plant nutrition

Question 1

what is photosynthesis

Answer 1

process by which plants manufacture carbohydrates from raw materials using energy from light.

Question 2

photosynthesis word equation

Answer 2

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Question 3

photosynthesis symbol equation

Answer 3

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Question 4

how does CO2 enter a leaf

Answer 4

The carbon dioxide diffuses through the open stomata of the leaf of a plant and water is taken up through roots.

Question 5

use of chlorophyll for photosynthesis

Answer 5

Chlorophyll is a dye, which traps light energy and converts it into chemical energy for the formation of carbohydrates and their subsequent storage.

Question 6

experiment for need of chlorophyll for photosynthesis

Answer 6

Take a potted plant with variegated (green and white) leaves.

Destarch the plant by keeping it in complete darkness for about 48 hours.

Expose the plant to the sunlight for a few days.

Leaf boiled in water for 2 minutes to break down cell walls, denature enzymes and allow for easier penetration by ethanol.

Warmed in ethanol until leaf is colourless to extract chlorophyll, which would mask observation

Dipped in water briefly: to soften leaf

Leaf is placed on a white tile and iodine is added. If starch is present, colour will be blue-black and if absent, it will remain orange

Question 7

experiment for need for light in photosynthesis

Answer 7

Destarch the plant by keeping it in darkness for 48hrs

Place a stencil over part of a leaf

Place the leaf in sunlight for 4-6 hours

Remove the stencil and test for starch

+ve result = parts which received light turn black

-ve result = parts which didn’t receive light remain yellow/brown

Question 8

experiment for carbon dioxide need in photosynthesis

Answer 8

Take two destarched potted plants.

Cover both the plants with bell jars and label them as A and B.

Inside A, keep NaHCO­3 (sodium bicarbonate). It produces CO2.

Inside B, keep NaOH (Sodium hydroxide). It absorbs CO2.

Keep both the set-ups in the sunlight for at least 6 hours.

Perform the starch test on both plants.

The leaves of Plant A will turn black after the starch test

The leaves of Plant B will remain orange/brown after starch test

Question 9

what is a limiting factor

Answer 9

Limiting factor: something present in the environment in such short supply that it restricts life processes.

Question 10

light intensity as limiting factor

Answer 10

As the amount of light increases, the rate of photosynthesis increases (a-b)
The limiting factor is light
Increasing the amount of light after a certain point has no effect on the rate (c)
The limiting factor is now carbon dioxide or temperature

Question 11

carbon dioxide concentration as limiting factor

Answer 11

As the amount of carbon dioxide increases, the rate of photosynthesis increases (a-b)
The limiting factor is carbon dioxide
Increasing amount of carbon dioxide after a certain point has not effect on rate (c)
The limiting factor is now light or temperature (warmth)

Question 12

temperature as limiting factor

Answer 12

As temperature increases, the rate of photosynthesis increases until it reaches optimum temperature 40°C (a)
The limiting factor is the temperature
Increasing the temperature above 40°C will cause the enzymes to denature (b)
This will decrease rate of photosynthesis

Question 13

how is glasshouse systems adapted for plants

Answer 13

To increase the crop yield, farmers control the limiting factors:

CO2 enrichment: paraffin is burnt to increase CO2 concentration by three times the original amount and doubling the yield

Optimum temperature: thermostatically controlled heaters make the temperature right for enzymes to work

Optimum light: light has a high intensity for more photosynthesis, the correct wavelengths (red and blue not green) and duration controls production of fruit

Question 14

leaf structure

Answer 14

Cuticle: waxy layer that prevents water loss from top of the leaf

Epidermis: transparent cell that allows sunlight to pass through to the palisade cell

Palisade: found at the top of the cell and contains many chloroplasts which absorbs sunlight.

Spongy mesophyll layer: irregularly shaped cells which create air spaces to allow gaseous exchange to take place; do not contain many chloroplasts

Vascular Bundle: made up of xylem and phloem

Xylem: vessel which transports water and dissolved minerals and has lignified walls made of cellulose

Phloem: vessel which transports nutrients

Stomata: little holes that opens and closes to allow gaseous exchange to take place.

Question 15

how does stomata work

Answer 15

The stomata close to prevent water loss and open to let gases come in and out. When guard cells lose water, the stoma close (at night), while the stoma open when guard cells gain water & swell (during the day).

Question 16

Xylem function and characteristics

Answer 16

Unidirectional vessel which transports water and dissolved minerals.

Walls are made out of waterproof lignin.

Water moves up due to transpiration and osmosis

Question 17

phloem function and characteristics

Answer 17

Bidirectional vessel

Contains sieve elements which allow sugars to pass from one cell to next downwards

Contains companion cells which provide energy for active transport of sugars all over plant.

Translocation moves organic molecules (sugars, amino acids) from source to sink.

Phloem vessels still have cross walls called sieve plates that contain pores.

Companion cells actively load sucrose into the phloem.

Water follows high solute in phloem by osmosis. A positive pressure potential develops moving mass of phloem sap forward.

Phloem still contains small amount of cytoplasm along the walls but the organelle content is greatly reduced.

Companion cells actively unload (ATP used) the organic molecules

Question 18

mineral requirements of plants

Answer 18

• nitrogen

- magnesium

Question 19

nitrogen purpose for plants

Answer 19

Needed for protein synthesis `

Deficiency: small plant, slow growth, top leaves pale, bottom leaves dead and roots slightly affected

Question 20

magnesium purpose for plants

Answer 20

Needed for chlorophyll synthesis

Deficiency: plant lack chlorophyll, leaves yellow but normal roots

Question 21

what are nitrogen fertilizers

Answer 21

provide nitrogen in the form of nitrate ions, nitrite ions or ammonium ions. But using fertilisers can lead to eutrophication, which is when the fertiliser is transported by rain and leaches into stagnant water e.g. pond or river