Chapter 7 - Transport in plants Flashcards
Why is transport important in plants? (3)
- To move substances from where they are absorbed to where they are needed.
- To move substances from where they are made to where they are needed.
- To move substances to a different part of the plant for storage
Why aren’t gases transported in plants?
Because gases can easily diffuse in and out of the plant
What are the two main transporting systems in a plant? And what do they transport?
Xylem transport water and dissolved inorganic ions (mineral salts) and Phloem transport the substances (sugars) made by photosynthesis
In which direction do xylem and phloem transports move towards?
Xylem transports moves up the plant, towards the leaves, and phloem transports move either up or down.
What is the name given to flowering plants?
Angiosperms
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Draw and label the image of a dicot stem
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What are the characteristics of a dicotyledonous plant? (4)
- seeds that contain 2 cotyledons
- network of veins
- leaves that typically have broad blades and petioles
- tap roots with lateral branches
What are the characteristics of herbaceous dicots? (2)
- short life spans
2. non-woody tissue
What is the function of the epidermis
To provide protection
What is the function of the waxy cuticle?
It is waterproof and helps protect organs from drying out and infection
Which structure helps increase the surface area of roots?
Root hair cells
What is the function of parenchyma? (2)
They are used for storage of foods like starch, and when they are turgid they help to support the plant
What part of the cell do parenchyma cells make up
It forms the cortex in roots and cells, and pith in stems
What is the collenchyma?
A modified version of parenchyma with extra cellulose deposited in the corner of the cells, which provide extra strength.
Where can collenchyma be found?
In the midrib of the leaves.
How does the position of palisade mesophyll cells help its function?
It is found in the upper surface of the leaf, so that it can easily be provided the sunlight needed by the chloroplast to undergo photosynthesis
Why are spongy mesophyll cells called that?
They have a lot of air spaces in them, and they look a lot like sponges
Which type cell surrounds the vascular bundle
endodermis
What cells are under the endodermis?
pericycle
Which cell forms the pericycle?
sclerenchyma
What walls do the sclerenchyma possess?
Primary and secondary walls?
What happens when sclerenchyma mature, and how does that adaptation help with their function?
Mature cells become dead cells, and have lignified walls, helping them with structure and support
What are the name of the vessels that make up the xylem?
xylem vessel elements
Where are phloem and xylem found
vascular bundles
What are the sieve tubes made up of?
sieve tube elements
What is transpiration?
Evaporation of water out of the leaf
What are the factors effecting transpiration?
Light intensity
Wind speed and temperature
Humidity
Dry conditions
What happens if the rate of transpiration exceeds the rate of water uptake? And how will the plant react?
The plant will become less turgid and wilts, therefore closing its stomata to stop more water from being evaporated
What adaptation did the stomata of a xerophytic plant take and how does this help the plant survive?
It’s stomata is sunken and they have a small number of which, and it helps the plant by decreasing transpiration by creating a humid microclimate and reduces air movement over the stomata
What are the two types of water pathways
symplastic and apoplastic pathways
Which pathway does water take in the symplastic pathway?
Along with plasmodesmata
Which pathway does water take in the apoplastic pathway
Through the cell wall
What are the adaptation of a xerophytic plant? (5)
- Thick cuticle to decrease transpiration via waxy cuticle
- Rolled leaf
- trichomes on leaves to catch moist, and decrease the water potential gradient
- lower epidermis has low number or no stomata
- Reduced surface area to volume ratio, which decreases rate of diffusion
What does the xylem in flowering plants contain?
vessel elements, tracheids, and sclerenchyma fibres and parenchyma cells
https://www.cactus-art.biz/note-book/Dictionary/aaa_Dictionary_pictures/xylem_Vessel.jpg
What is the pith made out of?
Parenchyma cells that are used to store starch
Which cells in the xylem are the most involved in the transport of water
vessel elements and tracheids
What are sclerenchyma fibres?
dead elongated cells with lignified walls that help support the plant
What is the function of pits?
they help water move from one cell to another. And in the xylem, it allows water to move in and out of the cell
What are pits?
spores that are closed by a permeable unthickened cellulose cell wall
What is the main reason for water to move up xylem vessels?
The removal of water in xylem vessels (transpiration), reduces the hydrostatic pressure of water in xylem vessels. And because there’s more pressure in the bottom then there is at the top, the water will move to the area of low pressure
Why is it that plants don’t collapse in itself when there’s a high pressure difference?
Because of the strong lignified cell wall
What is the word that describes liquids moving together like a body of liquid?
