Plant Transport Flashcards
(45 cards)
Why do plants need transport systems?
Metabolic demands, size and SA:V
What are dicotyledonous plants?
(Dicots) are plants that make seeds. There are herbaceous dicots and woody dicots
What are herbaceous dicots?
Dicots with soft tissues and short lifespans
What are woody dicots?
Dicots with hard, lignified tissues and a long life cycle
What are the structures in herbaceous dicots?
Vascular system, vascular bundles; xylem and phloem
How are vascular bundles arranged in the stem of a herbaceous dicot?
Vascular bundles are around the edge to give strength and support
How are vascular bundles arranged in the root of a herbaceous dicot?
In the middle of the plant to help the plant withstand tugging strains from wind
How are vascular bundles arranged in the leaf of a herbaceous dicot?
In the midrib of the leaf to help support the structure of the leaf
What is the xylem?
A structure made of non-living tissue in plants
What is the function of the xylem?
Transporting water and mineral ions, support
How does the structure of the xylem support its functions?
Long, hollow columns with cells fusing end-to-end so water and mineral ions can flow continuously, lignified secondary walls for extra support, lignin in either circles or spirals to reinforce xylem vessels
What are xylem parenchyma?
Thick-walled packs around xylem vessels that store food and tannin (bitter chemical that prevents predatation)
What is the phloem?
Living tissue that transports organic solutes around the plant from the leaves
What is the function of the phloem?
Transport organic solutes (sugars) and amino acids for cellular respiration and synthesis of other molecules, can go in either direction
How does the structure of the phloem support its functions?
Sieve tube elements connected end-to-end to form a long hollow structure, sieve plates at the end of each cell with pores for substances to travel through, companion cells to provide the sieve tube element with regular functions, plasmodesmata between the companion cell and sieve tube element for substances to pass through, supporting tissues and fibers
Why is water needed in plants?
Maintain turgor pressure to support stems and leaves, cell expansion with that turgor, loss of water via evaporation, transport of mineral ions and products of photosynthesis via aqueous solutions, material for photosynthesis
What is the function of root hair cells?
Exchange surface where water is taken into the plant
How are root hair cells adapted to function?
Microscopic size can penetrate between soil particles, each microscopic hair has a large SA:V and there are thousands on each tip, each hair has a thin surface layer to decrease diffusion and osmosis time, concentration of solutes in cytoplasm maintain water potential gradient
How does water move across the root hair cell?
Symplast and apoplast
What is the symplast pathway?
The pathway where water travels via the cytoplasm and plasmodesmata of living plant cells. The root hair cell has a higher water potential than the living cell and therefore, by osmosis, water travels down the water potential gradient and the process continues
What is the apoplast pathway?
The pathway where water travels via the cell walls and intercellular spaces. As the water is moved into the xylem, more water is pulled into the apoplast pathway by cohesive forces that creates a continuous flow
What is the Casparian strip?
A band of waxy material at the endodermis that pushes water from the apoplast pathway into the symplast pathway
How is water transported into the xylem?
The water potential of the endodermal cells and cytoplasm is higher than the xylem, therefore the water molecules move into the xylem via osmosis. Once the water is in the vascular bundle the water is pushed back into the apoplast pathway to enter the actual xylem via osmosis which creates root pressure
What is root pressure?
Gives water a push up the xylem, not always a major factor in water movement from roots to leaves- this is an active process
