Chapter 9- Transport in plants Flashcards
What is the need for transport for plants?
Metabolic demand
Size
Small SA:V ratio
What is the need for transport in plants?
Metabolic demand
Size
Small SA:V ratio
What are Dicotyledonous plants (Dicots)?
Make seeds that contain two organs that act as food stores(cotyledons)
What are the 2 main types of dicots and their features?
Herbaceous- soft tissues and a relatively short lifecycle
Arborescent- woody and long life
What is parenchyma?
Packing and supporting tissue which transports food and tannin deposits
What are tannins?
A bitter chemical in parenchyma that deters predators
What is plasmodesmata?
Microscopic channels in the cell walls which links to the cytoplasm for substance transport
What are the 2 ways for water to move from the roots to the xylem of a plant?
Symplast pathway
Apoplast pathway
What is the symplast?
Continuous cyptoplasm of living cells that is connected through plasmodestamta
What is the symplast pathway?
1- Water moves through the symplast by osmosis
2- Water potential is high as joining cells do not contain water
3- After water leaves, water potential falls maintaining a steep concentration gradient
What is the apoplast?
Space between cell walls and intercellular spaces
What is the apoplast pathway?
1- Water fills between cavities
2- As H2O moves through cell walls, more water is pulled through apoplast due to cohesive forces between molecules.
3- The pull of water creates tension and a continuous flow of water
What is suberin?
Waxy layer that lines the endodermis
Contains a waterproof layer that is called the casparian
What is the transpiration pull?
1- Water molecules evaporate out of mesophyll layer surface through stomata into the air
2- Creating a lower H2O potential in that layer- H2O from cell below moves up
3- This process moves up into the xylem
4- Water molecules form hydrogen bonds with carbohydrates in the walls, this is called adhesion
5- Water molecules form the hydrogen bonds with each other and tend to stick together, this is called cohesion
6- Combined effects of adhesion and cohesion result in water capillary action which causes the H2O to rise up a narrow vessel against gravity
What is the cohesion tension theory?
The model of water moving in a continuous stream up the xylem
What is active loading?
Loading sucrose into sieve tube elements
High conc. of sugar in companion cells cause sucrose to diffuse into sieve tube elements
What is translocation?
1- Hydrogen ions are transported from inside the companion cells across the membrane against the concentration gradient to the leaf tissue, this uses energy so is active
2- Hydrogen + ions and sucrose are diffused back into the companion cell down a concentration gradient. They are transported by a cotransporter protein
3- There is now a higher concentration of sucrose in the companion cells than the phloem which the sucrose diffuses into
4- As a result of the movement of sucrose, water moves into the cell via osmosis which increases turgor pressure due to rigid cell walls
5- Water moves into the tubes pf the sieve tube elements which reduces pressure in the companion cells
What are xerophytes and their adaptions?
Plants in desert regions or icy and cold places
Adaptions- thick waxy cuticles, sunken stomata, reduced stomata, reduced leave/curled leaves, hairy leaves, leaf loss and deep reaching tap roots
What are hydrophytes and their adaptions?
Found in water
Have floating leaves for photosynthesis
Adaptions- very thin waxy cuticle, many open stomata with inactive guard cells, reduced structure, large flat leaves, large SA:V ratio
What is aerenchyma?
Supporting tissue found in stems and roots
Makes leaves and stems buoyant
Forms low resistance pathway for movement of substances
What are mesophytes?
Land plants that have a waxy cuticle and green leaves
Well developed root systems that provide anchorage and allows for efficient absorption of H2O and minerals
