Plant tissue Flashcards
Describe the top and bottom of a leaf cell?
The top and bottom of a leaf cell are called the upper and lower epidermis made from epidermal cells and they form the epidermal tissues
The epidermis protects the surface of the leaf
How is the epidermis adapted?
It is transparent which means it allows light to pass through to the photosynthetic cells below
The upper epidermis is covered by a waxy cuticle, which reduces the evaporation of water from the surface of the leaf to prevent it from drying out
The lower epidermis contains stomata which allow carbon dioxide to enter the leaf and oxygen to leave
Stromata also control the amount of water vapor that can pass out of the leaf
What is the palisade mesophyll made of?
Palisade cells
What is the function of palisade cells?
Palisade cells are packed with chloroplasts, which contain chlorophyll which absorbs light energy needed for photosynthesis
Why are the spongy mesophyll full of air?
The air spaces allow carbon dioxide to diffuse from the stomata through the spongy mesophyll to the palisade cells
Oxygen also diffuses from the palisade cells through the spongy mesophyll to the stomata
What is the function of xylem tissue?
⦁ Xylem tissue transports water from the roots to the stem and leaves and some of this water is used in photosynthesis
⦁ The xylem also transports dissolved mineral ions which are used to make proteins and allow the plant to grow?
What is the function of phloem tissue?
⦁ Phloem tissue transports dissolved sugars produced by photosynthesis from the leaves to the rest of the plant the sugars can be used in respiration or be stored as starch
⦁ The movement of sugars and other molecules through phloem tissue is called translocation
Where is meristem tissue found?
⦁ At growing tips
What is the function of meristem tissue?
⦁ Meristem tissue contain stem cells with can differentiate into different types of plant tissue
What is transpiration?
⦁ The process of water evaporating from leaves
Describe transpiration in a leaf?
⦁ Transpiration stars with the evaporation of water from cells inside the leaf
⦁ The water vapor then diffuses through the air spaces in the spongey mesophyll and out of the leaf through the stomata
⦁ Now water passes into the leaf in the xylem to replace the lost water and is drawn up by root hair cells and back into the leaf
⦁ This process is called the transpiration stream
Why is the transpiration stream important?
⦁ The transpiration stream brings water to the leaf which is required for photosynthesis
⦁ The transpiration stream also brings dissolved mineral ions such as nitrate ions which are important for the growth of the plant
⦁ The evaporation of the water from the leaf also cools the leaf down
What factors affect the rate of transpiration?
⦁ The rate of transpiration is higher at higher temperatures because evaporation is faster when temperatures are higher
⦁ Transpiration is also higher under dry conditions when the air isn’t humid because evaporation takes place quicker under dry conditions
⦁ Transpiration is also higher in windy conditions as wind removes any water vapour allowing more to evaporate
⦁ Transpiration increases when the light intensity increases because high light intensity increases the rate of photosynthesis, which causes the stomata to open and allow carbon dioxide to enter which allows water vapour to pass out of the leaf
What are stomata surrounded by?
⦁ Two guard cells
Describe how stomata and guard cells work?
⦁ When the light intensity is high the guard cells swell and change their shape which causes the stomata to open
⦁ This means that carbon dioxide can now diffuse into the leaf and be used in photosynthesis
⦁ Under hot conditions the water closes its stomata to reduce the rate of transpiration to reduce water loss, but this means that the plant can no longer photosynthesise
