf in ethanol to extract chlorophyll as ethanol dissolves lipids in cell membrane.
  3. Soften leave in hot water for penetration of iodine.
  4. Treat leaf with iodine on white tile
  5. Regions turn blue indicates presence of starch.
19
Q

How is carbon dioxide removed in a closed area?

A

Using potassium hydroxide solution.

20
Q

What are the limiting factors of photosynthesis?

A
  1. Light.
  2. CO2 concentration.
  3. Temperature.
21
Q

How is the leaf well adapted for its functions?

A
  1. Broad and flat shape provides large surface area to trap Max amount of light energy& absorb max amount of CO2.
  2. Very thin, light can penetrate and reach all cells, CO2 diffuse rapidly.
  3. Leaves positioned at angle so they receive Max amount of light without overshadowing each other.
22
Q

What is the structure of the upper epidermis?

A
  1. One cell thick layer.
  2. Waxy cuticle.
  3. No chlorophyll.
  4. Stomata may be present in small numbers.
23
Q

What is the function of the upper epidermis?

A
  1. Cuticle reduces loss of water through evaporation.
  2. Cuticle protects leaf from mechanical damage.
  3. Upper epidermis and cuticle is transparent, thus allowing light to pass through easily.
24
Q

Describe the structure of the palisade mesophyll.

A
  1. Densely packed cylindrical shaped cells arranged at right angles to upper epidermis of leave in 1 or 2 layers.
  2. Cells have thin walls and contain many chloroplasts.
25
Q

What is the function of the palisade mesophyll?

A
  1. Palisade mesophyll cells are main sites where photosynthesis takes place due to high concentration of chlorophyll.
  2. Thin cell wall and cytoplasm allows rapid diffusion of water and carbon dioxide into chloroplasts.
26
Q

Describe the structure of the spongy mesophyll.

A
  1. Irregularly shaped cells containing fewer chloroplasts.

2. Cells loosely packed with large intercellular air spaces between cells.

27
Q

What is the function is the spongy mesophyll?

A
  1. Air spaces connected with stomata- serves as passage way for diffusion of CO2 and O2, as well as water vapor.
  2. Some photosynthesis occurs and this causes cells to be turgid- support.
28
Q

Describe the structure of the vascular bundles.

A
  1. Lignified xylem vessels and tracheids.

2. Phloem tissues with sieve tubes and companion cells.

29
Q

What are the functions of the vascular bundles?

A
  1. Xylem aids in conduction of water &mineral salts from roots to leaves.
  2. Provides support for lead lamina
  3. Phloem aids in transport of products of photosynthesis from leaves to other parts of plant, esp to roots, in form of sucrose.
30
Q

Describe the structure of the lower epidermis.

A
  1. One cell thick layer.
  2. Waxy cuticle.
  3. Presence of many stomata.
31
Q

What is the function of the lower epidermis?

A

Stomata allows gaseous exchange between external environment and intercellular air spaces in spongy mesophyll.

32
Q

Describe the structure of the stomata.

A

A pair of curved guard cells surrounding a stomatal pore.

33
Q

What are the functions of the stomata?

A
  1. Gaseous exchange occurs through stomatal pore.

2. Opening or closure of guard elks regulates gaseous exchange.

34
Q

How is glucose formed during photosynthesis used immediately?

A
  1. For cellular respiration to provide energy for cellular activities.
  2. To form cellulose cell walls.
35
Q

What happens to guard cells in sunlight?

A
  1. GC photosynthesise, converting LE to CE.
  2. CE uses to pump potassium ions into GC from epidermal cells.
  3. Water potential of GC lowered.
  4. Water from EC enter GC by osmosis.
  5. Increase turgidity of GC and caused them to be swollen.
  6. Swollen GC becomes curved and pull stoma open.
36
Q

What happens to the guard cells at night?

A
  1. Potassium ions that have accumulated in GC during say diffuses out of GC.
  2. Water potential in GC increased.
  3. Water leaves cells by osmosis.
  4. GC becomes flaccid and stoma closes.
37
Q

Explain how carbon dioxide and water enter the leaves.

A
  1. CO2 rapidly used up during photosynthesis.
  2. CO2 conc in leaf is lower in than air, diffusion gradient exists.
  3. CO2 diffuses from surrounding air through stomata into air spaces of leaf.
  4. Surfaces of mesophyll cells always covered by thin film of water so CO2 can dissolve in it.
  5. Dissolved CO2 diffuse into cells.
38
Q

How is the glucose formed during photosynthesis used immediately ?

A
  1. Cellular respiration to provide energy for cellular activities.
  2. Form cellulose cell walls
39
Q

Why do plants convert glucose into starch and how is it used later?

A
  1. In daylight, photosynthesis rate is so great that sugars formed faster than they can be removed. Excess glucose converted into starch.
  2. In darkness, photosynthesis stops and starch converted by enzymes back into glucose.
40
Q

Why is glucose converted into sucrose before it can be transported away from the leaves?

A

By forming the more complex sugar, the plant is able to store energy more efficiently in a more compared form compared to glucose, a monosaccharide.

Biology (10 decks)

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