Water and Plant Relations - 2 Flashcards
What is the biggest challenge for plants
to balance the uptake, transport, and loss of water when exposed to photosynthesis specifically
to prevent desiccation from photosynthesis what must plants do
the must absorb water by the roots and transported throughout the plant body
Define turgor pressure
(hydrostatic pressure) - the force within the cell that pushes the plasma membrane against the cell wall.
What is the function of turgor pressure
necessary for physiological processes = enlargement, stomal openings, transport processes.
contributes to rigidity and stability of primary cell wall (non-lignified tissue)
What is waters high heat capacity important for
controlling and buffering temperature fluctuations in cells
What makes water a good solvent and to be readily transported through a plant body
- hydrogen bonding ability of water
- polar structure
What is waters high latent heat of vaporization important for
is it the amount of energy to convert liquid into vapor (break down H bonds) and is important for moderating temperature of transpiring leaves
What are the three “other” important properties of water that result from H-bonds
- cohesion = mutual attraction between water molecules
- adhesion = attraction of water to solid surfaces (ex. cell walls)
- surface tension = develops in water molecules at air and water interface (forming meniscus). water is attracted more to each other and energy is required to overcome this and this input of energy is called surface tension
Define diffusion
the random thermal motion of molecules, important over short distances
Define osmosis
the net movement of water across a selectively permeable barrier (ex. plant cell membranes)
Define water potential
describes the forces acting on water and affecting its movement
related to chemical potential
What are the 3 major forces influencing the water potential
concentration, pressure, and gravity
Explain concentration potential
solute concentration in cell water, solute dissolved in a solution will decrease the concentration potential
explain pressure potential
pressure in cells, positive means in living cells and negative in dead cells
water is not pumped through plants but moves due to…
in response to gradients in chemical (water) potential
Plants usually have ____ water potential because
negative
because of the high solute content (more solutes than pure water)
Water enters or leaves a cell according to the ____
water potential gradient
(seen by flaccid cell in greater potential and water moves in and vise versa)
What happens to the water potential if a cell is squeezed
its pressure potential increases and the water potential resulting in water flowing out of the cell
cell wall elasticity defines the relation between ___ and ____
turgor pressure and cell volume
What determines how fast cells exchange water with their surroundings
the water permeability of the plasma membrane and tonoplast
How does turgor pressure change as a result of changes in plant cell volume and why
small changes in plant cell volume, greatly changes the turgor pressure because plant cells are rigid
Define aquaporins
integral membrane proteins that form water-selective membrane channels
they alter the rate of water movement, but not the direction or driving force
How is the measure of water status of plants often measured
by water potential
What is the trade-off of plants in regards to the plants water status
trade-off between benefits of being able to carry out physiological processes over a wider range of environmental conditions AND the costs associated with such capability
