3.3 Flashcards
What kind of structures do all land plants have?
structures below ground that absorb water and minerals, structures above ground that photosynthesize, and structures that link the two together
What system do vascular plants have for absorption?
Organ and organ systems
What systems do vascular plants have for transport and photosynthesis?
Roots, stems, and leaves
How are roots, stems, and leaves organized in two systems?
The shoot system: stems and leaves above ground
The root system (below ground)
What do shoot systems (stems and leaves) do?
Photosynthesize sugars, conserve water, provide aerial support at different levels
What do root systems do?
Anchor the plant in the soil, absorb water and minerals, store material produced in the shoot for later use
Plants use __, __, and __ ___ to absorb materials and move them over __ distances.
Diffusion, osmosis, active transport, short
What is only moved by diffusion over short distances?
O2 and CO2
What is only used to move water, sugar, and nutrients over long distances?
bulk transport
What do diffusion, osmosis, and bulk transport move?
water, minerals, and sugar into and out of cells
How do cells maintain equilibrium?
Molecules move from higher to lower concentration - down a concentration gradient
What is the definition of osmosis?
diffusion of water across a semi-permeable membrane (a membrane that prevents movement of non-water molecules)
What does the movement of water depend on?
Concentrations of the non-water molecule called solutes
Does water move into areas with more or fewer solutes?
More solutes, there is less water there and they are maintaining equilibrium
What does it mean to move against the concentration gradient?
Areas of lower concentration to higher
What is active transport?
Materials moving against the concentration gradient, concentrating materials in cells
Does active transport require energy?
yes
what is osmotic pressure or solute potential?
The osmotic pull on water across a membrane by hypertonic solutions
What is a hypertonic solution?
any external solution that has a high solute concentration and low water concentration
What happens when there is more hypertonic in a solution?
The greater the pull on water it will have
What does it mean when we say pure water has no osmotic pull?
It’s always hypotonic to other solutions
True or false: cells are made of pure water
False, they contain some solutes
What does a cells osmotic pull depend on?
Their solute concentration compared to the solution outside their membrane.
How can osmotic pulling pressure of a plant cell be counteracted?
Turgor pressure
What is turgor pressure?
A pushing pressure of the cells contents against the cell wall
What helps a cell keep upright?
Cell turgor pressure
What happens when a plant has low turgor pressure?
It wilts
Does water always move? How?
Water always moves by osmosis into and out of cells
How do organisms cause water to move and out of them?
organisms can manipulate the solute concentration of their cells
What is active transport?
Energy generated by the cell
What mechanism do organisms use to manipulate their solute concentration?
Active transport
Where does energy come from and how is it produced?
Energy comes from ATP produced by cellular respiration
What do guard cells do?
Regulate gas exchange and limit water loss
How many guard cells surround the central pore?
2
The guard cells can __ or __, changing the size of the __ and ___ or ___ the stoma
The guard cells can shrink or swell, changing the size of the pore and opening or closing the stoma
What mechanism do guard cells use to open stoma?
Active transport
What is pumped into guard cells to open them?
K+ and CL- ions
What does blue light trigger?
Transportation of potassium+ and chlorine- ions into guard cells
What is a hypotonic solution?
A solution that contains a lower amount of solute as compared with the solute concentration in the other solution
What is a hypertonic solution?
A solution that contains a higher amount of solute as compared with the solute concentration in the other solution
What makes the guard cell hypertonic?
Extra ions are not allowed to move out through ion channels
How does water move into the guard cells and why
The guard cells are hypertonic, they have a lower amount of solute, so water moves in by osmosis to maintain homeostasis
What happens when osmosis moves water into the guard cells?
Guard cells swell and stoma opens
What is pumped out of guard cells to close them and how?
Ion channels open to allow K+ and CL- ions to move out of guard cell by diffusion
What triggers a guard cell to close?
The absence of light or abscisic acid (stress hormone)
What happens once the potassium and chlorine move out of the guard cells?
They are no longer hypertonic so they become hypotonic (lower concentration of solute) so water moves out by osmosis
What happens once water moves out of the guard cell?
The guard cells wilt and collapse againts each other, resulting in a closed stoma
What must happen once a plant absorbs water, sugar, or nutrients?
They must be transported over long distances through the vascular tissue
Where does bulk transport take place?
In the xylem and phloem
What are the 4 anatomical functions of xylem
Xylem cells are greatly elongated with pits for water flow
Xylem cell walls contain lignin that increase strength
Mature xylem cells die leaving behind thick cell walls
The cell walls form hollow connected tubes for water
What is mature xylem
thick cell walls without cytoplasm or cell membranes
Water and mineral transport in xylem does not cross any cell membrane. What does that mean?
