factors affecting transpiration Flashcards
how can the rate of transpiration be measured?
-using a potometer
what are the three internal factor that affect the rate of transpiration?
-stomatal density
-leaf surface area
-cuticle thickness
what are the five external factor that affect the rate of transpiration?
-light intensity
-wind speed
-temp
-humidity
-soil water availability
the more stomata per unit area…
-the more evaporation and transpiration
the grater the leaf surface area…
-the more evaporation and transpiration
the thicker the cuticle…
-the less water is lost by evaporation and transpiration
during the day the rate of evaporation and transpiration…
-will be greater than the night due to the stomata closing at night
increasing wind speed will…
-increase the rate of evaporation and transpiration because it blows humid air away from the leaf
what does strong wind maintain in a leaf?
-a steep water potential gradient between the inside and outside of the leaf which allows water the evaporate quickly
the higher the temperature…
-the greater the rate of evaporation and transpiration
increasing the humidity will…
-decrease the rate of evaporation and transpiration because the water potential gradient decreases between the inside and outside of the leaf
in very dry soil conditions …
-the rate of evaporation and transpiration will decrease due to a lack of water in the soil
what is translocation?
-the movement of organic solutes mainly sucrose within the phloem
what two things does the movement of sucrose require?
-energy expenditure
-a two way movement by mass flow transport
what are 2 things in the phloem that shows a two way system is being carried out?
-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
what stops mass flow of sucrose?
-metabolic inhibitors e.g. potassium cyanide which stops respiration and disrupts translocation
how does mass flow move the sucrose in the phloem ?
-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
what is evidence for the two way flow system?
-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
why are the phloem walls not lignified?
-they are not under pressure
