Module 3.1.3 - Transport in plants Flashcards
What is the phloem and xylem known as?
Vascular tissues which are responsible for the transport of reactants and products of the chemical reactions around the plant
What is the xylem responsible for?
Transporting water and mineral ions from roots to leaves
What does lignin do in the xylem?
- waterproofs and reinforces the xylem so it doesn’t collapse under the transportation pull
- leads to death of xylem cells (loss of cytoplasm and end walls organelles)
What is lignification?
Lignin in cell walls
What happens when lignification isn’t complete?
Leaves gaps in cell walls called bordered pits which are in 2 adjacent xylem vessels that are aligned to allow water to leave 1 and pass into the next and out of the xylem and into living parts of the plant
What is capillary action in xylem vessels?
Forces holding water molecules also attract the molecules to the side of the xylem vessels. These forces of attraction can pull the water up the sides of the vessel
What is parenchyma?
Packing tissue which fills spaces between xylem and phloem tissues,
- living tissue, acts to separate/ support the vessels
What does the phloem do?
Transports amino acids, dissolves sucrose in water to form cell sap is transported by the phloem
What are the amino acids and cell sap made from in the phloem?
From the plant using substances absorbed from the environment which then becomes part of the plant
What are sieve tube elements in the phloem?
Cells that are lined up end on end to form sieve tubes, don’t have a nucleus, very little cytoplasm which leaves lots of space for cell sap to move along the phloem vessel by mass flow
What does perforations in cross-walls (sieve plates) allow?
Cell sap to move from 1 sieve tube element to another
What does the phloem consist of?
Sieve tubes, formed of sieve tube elements lined end on end and companion cells
What do companion cells do in the phloem?
Carry out active processes which are needed to load the assimilates into the sieve tubes
Where are companion cells found?
Between sieve tubes, small cells, large nucleus, dense cytoplasm containing an abundance of mitochondria
What is the plasmodesmata?
Thin strands of cytoplasm that links contents of adjacent cells
How are companion cells and sieve tube elements linked?
Plasmodesmata which allows the flow of assimilates between the cells
What do root hair cells have?
Large surface area and a lack of cytoplasm which contains a large number of mitochondria
How do mineral ions enter the root hair cells?
Active transport - require energy from the hydrolysis of ATP to move the ions against the concentration gradient
What happens to the water potential inside the root hair cell because of ions going against the conc gradient?
Water potential decreases so water will move from higher water potential in the soil to the lower water potential in the root hair cell by osmosis
What is the epidermis?
Outermost cell layer of a plant and root hair cells are located in this outer layer in the roots
What is the root cortex?
Series of plant cells that extend inwards
What is the symplast pathway?
Water and mineral ions pass through the plasmodesmata from 1 cell to the next, down the water potential gradient
What is the vacuolar pathway?
Water and mineral ions go to cytoplasm and then pass through vacuoles too
What is the apoplast pathway?
Cell walls are fully permeable so water can move freely between cells without needing to pass through the plasma membrane. Moves by mass flow which allows dissolved mineral ions to be carried through the root cortex
What is the endodermis?
A cylinder of cells that forms the final boundary between the cortex and the inner region of a plant
Where is suberin found?
The walls of the root endodermis cells
What is suberin?
Waterproof and impermeable which creates a water tight seal known as the casparian strip
What does the casparian strip do?
Blocks the apoplast pathway between the cortex and medulla so water and mineral ions have to pass into the cytoplasm
What happens to water and mineral ions due to the apoplast pathway being blocked?
Have to pass into the cell cytoplasm
What do transporter proteins do?
Actively pump the mineral ions into the medulla, the water potential of the medulla decreases