Plant Transport Flashcards
Why do plants require specialised transport systems (3 reasons)
They have a low surface area to volume ratio
They are multicellular
They have a high metabolic rate
Because of these 3 reasons what can’t plants rely on
They can’t rely on diffusion alone for the transport of molecules, as it wouldn’t meet the metabolic rate
What can the green parts of plants do and what do the products do
They can carry of photosynthesis producing oxygen and glucose.
The glucose and oxygen can then be used in aerobic respiration.
What is a feature of certain parts of a plant and as a result what has to be transported to them.
Because many parts of multicellular plants can’t carry out photosynthesis the sugars must be transported to these tissues.
What are cotyledons
They are organs that act as food stores for developing embryo plants and form the first leaves when the seed germinates
What are the two types of plants
Monocotyledons which contain one cotyledons
Dicotyledons which contain two cotyledons
What is a difference between monocotyledons and dicotyledons
The transport systems in the two plants are arranged differently
What are herbaceos dicotyledons
They have a soft tissue and a relatively short lifecycle
What are woody dicots
They are dicots with hard, lignified tissues and long life cycles.
What doesn’t need a transport systems in plants and why
The demand for oxygen can be met by diffusion across the stomata as the leaves have adapted to have a large surface area
What needs a transport system in plants and why
The demand for water, minerals and sugars in large plants requires transport systems.
What are the two different transport systems in plants
The xylem and the phloem
What does the xylem carry
It carries water and mineral ions from the roots of the plant up the stem to the leaves
What does the phloem carry
It transports organic molecules such as sugars produced by photosynthesis in the leaves.
In what direction do the assimilates move in the phloem
These molecules move in the phloem down the plant to the roots or up the plant to the flowers
Where are xylem and phloem vessels found
They are grouped together in vascular bundles and the arrangement of the vascular bundles is different in the roots, stem and the leaves.
What does the vascular bundles look like in the stem
DRAW IT
What is the cortex
It is a thick layer of cells and contains parenchyma cells which are found in plants
What is a feature of xylem vessels
They are mechanically strong as they are grouped together in the centre of the root, helping to prevent the plant from being pulled out the soil by strong winds
How are the vascular bundles arranged in the stem
They are arranged in a ring around the edge of the stem
Draw what the structure of the vascular bundles in the stem looks like
DRAW IT
What is the purpose of the Sclerenchyma and features of it
.Support and structure
.It is thickened with lignin and cellulose
.Strengthens the stem and leaf midribs
What is the purpose of the Collenchyma and features of it
Found in the epidermis and involved in growth
Thick cellulose walls, giving strength to vascular bundles and other parts of stems
Flexible providing wind resistance
What is the purpose of the Parenchyma and features of it
A soft packing tissue which fills spaces between other tissues
In roots, parenchyma cells may store starach
In leaves some have chloroplasts
In aquatic plants some parenchyma have air spaces to keep the plant buoyant
What is different about the structure of the vascular bundles in woody plants
In woody plants the bundles are separate in young stems but form a continuous ring in older stems. So the vascular bundles is a complete ring of tissue just under the bark.
What is the purpose of the continuous rings of vascular bundles in woody plants
It provides strength and flexibility to withstand the bending forces to which stems and branches are exposed to
What is in between the xylem and phloem and what does it do
A layer of cambium, which contains meristem cells that divide to form new xylem and phloem
What is the pith
The centre of the plant stem that consists of parenchyma cells which
Where are the vascular bundles in stems found
They are around the edge of the stem and the xylem vessels are found closer to the centre than the phloem vessels.
What is the second purpose of the vascular bundles being around the edge of the cells
It allows the stem to withstand bending due to wind.
What is the structure of the vascular bundles being in leaves
DRAW IT
What is the upper part and lower part of the vascular bundles in a leaf
The upper part is the xylem and the lower part is the phloem
What also supports the leaf
It is also supported by other smaller vascular bundles that surround the main one
Where does photosynthesis take place in the leaf
In the palisade mesophyll
What does xylem consist of
Two main types of tissue called xylem vessels and xylem fibres.
How are the xylem vessels formed
They start as a series of plant cells running up the stem from the roots to the leaves
At a certain point the carbohydrate lignin forms within the cell walls
Lignin is impermeable and prevents substances from passing through the cell wall.
The living contents of the cells die and the end walls between cells break down.
What are bordered pits and what do they do
Regions of the cell walls remain free of lignin and are called bordered pits, they allow water and dissolved substances to pass between vessels. They also allow water to move out of the xylem for example to cells in the leaves.
What do the xylem vessels consist of after development and what do they do
It consists of non living hollow tubes, and the function is to carry water and dissolved mineral ions up the plant from the roots to the leaves.
What happens if a xylem vessel is blocked or damaged
The water can move through the bordered pits to different vessels.
How can lignin be arranged
In spirals or rings
It can also be continuous apart from the pits
What does the lignin do
The lignin helps to support the structure of the xylem vessels as when water is pulled up the xylem vessels the pressure falls slightly and the lignin helps to prevent the vessel from collapsing.
What are the 3 different types of arrangement of lignin in the xylem
Spiral
Annular (rings)
Reticulate (broken rings)
What are xylem fibres formed from
Long narrow cells that have very large amounts of lignin in them, the interior contents of the cells die.
What are the xylem fibres used for
They aren’t used to transport water and instead provide mechanical support for the planet
What can the parenchyma in the xylem do
Act as a store of starch
They also contain bitter compounds called tannins deterring herbivores from eating the plant.
What occurs in the leaves of a plant and what is the product used for and what are what they are used for called
The plant carries out photosynthesis producing the sugar glucose. The glucose is used to form other compounds such as different sugars and amino acids. These compounds are called assimilates.
What is the job of the phloem
To transport the assimilates to other parts of the plant such as the roots or flowers. Meaning molecules can be transported up and down the phloem.
What is the fluid moving in the phloem called
Phloem sap
what is a difference between xylem and phloem and how many types of tissue does the phloem consist of
The phloem is a living tissue
The phloem consists of 2 different types of tissue
What does a sieve tube element consist of
They consist of a long line of cells arranged end to end and inside all these cells almost all the organelles have been lost including the nucleus and vacuole. Leaving the interior almost entirely free to transport phloem sap.
What is a feature of the end walls of the sieve tube elements. And what do they allow
They have been modified to contain large pores and are called sieve plates
And they allow the phloem sap to move between cells
Because the sieve tubes elements have lost most of their organelles what can’t they do and as a result what is the solution
They can’t produce large amounts of essential molecules such as ATP. So next to the sieve tube element cells are companion cells which contain a nucleus and large amounts of mitochondria.
What links the sieve tube element to the companion cells and what do they do
Microscopic channels link the companion cells to the sieve tube elements called plasmosdesmata. And molecules such as ATP and proteins can move through them into the sieve tube element cells.
What is the role of companion cells
To provide essential molecules to the sieve tube element cells.
What do the phloem tubes not contain in their walls and what do they have instead to provide support
They don’t contain lignin in their walls
They have 2 different types of tissue to provide support called fibres and sclereids (both of which have thickened cell walls containing lignin)
What is the difference between fibres and sclereids
The fibres are long and narrow whereas the sclereids have a variety of shapes
