The leaf - 2

Question 1

Suggest how the guard cells control the stomata. (2)

Answer 1

*Absorbs and loses water to open and close the stomata

Question 2

State each leaf layer and explain how it helps in photosynthesis. (6) give 8 points

Answer 2

*waxy cuticle
*reduces water loss
*upper epidermis
*thin/transparent allows light to enter palisade
*Palisade mesophyll
*contains many chloroplasts for P.S
*Spongy mesophyll layer
*air spaces, increases SA for diffusion
*lower epidermis
*contains guard cells (controls water loss) + stomata (diffusion)
*vascular bundle
*contains xylem and phloem

Question 3

Describe and explain how the structure of the whole leaf is adapted for photosynthesis. (4)

Answer 3

*flat
*large SA - diffusion
*thin
* short diffusion pathway

Question 4

State what the deficiency of magnesium does to a plant. (1)

Answer 4

*yellow leaves (chlorosis)

Question 5

State what the deficiency of nitrates does to plant. (1)

Answer 5

*stunted growth
*yellow leaves

Question 6

State what the deficiency of phosphates does to plant. (1)

Answer 6

*purple leaves

Question 7

State the role of xylem. (2)

Answer 7

*transport water and mineral ions
*from roots to shoots

Question 8

State role of phloem. (2)

Answer 8

*carry products of photosynthesis (sucrose and a.a)
*all parts of plants up and down

Question 9

Explain how the xylem is adapted for its function. (4)

Answer 9

*contain rings of lignin
*waterproof, water wont leak + structural support
* Hollow, dead cells
*form tubes so water can pass

Question 10

Explain how phloem is adapted for its function. (4)

Answer 10

*companion cells
*provide energy for sieve cells and A.T of sucrose
*sieve cells
*allows movement of substances
*pores
*enable movement of cell sap

Question 11

State what is meant by the term translocation. (2)

Answer 11

*movement of food substances (sugars)
*around the plant

Question 12

Explain how a root hair cell carries out its function (taking up water). (3)

Answer 12

*mineral ions are taken up by active transport
*water potential inside cell decreases
*water enters through osmosis

Question 13

Suggest why the phloem transports substances both ways. (2)

Answer 13

*to take sucrose to root hair cells
*so they can respire aerobically

Question 14

State what is meant by the term transpiration. (2)

Answer 14

*evaporation of water
*at surface of a plant

Question 15

State the 4 different factors that affect the rate of transpiration. (4)

Answer 15

*temperature
*humidity
*wind speed
*light intensity

Question 16

Explain how high temperature affects transpiration. (3)

Answer 16

*Water molecules have higher Kinetic energy
*they move faster
*evaporation happening at faster rate
*therefore high rate of transpiration

Question 17

Explain how an increase in light intensity affects transpiration. (3)

Answer 17

*more photosynthesis
*more stomata opened for co2
*more water can evaporate
*so more transpiration

Question 18

Explain how an increase in wind speed affects transpiration. (3)

Answer 18

*more water blown from surface of leaf
*conc. of water vapour around leaf is lower
*steeper conc. gradient
*higher rate of transpiration

Question 19

Explain how an increase in humidity will affect rate of transpiration. (3)

Answer 19

*reduced concentration gradient between conc. of w.v inside and outside
*slower rate of diffusion
*decrease in transpiration

Question 20

State three ways transpiration is useful for plants. (3)

Answer 20

*keeps plant cool as heat energy is lost when water evaporates
*keeps plant straight as cells are turgid
*provides water for photosynthesis

Question 21

Describe how the green pigment in leaf cells is removed safely before testing
a leaf for the presence of starch. (3)

Answer 21

*boil in ethanol
*ensure no naked flame
*or use water bath

Question 22

Explain why light intensity changes the mean volume of water lost by the shoot. (2)

Answer 22

*more water loss at high intensity
*as more stomata open
*remains constant as all stomata are opened