Plant Organisation
- Created by: Abc312
- Created on: 13-05-18 19:05
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- Plant Organisation
- Plant tissues include:
- Epidermal tissues
- Covers the whole plant
- Have a waxy cuticle to help reduce water loss
- The upper epidermal is transparent so water can pass through the palisade layer
- The lower epidermis contains stomata
- Stomata let CO2 diffuse directly to the leaf
- The opening and closing of stomata is controlled by guard cells
- Stomata let CO2 diffuse directly to the leaf
- Palisade mesophyll
- Covers the part of the leaf where most photosynthesis happens
- Lots of chloroplasts
- Near to the top of the leaf to get the most light
- Spongymesophyll
- Contains big air spaces to allow gases to diffuse in and out.
- Xylem and Phloem
- Transport things like water, minerals and food.
- Also help supportive structure
- Meristem tissue
- Found at the growing tips of roots and shoots
- Plant Stem Cells
- Epidermal tissues
- The root hairs cells have a large surface area for better diffusion
- Xylem Tubes
- Made of dead cells joined end to end with no walls between them
- Strengthened with lignin
- Carry water and minerals from the roots to the stem and leaves
- The movement of water through the plant is called the transpiration stream
- Phloem Tubes
- Made of living cells with small pores in the end walls
- Transport food substances made in the leaves to the rest of the plant.
- Goes in both directions
- Called translocation
- Transpiration
- Caused by the evaporation and diffusion of water from a plant's surface
- This causes a shortage of water in the leaf so more is drawn up.
- It can be affected by:
- Light intensity
- Brighter the light means faster the transpiration
- Stomata close as it gets darker.
- Photosynthesis cannot happening the dark so they don't need to be open to let CO2 in
- This also means little water can escape.
- Photosynthesis cannot happening the dark so they don't need to be open to let CO2 in
- Stomata close as it gets darker.
- Brighter the light means faster the transpiration
- Temperature
- The warmer it is the faster transpiration
- When it is warm particles have more energy to evaporate and diffuse out the stomata.
- The warmer it is the faster transpiration
- Air Movement
- The better air flow the faster transpiration
- If there is little air flow water vapour surrounds the leaf meaning there is a high concentration so diffusion doesn't happen as quickly
- The better air flow the faster transpiration
- Humidity
- The drier the air the faster the transpiration rate
- If the air is humid then there is a lot of water in it so diffusion is slow.
- The drier the air the faster the transpiration rate
- Light intensity
- Guard Cells
- If the plant has a lot of water the cells fill with it and go turgid
- This makes the stomata open so it can be exchanged for photosynthesis
- If there is not enough water the cells go flaccid and this stops too much water vapour escaping.
- Thin outer walls and thick outer walls to make them work
- Light sensitive and close at night to save water without losing out on photosynthesis
- There are more stomata under a leaf because it is cooler so less water is lost through them
- If the plant has a lot of water the cells fill with it and go turgid
- Plant tissues include:
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