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60 Cards in this Set

  • Front
  • Back
How do exchange of substances in an organism take place?
Passive and active transport
If the rate of transport is effective and rapid, what does this tell you about the distance?
Short distance
In what case there is no need for a special transport system?
When an unicellular and multi-cellular organism has large surface are to volume ration
When will specialized long distance transport systems which can move substances more rapidly become necessary?
when it is larger, active and complex organisms
What are plant cells requirements in order to survive?
1.CO2 (Diffuse into and out of the cells)
2. O2 (Diffuse into and out of the cells)
3. Organic nutrient (non-photosynthetic cells need to be supplied with organic nutrients from photosynthetic cells)
4. Inorganic ions and water
5. Sunlight (for photosynthetic region of plants)
What are the 2 transport systems in plants?
1. Root system
2. Shoot system
Describe how the Root system works
Carry water and inorganic ions from roots to parts above the ground.
Describe how the Shoot system works
Carry substances made by photosynthesis from leaves to other areas.
Why the plant transport system does not carry oxygen and carbon dioxide?
This is because the gases travel to and from cells and their environment by diffusion alone.
What are the 3 types of simple plant tissues?
Describe the main function of the parenchyma cells
as packing tissue

When turgid, provide support in hebaceous plants

Metabolically active (site of many activities)

Intercellular air space allows gaseous exchange

Food storage e.g. potato tubers

Transport of water and mineral salts through cells or cell walls
What is the cell wall material of a parenchyma cell made of?
Cellulose, pectins and hemicelluloses
What is the shape of a Parenchyma cell like?
Roughly spherical to elongated
Where are the parenchyma cells found?
Cortex, pith, packing tissue in xylem or phloem
how are Collenchyma characterized?
Deposition of extra cellulose at the corners of cells
Describe the main function of the Collenchyma cells
Support and mechanical strength
What is the cell wall material of a Collenchyma cell made of?
Cellulose, pectins and hemicelluloses
What is the shape of a Collenchyma cell like?
Elongated and polygonal with tapering ends
Where are the Collenchyma cells found?
Below the epidermis, in the outer region of the cortex.
Sclenchyma Cells can be categorized into 2 types. What are they?
Fibres and Sclereids
What is the main function of a Fiber?
Strong support
What are the cell walls of fibers made of?
Lignin, cellulose, pectins and hemicelluloses
Describe the shape of a Fiber cell
Elongated and polygonal with tapering interlocking ends
Where are Fibers found?
Outer regions of cortex, pericycle of stem, xylem and phloem
What is the main function of a Sclereids?
Confer firmness or rigidity on structures
What are the cell walls of sclereids made of?
Lignin, cellulose, pectins and hemicelluloses
Describe the shape of a sclereids cell
Roughly spherical or irregular
Where are sclereids found?
cortex, pith, phloem, seeds, stones of fruits
What are the 3 different pathways in which water moves across the root?
Apoplast pathway
Symplast pathway
Vacuolar pathway
Describe Apoplast pathway
It is a system of adjacent cell walls which is continuous throughout the plant.

Spaces between cell walls are filled with water and the water moves through the cell walls

Cell walls are freely permeable so dissolved ions or molecules can move freely through them
Describe Symplast pathway
Is is a system of interconnected protoplasts whereby the neighboring cytoplasms of protoplasts are linked by plasmodesmata

Once taken into the cytoplasm, water or other solutions no longer have to cross any further membranes

Movement of the cytoplasm might be aided by cytoplasmic streaming
Describe Vacuolar pathway
This is where water moves from vacuole to vacuole through neighboring cells. it crosses the symplast and apoplast in the process.

The water molecules moves through the membranes and tonoplasts by osmosis
What is the order in which water is transported in a plant?
Soil, root hairs, xylem tissues, move upwards through the roots, stem, leaves
Describe the process of transport of water.
Water from the soil enters a plant through its root hairs and them moves across the root into the xylem tissue in the center. once inside the xylem vessels, the water moves upwards through the root to the stem, and from the stem into the leaves
Describe Root hairs
The root tip is covered by a tough protective root cap and is not permeable to water.

Root hairs are long and thin extension of epidermal cells

These reach into spaces between the soil particles from where they absorb water that coat every soil particle

Water moves into the root hairs by osmosis.
Does soil water have high or low water potential? why?
High water potential. This is because even if they contain some inorganic ions in solution, it is relatively dilute solution
Does cytoplasm and cell sap have high or low water potential? why?
Low water potential. This is because the have considerable quantities of inorganic ions and organic substances, such as proteins and sugars, dissolved in them
How does water enter the cytoplasm and vacuole of the root hair cell?
Water diffuses down the water potential gradient, through a partially permeable membrane
How do you increase the rate at which water can be absorbed into the plant?
Large umber of root hair will provide a very large surface area
How are minerals and ions absorbed into the root hairs?
Facilitated diffusion
What happens if a particular ion has high concentration outside the root hair?
It will move passively into the cell by facilitated diffusion
What kind of fungi are sometimes found in or on the root hair cells? what are their functions?
Mycorrhizas, they act like a mass of fine roots which absorb nutrients, especially phosphate and nitrate, from the soil and transport it into the plant. in return, these fungi receive organic nutrients from the plants.
Why do ions need to be taken up by active transport from the soil?
This is because ions required by the plant are relatively low in the soil so they need to be taken up against the concentration gradient by active transport which uses ATP.
How are water taken transported from root hairs to xylem?
Water taken up by root hairs crosses the cortex and enters the xylem in the centre of the root. it does this because the water potential inside the xylem vessel is lower than the water potential in the root hairs so water moves down this water potential gradient across the root.
What are the 3 possible routes for water to cross the cortex?
Apoplast, Symplast and Vacuolar
What section of the plant stops the water?
When water move through spaces in the cell wall, it reaches the endodermis. Its progress is barred by a thick, waterproof, waxy substance. what is this substance?
Waxy band of Suberin called the casparian strips. It i the impenetrable barrier to water in the walls in the endodermis cells.
What happens to the water once it is blocked by the endodermis cells?
They are forced to use the symplast and apoplast pathway.
What is the reason for plants having casparian strips?
This is because cell wall is freely permeable and cell membrane is partially permeable so by forcing the water to take the symplast and Vacuolar pathway, ii is forced to cross the cell membrane which will act as a filter to solutes and inorganic materials. This will allow the plant to control what inorganic ions pass into its xylem vessels
What happens as endodermal cells get older?
The suberin deposits become more extensive, except in certain cells called passage cells, through which water can pass freely
What happens when the water is across the endodermis cells?
The water continues to move down the water potential gradient across the pericycle and towards the xylem vessels
What is a Xylem tissue?
It is made up of vessel elements, tracheids, fibres and parenchyma cells.
What is the function of Xylem tissues?
It has a dual function serving as mechanical support and transport of water and inorganic ions
What is a xylem vessel made up of?
Many elongated vessel elements arranged end to end
Explain the process at which a Vessel element is formed
Each began as a normal plant cell then lignin is deposited at the cell wall. As it is built up around the cell, the living content of the cell dies and this will leave an empty space inside called the lumen.
What is lignin?
It is a strong substance which is impermeable to water
Why do the Xylem vessels have pits
This is because no lignin was deposited at the plasmodesmata.
What are Pits on a Xylem vessel?
They are not open pores; they crossed by permeable, unthickened cellulose cell wall
How does all the neighbouring cells join up together to form a xylem vessel?
The end walls of neighbouring vessel elements breakdown completely to form a continuous tube.
What usually rely on xylem vessels for their water transport?
Angiosperms (flowering plants)