Plant tissues, organs and systems

What are plants made of ?

Organs like stems and roots and leaves

What do plant organs work together to do ? What can this do?

Plant organs work together to make organ systems. These can perform various tasks that a plant needs to carry out to survive and grow.

What is the epidermal tissue ?

• covers the whole plant. They have a waxy cuticle which helps reduce water loss by evaporation

What is the Xylem and Phloem ?

• Transport things like water, mineral ions and food around the plant. They form a network of vascular bundles which transfer water and other nutrients to the rest of the leaf and take away the glucose produced by the rest of the leaf. They also help support the whole structure

What is the Meristem tissue ?

• Found at the growing tips of shoots and roots and is able to differentiate into lots of different types of plant cell allowing the plant to grow.

What is the spongy mesophyll tissue ?

• In the leaf and contains big air spaces to allow gases to diffuse in and out of the cell

What is the palisade mesophyll tissue ?

• Part of the leaf where photosynthesis takes place

How is the epidermal tissue adapted to cover the whole of the leaf ?

It has a waxy cuticle which helps reduce the rate of water loss by evaporation

How is the palisade mesophyll tissue adapted for photosynthesis?

It has lots of chloroplasts meaning they are near the top of the leaf where they can get the most light

How are the xylem and phloem adapted to transport stuff?

They form a network of vascular bundles which deliver water and other nutrients to the entire leaf taking away glucose by photosynthesis. They also help support the structure.

What are tissues of leaves adapted for ?

Efficient gas exchange

What do air spaces in the spongy mesophyll do ?

Increases the rate of diffusion

What are phloem tubes ?

They transport food. They are made of collumns of elongated living cells with small pores in their end walls to allow cell sap to flow through.

They transport food substances, mainly dissolved sugars, made in the leaves to the rest of the plant for immediate use or for storage.

This transpprt goes in both directions.

This process is called is called translocation ( the movement of dissolved sugars around a plant).

What is translocation?

The movment of dissolved sugars around a plant

Xylem tubes

Made of dead cells joined to end with no end walls between them and a hole down the middle. They are strengthened with a material called lignin. They carry water and mineral ions from the roots, to the stems and leaves

What is the transpiration stream?

The movement of water from the roots, through the xylem and out of the leaves

What are the factors affecting the transpiration rate ?

• Light intensity - The brighter the light the greater the transpiration rate. Stomata begin to close as it gets darker. Photosynthesis cant happen in the dark meaning they dont need to open to let CO2 in. When the stomata are closed very little water can escape.

• Temperature - The warmer it is the faster the transpiration rate. When its warm the air particles have more energy to evaporate and diffuse out of the stomata.

• Humidity - the drier the air around a leaf, the faster transpiration happens. If the air is humid then their is lots of water in it already meaning their isnt much difference between the inside and outside of the leaf.

how are guard cells adapted to opens and close the stomata ?

They have a kidney shape which opens and closes the stomata. Thickened inner walls and thin outer walls make the opening and closing work.

How are guard cells adapted for gas exchange ?

When the plant has lots of water the guard cells fill with it and become turgid. This causes the stomata to open allowing gases to be exchanged by photosynthesis

How do guard cells control water loss ?

• When the plant is short of water the guard cells fill with it and become flaccid.. This makes the stomata close stopping water vapour escaping

• They are also sensitive to light and close at night without losing out on photosynthesis.

Why do you usually find more stomata on the undersides of the leaves than the top?

The lower surface is cooler so less water is lost through the stomata than if they were on the upper surface