factors affecting transpiration Flashcards

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1
Q

how can the rate of transpiration be measured?

A

-using a potometer

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2
Q

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

A

-stomatal density
-leaf surface area
-cuticle thickness

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3
Q

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

A

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

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4
Q

the more stomata per unit area…

A

-the more evaporation and transpiration

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5
Q

the grater the leaf surface area…

A

-the more evaporation and transpiration

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6
Q

the thicker the cuticle…

A

-the less water is lost by evaporation and transpiration

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7
Q

during the day the rate of evaporation and transpiration…

A

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

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8
Q

increasing wind speed will…

A

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

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9
Q

what does strong wind maintain in a leaf?

A

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

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10
Q

the higher the temperature…

A

-the greater the rate of evaporation and transpiration

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11
Q

increasing the humidity will…

A

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

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12
Q

in very dry soil conditions …

A

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

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13
Q

what is translocation?

A

-the movement of organic solutes mainly sucrose within the phloem

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14
Q

what two things does the movement of sucrose require?

A

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

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15
Q

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

A

-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

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16
Q

what stops mass flow of sucrose?

A

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

17
Q

how does mass flow move the sucrose in the phloem ?

A

-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

18
Q

what is evidence for the two way flow system?

A

-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

19
Q

why are the phloem walls not lignified?

A

-they are not under pressure