Transpiration And Translocation Flashcards
what is transpiration
the evaporation of water from plants
where is water carried thorough in a plant
in the xylem tube which are vessels from the roots to leaves
what are the features or adaptations of xylem tubes
- thick side walls and rings of lignin
- dead cells have no cytoplasm
- lack of cell walls between cells
- tiny pores
what does the lignin do
keeps it strong
what are the features or adaptations of phloem tubes
- holes in ends of cell walls
- pores
- very small amount of cytoplasm
how does transpiration happen
- water travels up xylem tubes like a suction system
- water travels to leaves
- unbroken chain of water molecules held together by weak forces of attraction between molecules
- as water from leaves evaporates, more is drawn into the roots
what factors impact the rate of trnaspiration
- light intensity
- temperature
- air flow or wind speed
why is water important for a plant (2)
- plants wilt as water sustains a plants structure. if little water, plant cant stand up properly
- it helps photosynthesis be done in its optimum conditions,like controlling temp of plant
how do you measure the rate of transpiration
- with a potometer
- it measures the movement of a bubble in a capillary tube
how does poor air flow affect the rate of transpiration
- if air flow if poor, water vapour just surrounds leaf and doesnt move away
- this means that there is a high concentration of water particles outside the leaf as well as inside
- so diffusion doesnt happen quickly
how does light intensity affect the rate of transpiration
- the brighter the light, the greater the transpiration rate
- stomata begin to close as it gets darker
- as photosynthesis cant happen in the dark, so stomata dont need to be open to absorb CO2
- when stomata are closed, very little water can escape
what is translocation
the movement of sugars in a plant
what happens in translocation
- plants make sucrose from glucose after photosynthesis
- its transported via translocation in the sieve tubes in the phloem
- companion cells actively pump sucrose into and out of the sieve tubes
what are xylem tubes made up of
dead cells joined end to end with no walls between them and a hole in the middle
what is the transpiration stream
the movement of water from the roots, through the xylem and out of the leaves
what is a phloem tube made up of
columns of elongated living cells with small pores in the end walls to allow stuff to flow through
what is the function of the phloem tube
to transport food substances (mainly sucrose) made in the leaves to the rest of the plant for immediate use or for storage
what does translocation require
- energy from respiration
- as the transport goes in both directions
how does good air flow or quick wind speeds affect the rat of transpiration
- if there is good air flow, rate of transpiration increases
- because the water is swept away
- which maintains a low concentration of water particles in the air outside the leaf
- so diffusion from the leaves happens quickly, from an area of high concentration to an area of low concentration
how does temperature affect the rate of transpiration
- the warmer it is, the faster transpiration happens
- when its warm the water particles have more energy
- to evaporate and diffuse out of the stomata
how do you measure the rate of transpiration suing a potometer
distance moved / time taken
what is water uptake by the plant directly related to
- water loss from the leaves
- as the xylem tube is a continuously flowing source of water
why do xylem tubes have thick walls and rings of lignin
- to form rigid tubes that wont burst or collapse
- and provide support
why do xylem tubes have dead cells with no cytoplasm
to form an empty tube for water to flow through
why do xylem tubes lack cell walls between cells
so that water flow is not slowed down
why do xylem tubes have tiny pores in cells
to allow water to enter and leave xylem vessels
why do phloem tubes have holes in the end of cell walls
to allow liquids and minerals to flow from one sieve cell to next
why do phloem tubes have pores
to have holes which sucrose solution can be pumped through
why do phloem tubes have small amounts of cytoplasm
so there is more room for the central channel
