Plants Flashcards
Epidermal tissue
Covers the whole plants and are covered with a waxy cuticle to reduce water lost by evaporation. Upper epidermis is transparent so light can pass through to the palisade layer
Palisade mesophyll tissue
Contain lots of chloroplasts so is where most photosynthesis takes place. Near top of leaf so more light can be received
Spongy mesophyll tissue
Contains big air spaces to allow gases to diffuse in and out
Meristem tissue
Able to differentiate into different plant cells to allow the plant to grow
Xylem
Transports water
Dead cells
Carries water + minerals from the roots to the stem and leaves
Movement is called transpiration stream
Phloem
Transports food
Made of living cells
Transport goes in both directions
What is transpiration?
The loss of water from a plant caused by evaporation and diffusion. Stomata is designed for water to leave as there is more water in the plant than outside of the plant
What do guard cells do?
If plant is lacking water, they become flaccid and open to allow water in
If plant has lots of water, the guard cells fill with water making them close and stop water excaping
How is transpiration the side effect of photosynthesis?
The leaves have stomata in them so that gases can be exchanged easily but it causes water to leave the plant through the stomata due to there being more water in the cell than put of it.
How does light intensity effect the rate of transpiration?
The brighter the light, the greater the transpiration rate.
Due to the stomata closing when it’s dark outside as photosynthesis can’t happen in the dark, therefore very little water can escape in the dark
How does temperature affect the rate of transpiration?
The warmer it is, the faster transpiration happens.
Due to the water molecules having more energy to evaporate and diffuse out of the stomata
How does air flow affect the rate of transpiration?
The better the air flow around a leaf (stronger wind) the greater the transpiration rate
If there’s good flow the water vapour is swept away meaning their is a bigger difference between the concentration of water inside and outside of the leaf
How does humidity affect the rate of transpiration?
The drier the air around a leaf, the faster transpiration happens.
If the air is humid it already has lots of water in it so there isn’t much of a difference between the inside and outside of the leaf.
Diffusion happens faster is there is a really high concentration in one place and really low concentration in the other
What is the transpiration stream?
The flow of water through a plant, from the roots to the leaves, via the xylem vessels
What does lignin do in xylem tubes? 🤔🤔
It makes it strong and waterproof so water will not leave except at bordered pits (holes in the lignin) allowing minerals to go to specific places in the plant
