Chapter 36 Resource Acquisition and Transport Flashcards
What is short-distance transport?
Movement of water and solutes within cells and tissues.
What is long-distance transport?
Movement of water and solutes through xylem and phloem across the plant body.
What does the stems serve as?
Serves as conduits for water and nutrients as supporting structures for leaves
What is phyllotaxy?
Arrangement of leaves on a stem, is a species-specified trait important for light capture
What is canopy?
Leafy portion of all the plants in a community; its depth affects productivity of each plant
What is self-pruning canopy?
Shedding of the lower shaded leaves occurs when they respire more then photosynthesize
What affects light absorption? (2 things)
- leaf area index
- leaf orientation
What is leaf area index?
the ratio of total upper leaf surface of a plant divided by the surface area of land on which it grows
What is low light leaf orientation?
Horizontal leaves captures more sunlight
What is sunny conditions leaf orientation?
Vertical leaves are less damaged by sun and allows light to reach lower leaves
Roots competitveness
Roots are less competitive with other roots from the same plant than with roots from different plants
What are the 2 major pathways through plants?
- Apoplast
- Symplast
What is apoplast?
Consists of everything external to the plasma membrane
What is a symplast?
Consists of the cytosol of all the living cells in a plant, as well as the plasmodesmata
What are the 3 transport routes for water and solutes
- apoplastic route: thru cell walls and extracellular spaces
- symplastic route: through the cytosol
- transmembrane route: across cell walls
What is osmosis?
Diffusion of water into or out of a cell that’s affected by solute concentration and pressure
What happens if an area has a higher solute and less water?
Water moves towards the higher solute to balance everything out
What is an example of active transport for the plasma membrane?
Plant cells using the energy of H+ gradients to cotransport other solutes
What is water potential?
Measurement that combines the effect of solute concentration and pressure
What does water potential refer to?
Refers to water’s capacity to perform work
Higher water potential vs lower water potential
low solute vs high solute
What is the formula for water potentia?
solute potential + pressure potential
What is the measurement of water potential
Megapascal (MPa)
What is solute potential?
Solution is directly proportional to its molarity
What is pressure potential?
Physical pressure on a solution
What is turgor pressure?
Pressure extending by the plasma membrane against the cell wall, and the cell wall against the protoplast
What is a protoplast?
Living part of the cell, which also includes the plasma membrane
What is plasmolysis?
When a cell loses water and the plasma membrane pulls away from the cell wall.
What is a flaccid (limp) cell?
A cell when placed in an environment with a higher solute concentration, cell will lose water and undergo plasmolysis
What does root hairs do?
increase the surface area for absorption.
What is the casparian strip?
waxy layer of the endodermal wall blocks apoplastic transfer of minerals from the cortex to the vascular cylinder
What is the endodermis?
Innermost layer of the cells in the root cortex
What does the endodermis do?
surrounds vascular cylinder; acts as the last checkpoint for selective passage of minerals from cortex into vascular tissue
bulk flow vs. diffusion (5 things)
- doesn’t require energy from plant
- driven by differences in pressure potential only
- moves entire solution
- much faster
- occurs in hollow dead cells only
What is xylem sap?
water and dissolved minerals that are transported from roots to leaves via transpiration
What is transpiration?
Evaporation of water from a plant’s surface
Is sap pushed up from the roots or pulled up by the leaves?
Pulled up by the leaves
What is an example of long-distance transport?
bulk flow: movement of a fluid driven by pressure
Turgid cell
Cell gains water if a flaccid cell is placed in a solution with a lower solute concentration;
Turgor loss causes wilting
What are aquaporins?
Transport proteins in the cell membrane that facilitate the passage of water
What is the cohesion-tension mechanism?
explains how transpiration creates a negative pressure (tension) that pulls water upward through the plant.
cohesion
Hydrogen bonding between water molecules.
adhesion
Attraction between water molecules and the walls of xylem vessels.
Stomata
Small pores on the leaf surface that control gas exchange and transpiration.
Turgid guard cells vs flaccid guard cells in terms of stomata
stomata open (turgid) vs stomata closed (flaccid)
What triggers stomatal opening at dawn?
- light
- CO2 depletion
- internal “clocks” in guard cells -> circadian rhythms (24 hr cycles)
Xerophytes
Plants adapted to arid environments with reduced transpiration rates.
What is the pressure flow hypothesis (pushing xylem sap)? 3 things
water flows in from the root cortex, generating root pressure, a push of xylem sap
What is translocation?
Process of moving producers of photosynthesis through the phloem
What is phloem sap?
An aqueous solution that’s high in sucrose
What is a sugar source?
Organ that’s a net producer of sugar such as leaves
What is a sugar sink?
An organ that’s a net consumer of storer of sugar such as a tuber or bulb
What can storage organ acts as?
Both a sugar sink in the summer and sugar source in the winter
What is pressure flow?
Phloem sap that moves through a sieve tube element by bulk flow driven by positive pressure
How is phloem a “superhighway”?
By it allowing for rapid electrical communication b/w widely separated organs
What influence plasmodesmata to open or close?
- turgor pressure
- cytoplasmic calcium levels
- cytoplasmic pH