Water cannot move by osmosis
What are the three things plants must do to maintain water?
Transport water under different environmental conditions
Lift water over 367 feet (highest tree in the world)
Transport water using a minimum of energy (can move gallons of water)
What does long distant water transport in xylem rely on?
Tension, a pulling force
What does long distant water transport in phloem rely on?
pressure, a pushing force
What direction does water in xylem move?
Upward from the roots to the shoots
What direction does water in phloem move?
In different directions from sources to sinks
What do plants use to move xylem water from root to leaves?
Cohesion-tension mechanism
How is water pulled in cohesion-tension mechanism?
Water is pulled up to the tops of trees by evaporation of water at leaf surfaces.
What is the movement energy traits of the cohesion-tension mechanism
Movement of water and minerals is upwards and movement is passive, it does not require energy from the plant.
Explain tension, adhesion, cohesion, and transpiration
The pull (tension) generated by evaporation of water at the leaves is transmitted through the water in xylem all the way down to the water in the xylem of roots. Water molecules stick to each other (cohesion) and stick to the walls of xylem cells (adhesion).Water evaporates out of leaves (transpiration).
What data supports the cohesion-tension theory?
Testing a plant in conditions that alter respiration resulting in pressure changes. Test the plant at low, medium, and high light intensity. If the pressure decreases, then there is less water allowing for more space
What is negative pressure in xylem cells?
If the water in the xylem is under tension compared to the air pressure outside the cell
What is decreasing pressure in xylem cells?
As evaporation increases tension the pressure inside the xylem decreases
What tree experiments provide data for the cohesion tension theory?
Charting how the diameter of a tree changes over hot and cold days. Results showed that xylem is narrow on hotter days, resulting in a lower diameter.
What are the risks of transpiration?
Xylem walls rigid with lignin, cavitation (the water being replaced with an air bubble) results in failed transport in conduits
Why do plants have to move more water than needed?
The water must evaporate to create tension, water evaporation cools the leaves, and the stoma causes some water loss.
What is the photosynthesis-transpiration compromise?
The balance between conserving water and maximizing photosynthesis is a fitness trade-off
What is translocation in phloem?
The movement of sugars in phloem is upwards and downwards
What does phloem transport?
Sugar, carbohydrates, amino acids, nitrogen, ions, hormones, protein signals, and RNA
What is a source?
Tissue where sugar enters the phloem, high concentration
What is a sink?
Tissue where sugar exits the phloem, low concentration
What does phloem consist of?
Sieve elements and companion cells
What are sieve elements?
Tubes connected end-to-end. They lose most of their intracellular structure, including the nucleus and vacuole, but they are alive
and retain their cytoplasm and cell membranes
What are companion cells?
Companion cells next to each sieve element carries out cellular functions such as protein synthesis. They are connected to sieve elements by strands of cytoplasm-plasmodesmata.
How does translocation work in 2 summaries?
Translocation stops is phloem is killed, and translocation requires energy from the plant
What can kill phloem?
Emerald ash borer, and heat or chemical
What stops energy for translocation?
If the ATP from cellular respiration is inhibited
Explain turgor pressure in sink and source phloem, as well as the difference in-between
Turgor pressor in sink phloem is low because water flows out by osmosis as sugar exists the phloem and utilized by sink cells. Pressure different between source and sink drives the movement of phloem sap, and turgor pressure in source phloem is high because water is drawn in by osmosis as sugar are added to the phloem
What is phloem loading?
Moving sugar into the phloem
How does sugar move?
By diffusion or active transport from source cells into phloem
What happens once sugar enters phloem?
The sugar levels make them hypertonic and increases the cells’ osmotic pull of water
What is phloem unloading?
Moving sugars out of the phloem
What happens when sugar is unloaded by sink cells?
The phloem become less hypertonic and have less osmotic pull, water gets pulled back into xylem cells by tension
What is moving sugar from source phloem to sink phloem called?
translocation
If water moves into a cell, what happens to the sap pressure?
The sap pressure pushes the sap through the phloem. Water can then be pulled out by sinks due to tension, this is where sap pressure is lowest
Is sap pressure passive or does it require energy?
Sap pressure is passives, it carries sugars in phloem over long distances
What moves sugar into and out of the phloem over a short distance?
Active transport or diffusion
What is a positive pressure in phloem
A pushing force
What is a negative pressure in xylem
A pulling force
Are osmosis/turgor and positive/negative pressure that same?
Nope
