Plant tissues, organs and systems - PMT

How is epidermal tissue adapted for its function?

Epidermal tissue covers the entire plant. It has a waxy cuticle which helps reduce water loss from the leaf surface.

How is palisade mesophyll tissue adapted for its function?

Palisade mesophyll tissue contains lots of chloroplasts which allows photosynthesis to progress at a rapid rate.

How is spongy mesophyll tissue adapted for its function?

Has lots of air spaces which allows gases to diffuse in and out.

How is xylem adapted to its function?

● Made up of dead cells which form a continuous hollow tube - allows the movement of water and mineral ions from the roots to the leaves.

● Strengthened by lignin - makes the vessel strong and waterproof.

● Has bordered pits - allow minerals to be transported to specific places.

How is phloem adapted for its function?

● Made up of elongated living cells.

● Cells have sieve plates that connect them

together - cell sap can move through plates

into other cells.

● Sieve tube cells have few organelles to allow

the efficient transport of substances.

How is meristem tissue adapted for its function?

Made up of stem cells which can differentiate into many different cell types, allowing the plant to grow.

What tissues does the leaf contain?

- Epidermis

- Palisade mesophyll

- Spongy mesophyll

- Xylem cell

- Phloem cell

- Guard cell

What is the function of guard cells?

Guard cells control the opening and closing of the stomata, according to the water content of the plant.

How are stomata adapted for their function?

Stomata allow the control of gaseous exchange and water loss from the leaf.

● More stomata on the base of the leaf - minimises water loss as this side is cooler and shaded.

● Have guard cells which control their opening and closing.

How are root hair cells specialised?

Root hair cells allow the uptake of water and mineral ions from the soil. They have a large surface area to maximise the rate of absorption and contain lots of mitochondria to release energy for active transport of mineral ions.

What is translocation?

The movement of dissolved sugars from the leaves to the rest of the plant

What is transpiration?

the evaporation of water vapour from the surface of the plant

How does transpiration work?

● Water evaporates from the leaf surface via the stomata.

● Water molecules cohere together - more water is pulled up the xylem in an unbroken column.

● More water is taken up from the soil - creating a continuous transpiration stream.

How does temperature affect the rate of transpiration?

Increasing the temperature increases the rate of transpiration. Higher rate of evaporation and diffusion of water - therefore rate of transpiration is increased.

How does humidity affect transpiration?

Increased humidity decreases the rate of transpiration. High humidity reduces the water vapour concentration gradient so rate of evaporation decreases, meaning rate of transpiration decreases.

How does wind speed affect the rate of transpiration?

Increased wind speed increases the rate of transpiration. Increased air movement lowers water vapour concentration outside of the leaf. This increases the water vapour concentration gradient, so increases the rate of evaporation and transpiration.

How does light intensity affect the rate of transpiration?

Increased light intensity increases rate of transpiration. The rate of photosynthesis increases, so more stomata is open. This increases the rate of evaporation and transpiration.