Plant cell organisation

In a nutshell

Plant cells are organised into tissues and organs, just like animals. The leaf is the site of photosynthesis and gas exchange in plants.

Plants

In a plant, several organs work together and form an organ system. The leaves, stems and roots are all organs which work together to transport important substances around the plant. These plant organs are made from various tissues which have specific properties:

Tissue	Property
Xylem and phloem	These transport substances around the plant. Examples Water, minerals and food.
Palisade mesophyll tissue	This is where most photosynthesis occurs. It is a part of the leaf.
Spongy mesophyll tissue	This has large air spaces, allowing gases to diffuse into and out of the cells. It is also a part of the leaf.
Epidermal tissue	This covers the entire plant.
Meristem tissue	This is located at the growing tips of the roots and shoots.

Leaf structure

The leaf is the site of photosynthesis and gas exchange in the plant. The structures of tissues in the leaf all have an important function:

Biology; Organisation; KS4 Year 10; Plant cell organisation

	Adaptation	Description
1.	Transparent waxy cuticle	Also allows light to pass through to the chloroplasts.
2.	Transparent epidermis cells	Allows light to pass through to the chloroplasts.
3.	Tightly packed mesophyll cells	Palisade mesophyll cells are located at the top of the leaf and they contain lots of chloroplasts which maximises photosynthesis.
4.	Spongy mesophyll	The spongy mesophyll contains air spaces (8.) which increase the rate of diffusion of gases.
5.	Phloem	The phloem tubes transport the glucose that is made during photosynthesis away from the leaf.
6.	Xylem	The xylem tubes transport water from the roots to the leaf for photosynthesis.
7.	Stomata	These pores allow carbon dioxide to diffuse into the leaf from the air and oxygen to diffuse out of the cells.

The leaf is also thin, this allows air to surround most of the cells. This means gas exchange can take place over a larger surface area.