Chapter 9 (Transport in Plants) Flashcards
(16 cards)
What is the symplast pathway?
Water moves through the cytoplasm by osmosis
What is the apoplast pathway?
Movement of water through cell walls and intercellular spaces by cohesion
What is evidence for the role of active transport in root pressure?
• Some poisons affect production of ATP. If cyanide is applied, the root pressure disappears
• Root pressure is affected by temperature, suggesting enzymes are used
• If levels of oxygen or respiratory substrates fall, root pressure falls
• Xylem sap is forced out of the pores at the end of leaves
What is parenchyma?
Packing and support tissue
What are the functions of the xylem?
Transport of water and mineral ions
Support
Where does water leave the xylem cells from?
Non lignified pits
What is xylem parenchyma?
Stores food around the xylem and contains tannins
What are the transporting vessels of the phloem?
Sieve tube elements
What do the ends of phloem cells become?
Sieve plates
What are companion cells?
Linked to sieve tube elements by plasmodesmata
Very active, possibly acting as a life support system for the sieve tubes
What is water needed for in plants?
• Plant support
• Root cell expansion through the ground (caused by turgor)
• Evaporation helps keep plants cool
• Minerals and products of photosynthesis are transported in a solution
• Needed for photosynthesis
How are root hair cells adapted as exchange surfaces?
• Small, so fit between soil particles
• Large SA:V ratio
• Thin pathway for substance exchange
• High concentration of solutes in cytoplasm
Why is the Casparian strip useful?
It forces water from the apoplast into the symplast pathway through partially permeable membranes, which filters out any toxic substances
What are endodermal cells in water transport in plants?
Cells just before the xylem, containing the Casparian strip
How do endodermal cells ensure water enters the xylem?
Cytoplasm in endodermal cells is relatively dilute compared to the xylem, so water moves by osmosis
Endodermal cells move mineral ions into the xylem by active transport
What is root pressure?
When minerals are pumped into the xylem so water moves by osmosis
