Organisation - Plant tissues, organs and systems Flashcards
what is the epidermal tissue
tissue which covers the whole plant and protect the surface of the leaf
examples of plant organs
stems , root , leaves, reproductive structures
what is the palisade mesophyll tissue
part of the leaf where most photosynthesis happens
what is the spongy mesophyll tissue
part of the leaf that has big air spaces to allow gases to pass through
- The air spaces allow carbon dioxide to diffuse from the stomata ,through the spongy mesophyll to the palisade cell
what are the xylem and phloem for
transporting things like water, food and mineral ions around the plant
what is the meristem tissue
found at the growing tips of shoots and roots and is able to differentiate into lots of different types of plant call, allowing the plant to grown
how is the epidermal tissues specialised to do its job
covered with a waxy cuticle which helps to reduce water loss toprevent the leaf from drying out
how is the upper epidermis specialised to do its job
transparent so that light can pass through it to the palisade layer
how is the palisade layer specialised to do its job
has lots of chloroplasts so they can capture the most light
how does translocation work
- phloem is made up of columns of elongated living cells with small pores in the end walls to allow cell sap to flow through
- transport food substances made in the leaves to the rest of the plant for immediate use or storage
- transport goes in both directions, this is translocation
How does the transpiration stream work
- xylem made of dead cells joined end to end with no end walls
- they carry water and mineral ions from the roots to the stems and leaves
- the transpiration stream is the movement of water from the roots, through the xylem and out of the leaves
Explain the transpiration stream
Transpiration starts with the evaporation of water from cells inside the leaf.
The water vapour, then diffuses through the air spaces in the spongy mesophyll and out of the leaf through the stomata
Then water passes from the xylem into the leaf to replace the water that has been lost
Finally, water is drawn into the root hair cell and up the xylem vessels into the leaf
how is the lower epidermis specialised to do its job
full of little holes called stomata, which let CO2 diffuse directly into the leaf
how does light intensity affect transpiration rate
- brighter light, greater rate of transpiration
- this is because as it gets darker, the stomata starts to close and photosynthesis can’t happen in the dark
- when the stomata is closed, very little water can escape
- The rate of photosynthesis increases so the stomata open to allow the carbon dioxide in and allow water vapour to leave
how does temperature affect transpiration rate
warmer, faster rate of transpiration
- this is because when its warm, evaporation is faster
how does air flow affect the rate of transpiration
the better the air flow ( strong wind ) the faster the transpiration rate
- this is because when there is good air flow, water vapour is swept away, maintaining a low concentration of water in the air outside the leaf, diffusion then happens quicker
how does humidity affect the transpiration rate
the drier the air around a leaf , the faster transpiration happens
- this is because if the air is humid, there’s a lot of water in it already, so theres not much of a difference between the inside and outside of the leaf, and diffusion happens fastest when one area is more concentrated than the other
how are guard cells adapted for their job
- job is to open and close the stomata and for gas exchange and controlling water loss on a leaf
- thin outer walls and thickened inner walls make the opening and closing work
- When there is a high light intensity, they swell up, causing them to open so co2 can diffuse into the leaf and be used in photosynthesis
- In hot conditions, the plant closes its stomata to reduce water loss by transpiration, meaning that the plants can no longer photosynthesise
where do you usually find stomata
in the lower epidermis
What is the function of the stomata
allow carbon dioxide to enter the leaf and oxygen to leave
- They also help control the amount of water vapour that can pass out of the leaf
difference between xylem and phloem vessels
phloem is bidirectional whilst xylem travels only in one direction
phloem transports food used in photosynthesis and xylem transports water and minerals
describe the transport of water through a plant from the roots to the atmosphere
- xylem carries water from roots to stem and leaves
- the water evaporates from the leaves through the stomata
what is transpiration
the loss of water from the surface of leaves
what is transpiration caused by
the evaporation and diffusion of water from a plants surface
describe the structure of a xylem
- made up of dead cells joined end to end with no end walls between them for continuous flow of water
- they are strengthened with a material called lignin
- they carry water and mineral ions from the roots to the stems and leaves (one direction)
describe the structure of a phloem cell
- made up of columns of long living cells with small pores in the end walls to allow cell sap to flow through
- They transport food substances (mainly dissolved sugars) made in the leaves to the rest of the plant for immediate use or for storage
- transport is bidirectional
why do stomata close as it begins to get darker
because photosynthesis cannot happen in the dark, so they dont need to be open to let CO2 in, very little water can escape when stomata is closed
why would you find more stomata on the undersides of leaves rather than the top
because the lower surface is shaded and cooler, meaning less water is lost through the stomata than if they were on the top
what happens when there is a lot of water in a plant
when the plants have a lot of water, the guard cells fill with it and go plump and turgid, making the stomata open so gases can be exchanged for photosynthesis
what happens when there is a lack of water in a plant
- when the plants short of water, the cells lose water and become flaccid, making the stomata close, this helps stop too much water vapour escaping
What is the function of the xylem?
It transports water from the roots to the stems and the leaves
-Xylem also transports dissolved mineral ions. these include magnesium, which is used to make chlorophyll
What is the function of the phloem?
- phloem tissue transports dissolved sugars produced by photosynthesis from the leaves to the rest of the plant
- The sugars that are produced can be stored as starch or can be used for respiration
What is translocation?
The movement of sugars and other molecules through the phloem tissue
How does water enter the roots of plants?
through the root hair cells
Why is transpiration important?
Because it brings water to the leaves and water is required for photosynthesis
- The transpiration stream transport dissolved mineral ions, such as magnesium, which play important roles in the plant
- The evaporation of water from the leaves cools the leaves down, especially in warm weather
why are stomata on the underside of the leaf
to reduce water loss by transpiration.
