B2 - transpiration

Question 1

Transpiration stream process (4)

Answer 1

1. Transpiration starts with the evaporation of water from cells inside the leaf
2. the water vapour then diffuses through the air spaces in the spongy mesophyll and out of the leaf through the stomata
3. water passes from the xylem into the leaf to replace the water that has been lost
4. water is drawn into the root hair cells and up the xylem vessels to the leaf

Question 2

what does transpiration do?

Answer 2

• brings water into leaf which is needed for photosynthesis
• transports dissolved mineral ions such as magnesium which is used for chlorophyll
• evaporation of water cools the leaf down

Question 3

what is translocation?

Answer 3

how plant transport sugars made by photosynthesis to the rest of the plant to be used for energy.

Question 4

how are sugars transported in translocation?

Answer 4

phloem cell have long column called phloem tubes.
They have pored which allow the movement of sap

Question 5

what direction does substances move in phloem cells?

Answer 5

both directions - up and down

Question 6

what is cell sap?

Answer 6

a mixture of sugar and water

Question 7

upper epidermis is…
- covered…
reduces…
prevents

Answer 7

is thin and transparent so allows light pass through to the palisade layers
- covered with thin layer of oily material (waxy cuticle) —> reduces evaportaion of water from the surface of the leaf –> prevents the leaf from drying out

Question 8

what does that lower epidermis consists of?

Answer 8

has tiny pores called the stomata

Question 9

Stomata
- helps …
- allows…
- has..
- At night ..
- In the day..

Answer 9

• helps control amount of water vapour that can pass out of the leaf
• allows CO2 enter and oxygen to leave
• has guard cells on either side
• At night they lose water by osmosis and and become flaccid, this closes the stomata and prevents transpiration when the plant is not photosynthesising
• In the day, the guard cells gain water by osmosis and become turgid, this openes the stomata allowing gas exchange to happens

Question 10

what is the spongy mesophyll full of?
- allows… through.. to…

Answer 10

full of air spaces —> allows CO2 needed for photosynthesis to diffuse from the stomata through the spongy mesophyll to the palisade cells and oxygen produced from photosynthesis out of the cells and into the airspaces and diffuse out of the leaf through the stomata

Question 11

what are guard cells adapted for?

Answer 11

are adapted to open and close the stomata

Question 12

Phloem tissues transport…
these…

Answer 12

transport dissolved sugars produced by photosynthesis
- these sugars can be stored as starch or used immediately e.g glucose on respiration

Question 13

Xylem tissues transport…
some…
2. transports…
e.g…

Answer 13

1.transport water from the roots to the stem and the leaves
- some of this water is used in photosynthesis
2.transports dissolved mineral ions
(e.g magnesium which is used for chlorophyll)

Question 14

palisade mesophyll tissues contain…
which are…
which…

Answer 14

contain palisade cells —> which are packed of chloroplasts —> which absorb light energy needed for photosynthesis.
- are towards top of leaf so can absorb as much light intensity as possible

Question 15

where are meristem tissues found and what do they contain?

Answer 15

• found in growing tips (e.g shoots and roots)
• contain stem cells —> that can differentiate into different types of plant tissues

Question 16

PRACTICAL: investigating transpiration

Answer 16

1. take 3 leaves from same plant
2. record mass of each leaf
3. prepare them:
   Leaf 1: cover upper surface in vaseline
   Leaf 2: cover lower surface in vaseline
   Leaf 3: don’t cover with vaseline
4. hang leaves in classroom for 3 days
5. record mass —> calculate difference in mass

Question 17

how does light intensity affect rate of transpiration?

Answer 17

increase light intensity –> higher rate —> stomata opens wider allowing more CO2 into leaf for photosynthesis —> more water cam evaporate –> so higher rate

Question 18

how does humidity affect the rate of transpiration?

Answer 18

increased humidity–> decreased rate —> bcus moist air surrounds stomata —> decreases rate of evaporation —> less water lost from plant

Question 19

how does wind speed affect the rate of transpiration?

Answer 19

increased wind speed —> higher rate –>bcus wind removes more water vapour from surface of stomata—> increases rate of evaporation from stomata —> so more water is lost from the plant

Question 20

how does temperature affect the rate of transpiration?

Answer 20

increased temp —> higher rate —> bcus particles have more energy —> increased rate of evaporation —> more water is lost

Question 21

describe the process of transpiration in plants.

Answer 21

evaporation of water mostly from the leaf through the stomata causing a pull so that water moves up through the plant as the transpiration stream, water enters through roots and up the plant