Plant transport, transpiration and gas exchange Flashcards
What do cells in living organisms need to do with substances?
Cells need to acquire substances and eliminate waste substances.
Why is direct diffusion insufficient for multicellular organisms?
Direct diffusion is too slow due to the large distances substances must travel.
What are the two main transport systems in plants?
Xylem and Phloem.
What does the xylem transport?
Water and mineral ions.
What type of cells make up the xylem vessels?
Dead and hollow cells.
How are xylem cells connected?
Cells join at the ends to form tubes.
What strengthens the cell walls of xylem cells?
Lignin.
What do phloem cells transport?
Sucrose and amino acids.
What are the two types of phloem cells?
- Phloem sieve tubes
- Companion cells
What is the function of phloem sieve tubes?
They leave space for transport and connect end to end at sieve plates.
What is the role of companion cells in the phloem?
They provide materials to the sieve tube cells.
What is the process of transport in the phloem called?
Translocation.
Is transport in the phloem an active or passive process?
Active process.
What energy source is required for translocation in the phloem?
ATP.
What are vascular bundles?
Structures that arrange xylem and phloem in plants.
What is the arrangement of vascular bundles in roots?
One large central bundle that anchors the plant in the ground.
Fill in the blank: The process by which multicellular organisms transport substances is called _______.
transport.
True or False: Xylem cells are living cells.
False.
True or False: Phloem transport is a passive process.
False.
What is the primary function of bundles around the edge of a stem?
To give strength and support, but also flexibility
What are root hair cells and what is their function?
Cells on plant roots that grow into hairs to increase surface area for absorbing water and mineral ions
How is water absorbed by root hair cells?
Via osmosis, down a water potential gradient
Describe the pathway of water absorption in plants.
Soil → Root hair cells → Xylem vessels
How are minerals absorbed by plants?
By active transport, traveling up the xylem dissolved in water within the transpiration stream
Define transpiration in plants.
The loss of water from a plant by evaporation and diffusion from the stoma
Where does transpiration mainly occur in plants?
In the leaves
What happens to water during transpiration?
- Moves across the leaf, cell to cell, by osmosis
- Is lost at the stomata
- Creates a shortage of water, drawing more water from air spaces and spongey mesophyll
What is the result of transpiration for water movement in plants?
A constant water/transpiration stream drawing water through the plant from roots to leaves
What are the factors that affect transpiration?
- Light intensity
- Temperature
How does light intensity affect transpiration?
Increases transpiration by opening stomata for photosynthesis, allowing more water loss
How does temperature influence transpiration?
High temperatures increase the rate of transpiration by increasing evaporation from mesophyll cells
What is the effect of humidity on transpiration?
Reduces the diffusion gradient, slowing down transpiration in humid air, and speeds up in dry air due to a steeper concentration gradient
Humidity affects the rate of transpiration by altering the concentration gradient between the leaf and the surrounding air.
How does wind speed affect transpiration?
Increases the rate of transpiration with faster air movements as it removes water vapor near the stomata
Faster air movements enhance the concentration gradient, leading to more water loss through diffusion.
What does a potometer measure?
The rate of uptake of water by a plant
Potometers can measure water uptake either by weight loss or volume of water taken up.
What are the two types of potometers mentioned?
- Weight potometers
- Volume potometers
Weight potometers measure mass loss, while volume potometers measure the volume of water taken up by the plant.
How can you prevent loss of moisture from the soil when measuring transpiration?
Place a bag over the roots
This ensures that any water loss is solely from the leaves, allowing for accurate measurement of transpiration.
What is one method to investigate the effect of light intensity on transpiration?
Use a lamp to increase light intensity
Increasing light intensity typically increases the rate of transpiration.
How can temperature be manipulated in an experiment to affect transpiration?
By placing the potometer in a hotter or colder room
Hotter environments increase transpiration rates, while colder ones decrease them.
What effect does increasing humidity have on transpiration?
Reduces the rate of transpiration
Trapping water vapor with a bag around the plant decreases the concentration gradient.
What is the role of a fan in an experiment investigating transpiration?
To increase wind speed, thereby increasing the rate of transpiration
Enhanced air movement around the plant leads to a steeper concentration gradient for water vapor.
Fill in the blank: The rate of transpiration ________ in dry air.
increases
A steeper concentration gradient in dry conditions facilitates more water loss.
True or False: Higher light intensity always decreases the rate of transpiration.
False
Higher light intensity typically increases the rate of transpiration.
What two processes rely on the exchange of oxygen and carbon dioxide in plants?
Respiration and photosynthesis
What is the primary method of gas exchange in plants?
Diffusion
In respiration, what gas do plants take in and what do they give out?
Take in oxygen, give out carbon dioxide
In photosynthesis, what gas do plants take in and what do they give out?
Take in carbon dioxide, give out oxygen
What are stomata?
Holes in leaves between guard cells for gaseous exchange
What is the role of stomata in gas exchange?
Allow CO2 in for photosynthesis and excess gases out
What is a consequence of stomata opening?
Water is lost through transpiration
What happens to the guard cells when they take in water?
They become turgid, opening the stomata
What causes stomata to close?
The plant being short of water, causing guard cells to become flaccid
When do stomata tend to open?
When there is lots of water and sunlight
When do stomata tend to close?
When there is little water and sunlight
What happens to gas exchange during the daytime in plants?
Plants both respire and photosynthesize, with a net diffusion of CO2 in and O2 out
What happens to gas exchange during the nighttime in plants?
Plants only respire, with a net movement of O2 in and CO2 out
How does light intensity affect gas exchange in plants?
Higher light intensity increases the rate of photosynthesis
Fill in the blank: The process of gas exchange in plants primarily occurs through _______.
Diffusion
True or False: Stomata only allow for the intake of carbon dioxide.
False
What is the compensation point in photosynthesis and respiration?
The point where the uptake or release of oxygen and carbon dioxide is equal at very low light intensity
This occurs when photosynthesis and respiration rates balance out.
What does hydrogen-carbonate indicator indicate at low carbon dioxide levels?
Purple
This color indicates low levels of carbon dioxide in the solution.
What color does hydrogen-carbonate indicator turn at atmospheric carbon dioxide levels?
Red
This indicates the presence of carbon dioxide at normal atmospheric levels.
What color does hydrogen-carbonate indicator turn at high carbon dioxide levels?
Yellow
This indicates an increase in carbon dioxide concentration.
What happens to the indicator at higher light intensities?
Photosynthesis occurs faster than respiration, causing the indicator to go purple
This signifies that carbon dioxide is being absorbed by the plant.
What occurs at low light intensities in terms of gas exchange?
Respiration happens faster than photosynthesis, causing the indicator to turn yellow
This indicates that carbon dioxide is being produced by the plant.
What is the purpose of including tubes with no plants in the experiment?
To serve as a control and prove that the indicator’s color change is due to gas exchange by the plant, not light
This ensures that any observed changes are due to the plant’s activity.
Fill in the blank: The hydrogen-carbonate indicator goes _____ in low carbon dioxide levels.
Purple
Fill in the blank: At atmospheric carbon dioxide levels, the indicator goes _____
Red
Fill in the blank: At high carbon dioxide levels, the indicator goes _____
Yellow