IQ3- Module 2: Organisation Of LIcing Things Flashcards
what are transport systems?
Transport systems ensure that all cells are supplied with the nutrients and gases they require and the removal of wastes.
They form continuous closed tubular pathways through roots, stems and leaves
what do the transport systems in plants involve?
Transport systems ensure that all cells are supplied with the nutrients and gases they require and the removal of wastes.
They form continuous closed tubular pathways through roots, stems and leaves
what is the transport medium in plants?
Water is the transport medium in plants.
▪ Xylem – contains mineral ions (nitrates, phosphates, calcium, potassium)
▪ Phloem – contains sugars and organic substances
what is the xylem?
Xylem is specialised tissue for the transport of water and dissolved mineral ions from the roots through the stem to the leaves. The movement occurs in only one direction (upwards from roots) and is a passive process (no energy).
what is the transpiration-cohesion-tension theory
The current theory to explain the upward movement of water and minerals through the xylem.
Transpiration aids in movement of water and minerals to leaves and cools the plant down.
The main idea is the evaporation of water from the leaves through the stomata known as transpiration. This creates a suction pull of water up through the stem from the roots. The movement of this column of water up the stem due to the evaporative pull of transpiration is known as the transpiration stream.
what does the transpiration-cohesion-tension theory process involve?
The process involves:
The concentration of water vapour outside the leaf is lower than inside the leaf, leading to the diffusion of water vapour out of the leaf known as transpiration.
When water is lost from the airspaces within the leaf, it is replaced by water from the mesophyll cells.
Then the mesophyll cells replace their water from nearby xylem.
This creates tension on the water stream and draws more water up the stem from the roots.
This causes more water to move into the roots and then the xylem by osmosis.
what is the tct theory aided by?
The movement is aided by a number of factors: ▪ Root pressure
− once water and minerals ions have been absorbed into the roots they move across the root into the xylem
− small amount of root pressure results from the continual influx of more water and ions, forcing the solution already present in the xylem to move upwards
− this pressure is not sufficient to lift the water and ions very high
▪ Thickened lignin walls can withstand the tension created and offers little resistance to the flow of water
▪ Cohesion
− attractive force between the water molecules (they stick together with the positive and negative ends attracted)
− this forms a continuous column of water
▪ Adhesion
− two different molecules are
attracted to each other
− water molecules stick to the sides of the xylem walls (cellulose walls) cause water to rise up the sides
− combined cohesion and adhesion forces ensures the continuous column of water moves through the xylem in the stem
what is phloem?
Phloem is specialised tissue for the transport of sugars such as glucose and other organic substances from the leaves to all regions of the plant where they are either used or stored. The movement occurs in both directions and is an active process (requires energy).
what is the translocation: source-sink theory?
The current theory to explain the movement of the products of photosynthesis from the leaves to all parts of the plant through the phloem.
The main idea is after glucose has been produced in leaves by the process of photosynthesis, it is either stored as starch or converted to sucrose and distributed to all parts of the plant. The distribution process is called translocation.
Materials in phloem move from a high pressure region to a low pressure region.
The high pressure region is in close proximity to where the sucrose is produced, known as the source.
While the low pressure region is where the sucrose is required, known as the sink.
what does the source-sink theory process involve?
At the source (leaf) energy is required to pump sugar (sucrose) into the phloem via active transport, creating a high concentration.
This will draw in water by osmosis from the xylem to balance the concentration creating a high pressure region.
The substances move from a region of high to low pressure.
At the sink (any part of the plant) energy is required to remove sugar (sucrose) from the phloem via active transport, creating a low concentration.
This will push water out by osmosis back into the xylem creating a low pressure region.
The difference in pressure between the source and sink drives the movement of substances in the phloem.
what do multicellular organisms require?
Multicellular organisms require effective and efficient transport to be able to move substances around the organism. This ensures all the cells are supplied with the required nutrients and gases as well as the removal of wastes.
what are the similarities and differences the system has in both plants and animals?
In both plants and animals, the system has similarities:
▪ a system of vessels
▪ a suitable transport medium
▪ a driving mechanism
The differences are found in the type of structures and components that are present, the substances that are transported and the mechanisms that drive the movement
what transport occurs in plants?
Plants
▪ vessels
− xylem and phloem
▪ transport medium − water
▪ driving mechanism
− xylem: transpiration-cohesion-t ension theory
− phloem: translocation – source-sink theory
what transport occurs in animals?
▪ vessels
− arteries, veins and
capillaries
▪ transport medium
− blood
▪ driving mechanism
− the heart
what are the changes in composition?
Changes in Composition
The composition of the fluids in plants and animals change as they move around and pass through various organs and tissues. The basic structure of water and blood will remain the same, however the concentration of dissolved substances and gases change.
