Section 3: Plant nutrition and transport

Question 1

chloroplasts contain a pigment called…

Answer 1

chlorophyll

Question 2

what is the word equation for photosynthesis?

Answer 2

carbon dioxide + water –> glucose + oxygen

Question 3

what is the symbol equation for photosynthesis?

Answer 3

6CO2 + 6H2O –> C6H12O6 + 6O2

Question 4

what is the top layer of the leaf called?

Answer 4

waxy cuticle

Question 5

name 5 parts of a typical leaf

Answer 5

upper/lower epidermis, palisade mesophyll layer, spongy mesophyll layer, vascular bundle, stomata, guard cells

Question 6

in which layer are most of the leaf’s chloroplasts found and why?

Answer 6

the palisade layer, so that they get the most light, being near the top of the leaf

Question 7

what do the vascular bundles of the leaf contain?

Answer 7

xylem and phloem: the transport vessels

Question 8

what is the role of the waxy cuticle?

Answer 8

reduces water loss by evaporation

Question 9

how is the upper epidermis adapted for optimum photosynthesis?

Answer 9

transparent - so that light can pass through it to the palisade layer

Question 10

where in the leaf are most of the chloroplasts found?

Answer 10

in the palisade layer

Question 11

what happens to the rate of photosynthesis when the temperature increases?

Answer 11

the rate of photosynthesis increases up to a point - eventually the plant’s enzymes denature so the rate of photosynthesis rapidly decreases

Question 12

how to test a leaf for starch?

Answer 12

1. kill the leaf by soaking it in boiling water - to stop any chemical reactions happening inside the leaf
2. put the leaf in a boiling tube with some ethanol and heat the tube in a water bath - to get rid of any chlorophyll - the leaf should end up pale white in colour
3. rinse the leaf in cold water
4. add a few drops of iodine solution - if starch is present in the leaf it will turn blue-black

Question 13

how to show that chlorophyll is needed for photosynthesis using a variegated leaf?

Answer 13

1. take a variegated leaf from a plant that’s been exposed to light
2. test the leaf for starch using the method - only the green bits will turn blue-black, the white bis will stay brown in colour like the iodine
3. this suggests that only the parts of the leaf that contain chlorophyll are able to photosynthesise and produce starch
   CONTROL: TEMP, CO2, WATER, LIGHT

Question 14

how to show that CO2 is needed for photosynthesis?

Answer 14

1. put a plant in a sealed bell jar with light shining on it and some soda lime in the jar too
2. the soda lime will absorb CO2 out of the air
3. leave plant in the jar for a while and then test a leaf for starch - it won’t turn blue-back, showing that CO2 is needed for the plant to photosynthesise and make starch
   CONTROL: LIGHT, TEMP, WATER

Question 15

how to show that light is needed for photosynthesis?

Answer 15

1. grow a plant without any life
2. cut a leaf from the plant and test it for starch using iodine solution - the leaf will not turn blue-black, showing that light is needed for photosynthesis to occur and starch to be made``
   CONTROL: LEVELS OFCO2, TEMP, WATER

Question 16

how to use Canadian pondweed to measure the effect of light intensity on the rate of photosynthesis? (oxygen levels correspond to the rate of photosynthesis)

Answer 16

1. a source of white light is placed at a specific distance from the pondweed
2. the pondweed is left to photosynthesise for a set amount of time - as it photosynthesises the oxygen will collect in the capillary tube
3. at the end of the experiment the syringe is used to draw the gas bubble in the tube up alongside a ruler and the length of the gas bubble is measured. This is proportional to the volume of O2 produced
4. repeat experiment with the light source placed at different distances from the pondweed
   CONTROL: TIME, TEMP.

Question 17

why do plants need nitrates? what does a deficiency cause?

Answer 17

contain nitrogen for making amino acids and proteins needed for cell growth. A lack of nitrates leads to stunted growth and yellow older leaves

Question 18

why do plants need phosphates? what does a deficiency cause?

Answer 18

contain phosphorus for making DNA and cell membranes, needed for respiration and growth. A lack of phosphates leads to poor root growth and purple older leaves

Question 19

why do plants need potassium? what does a deficiency cause?

Answer 19

to help the enzymes needed for photosynthesis and respiration. A lack of potassium in the soil leads to poor flower and fruit growth and discoloured leaves

Question 20

what kind of amounts of magnesium do plants need? why? what does a deficiency cause?

Answer 20

fairly small amounts. Needed for making chlorophyll for photosynthesis. Lack of magnesium causes yellow leaves

Question 21

why do multicellular organisms need transport systems? how do unicellular organisms absorb/release substances?

Answer 21

to move substances to and from individual cells. Unicellular - substances can diffuse directly into and out of the cell across the cell membrane.

Question 22

what is the role of the xylem? they transport from where to where?

Answer 22

carry water and mineral salts from the roots up to the shoots in the transpiration stream