Chapter Note: Transport in plants | Biology for GCSE/IGCSE - Year 11 PDF Download

 Page 1


Transport in plants
? The transport system that carries water is made up of a tissue called xylem
? The transport system that carries water is made up of a tissue called phloem
? Xylem
? It is made of many dead and hollow cells joined end to end. No end walls
? It contains no cytoplasm or nuclei.
? Its walls are made up of cellulose and lignin, it helps keep the xylem upright
? Phloem
? Still have end walls, it has formed into sieve plates which have small holes in them.
? Phloem transports sucrose and amino acids from the leaves to roots and flowers.
? The cells are known as sieve tube elements, they contain cytoplasm but no nucleus and also
contain many other organelles
? They don't have lignin in their cell walls
? Sieve tube element’s companion cell has nucleus and many other organelles, it provides sieve
tube elements with some of their requirements
? Vascular bundles
? A group of xylem vessels and phloem tubes is
called a vascular bundle
? In the root, its found in the centre while in the
shoot, they are arranged in a ring near the outside
edge
? Water uptake
? Root cap is a layer of cells that protects the roots as it grows through the soil. They are present
at the tip of the end of the root.
? The rest of the root is covered by layer of cells called epidermis
? Water moves into a root hair by osmosis
¦ The water in the soil is normally a more dilute solution therefore water diffuses into the
root hair, down its concentration gradient through the partially permeable membrane.
? The pressure at the top is lowered and the pressure at the bottom stays high therefore water
flows up , the pressure is lowered through transpiration
Page 2


Transport in plants
? The transport system that carries water is made up of a tissue called xylem
? The transport system that carries water is made up of a tissue called phloem
? Xylem
? It is made of many dead and hollow cells joined end to end. No end walls
? It contains no cytoplasm or nuclei.
? Its walls are made up of cellulose and lignin, it helps keep the xylem upright
? Phloem
? Still have end walls, it has formed into sieve plates which have small holes in them.
? Phloem transports sucrose and amino acids from the leaves to roots and flowers.
? The cells are known as sieve tube elements, they contain cytoplasm but no nucleus and also
contain many other organelles
? They don't have lignin in their cell walls
? Sieve tube element’s companion cell has nucleus and many other organelles, it provides sieve
tube elements with some of their requirements
? Vascular bundles
? A group of xylem vessels and phloem tubes is
called a vascular bundle
? In the root, its found in the centre while in the
shoot, they are arranged in a ring near the outside
edge
? Water uptake
? Root cap is a layer of cells that protects the roots as it grows through the soil. They are present
at the tip of the end of the root.
? The rest of the root is covered by layer of cells called epidermis
? Water moves into a root hair by osmosis
¦ The water in the soil is normally a more dilute solution therefore water diffuses into the
root hair, down its concentration gradient through the partially permeable membrane.
? The pressure at the top is lowered and the pressure at the bottom stays high therefore water
flows up , the pressure is lowered through transpiration
? Transpiration
? It is the evaporation of water from a plant. It mostly takes place from the leaves.
? The mesophyll cells inside the leaf are each covered with a thin layer of moisture, some of this
moisture evaporates from the cells, water  vapour diffuses out of the leaf through the stomata.
Water from the xylem vessels in the leaf travel to replace it. This constant process reduces the
effective pressure at the top of the xylem vessels letting the water flow up.
? This process is known as transpiration stream
? Cohesion
? Water molecules have a strong tendency to stick together, this is called cohesion
? When the water is pulled up the xylem vessels, the whole column of water stays together.
? Without cohesion the water column would break apart and the whole system would not work.
? The structure of the plant is adapted to help it take up water and move it up throughout the plant
? The root hair cells provide a huge surface area through which water can be absorbed. THis
increases the quantity of water that can move into the plant at any moment.
? THe hollow, narrow  xylem vessels provide an easy pathway for water to flow all the wat up from
the roots to the very top of the plant
? The many air spaces inside the lead mean that there is a large surface area of wet cells from
which water can evaporate into the air. This increases the rate of evaporation, drawing more
water out of the xylem
? The stomata, when open, allow water vapour to diffuse easily out of the lead. This reduces the
water potential inside the lead, which encourages more water to evaporate from the surfaces of
the mesophyll cells
? A potometer is used to measure the transpiration rate of plants
Conditions that affect transpiration rate
? Temperature
? On hotter days, water will evaporate more quickly, they are directly proportional.
? Humidity
? The higher humidity, the less water will evaporate from the leaves, because there is not much of
a diffusion gradient for the water between the air spaces inside and lead and the wet air around
it. They are inversely proportional
? Wind speed
? Transpiration rate increases as wind speed increases. They are directly proportional
? Light intensity
? Directly proportional
? Water supply
? Directly proportional, less water supply, less water to transpire
? Translocation
? The movement of sucrose and amino acids in phloem, from regions of production to regions or
storage or regions or utilisation in respiration or growth.
? Sources
? The part of the plant from which sucrose and amino acids are being translocated is a source
Page 3