Mass flow
How do plants get water from soil?
Cells around the xylem pump solutes like mineral ions in to the xylem, decreasing water potential in the xylem, and encourages water from the soil to go up the xylem.
What pathway does water in the soil take to get to the xylem?
Root hair > epidermis > cortex > endodermis > pericycle > xylem
What is magnesium used for in plants?
Synthesis of chlorophyll
Why is the rate of transpiration always higher in the morning?
Stomata are open to absorb carbon dioxide for photosynthesis
Why are cell wall ingrowths important?
increases surface area so that there can be more co-transporter or other types of carrier proteins
Why is the plasmodesmata important?
It allows signalling between cells, it allows symplastic water movement, and allows movement without using protein channels
Describe apoplastic pathway
Water soaks into the walls of the cortex, and seeps across the root from cell wall to cell wall
What pathway does water take when transpiration rates are especially high?
apoplastic pathway
What is the fatal flaw with apoplastic pathway?
When water goes through cortex, they eventually get blocked by endodermis cells
How does the endodermis block water flow?
The cells in the endodermis have a thick waterproof waxy band of suberin in their cell called the Caspian strip
What is suberin made of?
It is composed of a poly-functional long chained fatty acids (suberin acids) and glycerol
What happens to water flow when the cell grows old?
It is harder for water to take the apoplastic or symplastic route because some cells become fully suberised, and water cannot go through. Water has to instead go through ‘passage cells’.
(it is thought that maybe this is used to control which mineral ions pass, or it helps with root pressure)
Which cells are the water in the soil attracted to and why?
The water osmosis to the cytoplasm and cell sap of the root hair cells because they have a lot of inorganic ions and organic substances dissolved in them, and therefore have low water potential
What is an example of mutualism between plants and fungi?
Fungi live in or on the roots of plants, forming mycorrhizas, which is a mass fungi mycelium, which absorb water and nutrients and transport them to plants. In exchange, fungi receive organic nutrients from the plants.
What are some mineral ions that get transported in plants? (6)
Phosphate, magnesium, nitrate, sulfate, potassium, calcium
What does the phloem consist of?
sieve elements, companion cells, parenchyma and fibres
What are the organelles found in a sieve tube element?
cell wall, cell membrane, cytoplasm, mitochondria, smooth ER
Where can sieve plates be found?
Where the end walls of two sieve elements meet
Can the pores in the sieve tube elements be seen with a light microscope?
Yes
Companion cells have an increase of which organelles?
Ribosomes and mitochondria
What is the liquid inside phloem sieve tubes called?
Phloem sap or just sap
What cautions do plants take when a sieve tube is cut?
The phloem starts flowing out of the cut. It may block it this way, but either way, it is properly sealed with a carbohydrate called ‘callose’
What type of plants do not clot cuts made to the phloem tube?
Castor oil plants
How can aphids drink from phloem saps without it clogging?
They use their tubular mouthparts called stylets, which they insert to the phloem. And because the stylet has such a small diameter of the stylet doesn’t allow sap to flow rapidly enough to trigger the plants clogging mechanism
Is there nitrate ions in the phloem?
No
How does translocation move in the phloem (one keyword)
mass flow
How does phloem create the pressure gradient needed for mass flow?
By active loading of sucrose into the sieve elements at the place from which sucrose is to be transported. This decreases the water potential gradient, so water enters the sieve element, which increases pressure
What is an area where sucrose is loaded into the phloem called, and the place where sucrose is taken out of the phloem called?
source and sink, respectively
Why is it important that phloem go up and down the plant?
Because a sink can be anywhere in the plant
Does sucrose move up and down in the same tube?
No, seperate ones
Which type of sugars are converted into sucrose?
triose sugars
How does sucrose go from mesophyll and across the leaf to get to the phoem tissues?
It’s in solution, and therefore takes apoplastic of symplastic pathways
What are the details known about sucrose unloading?
It is probable that they move with symplastic or apoplastic pathway, or they might using similar methods to loading them. But once they are in the tissues, enzymes called invertase convert sucrose to glucose and fructose
Describe the process of loading sucrose into phloem tubes
hydrogen ions are pumped out of companion cells into its cell wall, using ATP as energy source. This creates a large excess of hydrogen ions in the apoplastic pathway outside the companion cell. The hydrogen ions can move back into the cell down their concentration gradient through a protein which acts as a carrier for both hydrogen and sucrose at the same time called a co-transporter. Sucrose is carried into companion cells this way. Which can then move to the sieve tube through the plasmodesmata.
