Water Relations Flashcards
Briefly describe bulk flow, diffusion and osmosis
All 3 processes involve water movement
Bulk flow: water molecules move together due to differences in energy potential. (River/ocean currents)
Diffusion: dispersion of molecules over time to equalize concentration.
Osmosis: net movement of water through a selectively permeable membrane. Flows from high water concentration to lower water concentration.
What are is a major difference when it comes to how vessels and trancheids transport water?
Vessels
form a continuous tube from tip to top of tree for water transportation. Pits are fewer and less pronounced.
Tracheids
Do not form a continuous tube but transfer water through interconnected pits. Heavily pitted for better water transfer
How do roots absorb water?
Water is absorbed through root hairs by osmosis due to a higher concentration of solutes inside the root which lowers its osmotic potential, allowing for inflow of water.
What defines Osmotic or water potential?
What direction does water flow when high and low osmotic potentials interact?
Osmotic potential is defined by the concentration of solutes in water. Water with a high osmotic potential has little or no solutes in it.
Water flows from high to low osmotic potentials when interacting across a selectively permeable membrane
What is turgor pressure?
How do plant cells create turgor pressure?
Pressure in a cell that results from osmosis.
Cells absorb the water due to their high concentrations of sugars, amino acids and other solutes that create a low osmotic potential.
What is Transpiration?
How much of the water taken up by a plant is transpired away?
Transpiration is water loss through the leaf surfaces of a plant. It is largely a result of photosynthesis and the loss is in the form of water vapours that escape when the stomata are open to absorb CO2
99.7%
How fast is water absorbed by roots?
Rate depends on length of path
How does water get through root and into vascular tissue?
Once water is absorbed by root hairs, it moves between intercellular spaces and the cytoplasm of the cortex. Eventually root pressure builds up and helps water permeate the endodermis where it moves through the pericycle and into the xylem.
Explain the difference between the apoplast and the symplast.
The symplast refers to the cytoplasm of cells
The apoplast refers to the intercellular spaces between cells
What molecular quality of water allows it to be pulled up a tree in a continuos chain?
As outlined by the cohesion tension theory, the polarity of water makes it cohesive so that it sticks together as it is pulled up through the xylem of a tree.
Describe transpirationall pull
Due to the high saturation of water vapour inside the leaf, water escapes from the stomatal pores when they open to take in CO2 due to lower saturation of water in the outside environment. It is the constant loss of water through the leaves that create the suction we know as transpirationall pull that is responsible for all upward water movement in plants.
How much energy is used by a tree to transport water in one day?
None!
Transpiration is a passive force of nature that played a major role in the evolution of plants.
Clearly Mother Nature is looking out for them…
What is a ball park estimate of how much water a 16 meter tree would transpire in an hour during the day?
Around 200 l per hour during the day
How does phloem transport solids?
Solids in the phloem are dissolved in water that gets re-circulated from the xylem and from the leaf itself.