Transport in plants
? The transport system that carries water is made up of a tissue called xylem
? The transport system that carries water is made up of a tissue called phloem
? Xylem
? It is made of many dead and hollow cells joined end to end. No end walls
? It contains no cytoplasm or nuclei.
? Its walls are made up of cellulose and lignin, it helps keep the xylem upright
? Phloem
? Still have end walls, it has formed into sieve plates which have small holes in them.
? Phloem transports sucrose and amino acids from the leaves to roots and flowers.
? The cells are known as sieve tube elements, they contain cytoplasm but no nucleus and also
contain many other organelles
? They don't have lignin in their cell walls
? Sieve tube element’s companion cell has nucleus and many other organelles, it provides sieve
tube elements with some of their requirements
? Vascular bundles
? A group of xylem vessels and phloem tubes is
called a vascular bundle
? In the root, its found in the centre while in the
shoot, they are arranged in a ring near the outside
edge
? Water uptake
? Root cap is a layer of cells that protects the roots as it grows through the soil. They are present
at the tip of the end of the root.
? The rest of the root is covered by layer of cells called epidermis
? Water moves into a root hair by osmosis
¦ The water in the soil is normally a more dilute solution therefore water diffuses into the
root hair, down its concentration gradient through the partially permeable membrane.
? The pressure at the top is lowered and the pressure at the bottom stays high therefore water
flows up , the pressure is lowered through transpiration
? Transpiration
? It is the evaporation of water from a plant. It mostly takes place from the leaves.
? The mesophyll cells inside the leaf are each covered with a thin layer of moisture, some of this
moisture evaporates from the cells, water  vapour diffuses out of the leaf through the stomata.
Water from the xylem vessels in the leaf travel to replace it. This constant process reduces the
effective pressure at the top of the xylem vessels letting the water flow up.
? This process is known as transpiration stream
? Cohesion
? Water molecules have a strong tendency to stick together, this is called cohesion
? When the water is pulled up the xylem vessels, the whole column of water stays together.
? Without cohesion the water column would break apart and the whole system would not work.
? The structure of the plant is adapted to help it take up water and move it up throughout the plant
? The root hair cells provide a huge surface area through which water can be absorbed. THis
increases the quantity of water that can move into the plant at any moment.
? THe hollow, narrow  xylem vessels provide an easy pathway for water to flow all the wat up from
the roots to the very top of the plant
? The many air spaces inside the lead mean that there is a large surface area of wet cells from
which water can evaporate into the air. This increases the rate of evaporation, drawing more
water out of the xylem
? The stomata, when open, allow water vapour to diffuse easily out of the lead. This reduces the
water potential inside the lead, which encourages more water to evaporate from the surfaces of
the mesophyll cells
? A potometer is used to measure the transpiration rate of plants
Conditions that affect transpiration rate
? Temperature
? On hotter days, water will evaporate more quickly, they are directly proportional.
? Humidity
? The higher humidity, the less water will evaporate from the leaves, because there is not much of
a diffusion gradient for the water between the air spaces inside and lead and the wet air around
it. They are inversely proportional
? Wind speed
? Transpiration rate increases as wind speed increases. They are directly proportional
? Light intensity
? Directly proportional
? Water supply
? Directly proportional, less water supply, less water to transpire
? Translocation
? The movement of sucrose and amino acids in phloem, from regions of production to regions or
storage or regions or utilisation in respiration or growth.
? Sources
? The part of the plant from which sucrose and amino acids are being translocated is a source
? Sink
? The part of the plant to which sucrose and amino acids are being translocated is a sink
? Include the roots and flowers