factors affecting transpiration

Question 1

how can the rate of transpiration be measured?

Answer 1

-using a potometer

Question 2

what are the three internal factor that affect the rate of transpiration?

Answer 2

-stomatal density
-leaf surface area
-cuticle thickness

Question 3

what are the five external factor that affect the rate of transpiration?

Answer 3

-light intensity
-wind speed
-temp
-humidity
-soil water availability

Question 4

the more stomata per unit area…

Answer 4

-the more evaporation and transpiration

Question 5

the grater the leaf surface area…

Answer 5

-the more evaporation and transpiration

Question 6

the thicker the cuticle…

Answer 6

-the less water is lost by evaporation and transpiration

Question 7

during the day the rate of evaporation and transpiration…

Answer 7

-will be greater than the night due to the stomata closing at night

Question 8

increasing wind speed will…

Answer 8

-increase the rate of evaporation and transpiration because it blows humid air away from the leaf

Question 9

what does strong wind maintain in a leaf?

Answer 9

-a steep water potential gradient between the inside and outside of the leaf which allows water the evaporate quickly

Question 10

the higher the temperature…

Answer 10

-the greater the rate of evaporation and transpiration

Question 11

increasing the humidity will…

Answer 11

-decrease the rate of evaporation and transpiration because the water potential gradient decreases between the inside and outside of the leaf

Question 12

in very dry soil conditions …

Answer 12

-the rate of evaporation and transpiration will decrease due to a lack of water in the soil

Question 13

what is translocation?

Answer 13

-the movement of organic solutes mainly sucrose within the phloem

Question 14

what two things does the movement of sucrose require?

Answer 14

-energy expenditure
-a two way movement by mass flow transport

Question 15

what are 2 things in the phloem that shows a two way system is being carried out?

Answer 15

-rate of flow is higher than can be accounted for by diffusion
-companion cells have a high density of mitochondria which produce ATP energy which pump sucrose into sieve tube elements via the plasmodesmata

Question 16

what stops mass flow of sucrose?

Answer 16

-metabolic inhibitors e.g. potassium cyanide which stops respiration and disrupts translocation

Question 17

how does mass flow move the sucrose in the phloem ?

Answer 17

-mass flow occurs from source to sink
-the source is the organ where sugar is produced in photosynthesis e.g. the leaves
-the sink is the organ that consumes or stores the sucrose e.g. developing buds or the roots
-the build up of sucrose helps create a hydrostatic gradient between where the sucrose levels are lower e.g. the roots

Question 18

what is evidence for the two way flow system?

Answer 18

-this comes from the use of radioactively labelled sucrose, following the supply of labelled sucrose to the leaf radioactivity is detected in the shoots and tips

Question 19

why are the phloem walls not lignified?

Answer 19

-they are not under pressure