Organisation in plants Flashcards
Give the levels of organisation in plants, starting with organelles.
organelles, cells, tissues, organs, organ systems, organisms
What tissues are the leaf made up of?
Epidermis, palisade mesophyll, spongy mesophyll, xylem and phloem tissues
What is the function of the epidermis in the leaf?
- location and guard cells and stomata.
- upper epidermis cells are thin and transparent so sunlight can pass through to the palisade layer.
What covers the epidermal tissues and what is its function?
The Waxy cuticle:
- helps reduce water loss by evaporation.
-prevents leaf from being damaged form the heat of the suns rays, and damage form insects
The palisade layer has a lot of what organelle and what is its function?
Chloroplast:
- site of photosynthesis.
- Chloroplast contain a special pigment called chlorophyll that is essential for photosynthesis - - They are also at the top of the leaf where they can get most sunlight
What is the function of the spongy mesophyll?
- only contain few chloroplast
- Contains big pockets of air spaces which are essential for gas exchange
What is the function of meristem tissues?
- found at the growing tips of shoots and roots and is able to differentiate (change) into lots of different types of plant cell, allowing plant to grow
Function of the lower epidermis?
- found on the underside of the leaf
- location of stomata and guard cells
Function of the stomata?
- tiny pores found between two guard cells
- widen and narrow to control gas exchange and water vapour loss
Function of the guard cells?
- take in or lose water by osmosis
- swell and open or close stomata
- controlling gas exchange and water vapour loss
How does potassium effect guard cells
- when plants have adequate potassium
- potassium ions (k+) increase the concentration of the solution inside the guard cell.
- causes water to move into the guard cells from more dilute areas by osmosis.
- The additional water leads to the guard cells swelling unevenly because the thicker, inner walls are less flexible than the thinner, outer walls.
How are guards cells adapted to open and close?
- when plant has lots of water the guards cells fill up with it and go plump and turgid
- This makes stomata open so gases can be exchanged for photosynthesis
- when the plant is short of water, the guards cells lose water and become flaccid, making the stomata close. This helps stop too much water vapour form escaping.
- **thin outer walls and thickened inner walls make the opening and closing work
- they are also sensitive to light and close at night to save water without losing out on photosynthesis
What are substances that can diffuse through the stomata? Name 3.
- oxygen: diffuses out of leaf
- carbon dioxide: diffuses into the leaf
- water vapour: diffuses out of the leaf
What is the function of the xylem?
the xylem is a tissue which transports water and minerals from the roots up the plant stem and into the leaves.
How is the xylem adapted for its function?
- A tube of dead cells , strengthened by lignin
- no end walls* to create a continuous tube that allows water to move up through the transpiration stream