Plant tissues, organs and systems Flashcards
What are the layers of a plant leaf?
- waxy cuticle
- upper epidermis
- palisade mesophyll
- spongy mesophyll
- lower epidermis
- guard cells and stomata
What does the waxy cuticle do?
Protective layer on top of the leaf, prevents water form evaporating
What does the upper epidermis do?
Thin and transparent to allow light to enter palisade mesophyll layer underneath it
What does the palisade mesophyll do?
Column shaped cells tightly packed with chloroplasts to absorb more light, maximizing photosynthesis
What does the spongy mesophyll do?
Contains air spaces that increases the surface area to volume ration for the diffusion of gases
What does the lower epidermis do?
Contains guard cells and stomata
What do guard cells do?
Absorbs and loses water to open and close the stomata to allow carbon dioxide to diffuse in, oxygen to diffuse out
What does the stomata?
Where gas exchange takes place ; opens during the day, closes during the night. Evaporation of water also takes place from here.
Reduces water loss
What are the adaptations of the leaf? (5)
large surface area thin chlorophyll stomata waxy cuticle
How do plants having a large surface area help it survive?
Increases surface area for the diffusion of carbon dioxide and absorption of light for photosynthesis
How do plants being thin help it survive?
Allows carbon dioxide to diffuse to palisade mesophyll cells quickly
How do plants having chlorophyll help it survive?
Absorbs light energy so that photosynthesis can take place
How do plants having stomata help it survive?
Allows carbon dioxide to diffuse into the leaf and oxygen to diffuse out
How do plants having waxy cuticle help it survive?
Protects leaf without blocking sunlight
How are root hair cells specialised and what do they do? (4)
Absorb water/minerals for plants
- Large permanent vacuole - speeds up movement of water by osmosis from soil across root hair cell - maintain potential gradient
- Have many mitochondria that transfer the energy needed for active transport of mineral ions into root hair cells
- Thin walls = short diffusion distance
How are xylem cells specialised and what do they do? (4)
Transports water and mineral ions from the roots to the highest leaves/shoots.
Supports plant
- Alive when the first form but lignin build up in spirals in the cell walls. Cells die and form long hollow tubes - allow water/mineral ions to move through them easily
- Rings of lignin make them strong and help them withstand the pressure of water moving up.
How are phloem cells specialised and what do they do? (4)
Carries the food made by photosynthesis around the body of the plant
- Made of phloem cells that form hollow tubes
- Lose a lot of their internal structure but they are supported by companion cells
- Companion cells have mitochondria that transfer energy
What is meristem tissue?
Found at the growing tips of shoots and roots, can DIFFERENTIATE into different types of plant cell, allows plant to GROW
Factors affecting transpiration: (4)
Light intensity
Temperature
Air flow
Humidity
How does light intensity affect transpiration?
Brighter the light, the higher transpiration rate
The stomata close as it gets dark, photosynthesis can’t happen in the dark, so they don’t need to let CO2 in, very little water can escape.
High light, stomata stays open to allow co2 in.
What is transpiration?
The evaporation of water at the surfaces of the spongy mesophyll cells in leaves, followed by loss of water vapour through the stomata
How does temperature affect transpiration?
Warmer, faster transpiration
When it is warm the water particles have more energy to evaporate and diffuse out of the stomata
How does air flow affect transpiration?
better the air flow, faster the transpiration
Water vapour is swept away maintaining a low concentration of water in the air outside the leaf. Diffusion happens quickly
How does humidity affect transpiration?
Drier the air, faster transpiration
Lots of water in the air, not much of a difference between inside and outside the leaf so diffusion happens slower
What is translocation?
Movement of food/sugars from the leaves to the rest of the plant, goes in both directions
When do guard cells and stomata become turgid?
In the light, the guard cells absorb water by osmosis , become turgid and the stoma opens. In the dark, the guard cells lose water, become flaccid and the stoma closes.
