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Plant organisation

Plant organisation

Plant cells are organised into tissues.

Plant organs are made of tissues.

The stem, root and leaves form an organ system.

These organs must function together to ensure the plant gets all it needs to survive and grow into a mature plant.

Organ system transports substances into and out of a plant.

They have two types of transport systems - xylem and phloem.

Xylem transports water and minerals from the roots to the shoots and leaves.

Phloem transports sugars and amino acids dissolved in water.

The structure of a leaf

The leaf tissues are adapted for efficient gas exchange and photosynthesis.

The broad green leaves of plants provide a large surface area for maximum absorption of light.

Thin leaf shape so that water and gases have a limited distance to diffuse.

Leaves have veins that support the structure of the leaf and transport water and minerals to the leaves.

Stomata are small holes on the underside of the leaf which allow gases to diffuse in and out.

Palisade Layer is made up of palisade cells which contain chloroplasts.

The palisade mesophyll layer of the leaf is adapted to absorb light efficiently.

In the leaf, there is a spongy layer of irregularly shaped cells with air spaces between them for efficient gas exchange.

xylem

Xylem vessels are hollow tubes or lumen.

The xylem cell walls are made from cellulose.

The cell walls in xylem vessels contain a substance called lignin which strengthens the cells and support the plant.

The flow of water through the xylem from the roots to the leaf is called the transpiration stream.

The xylem tissue transports water and mineral from the roots to the stem and leaves.

The transpiration stream only flows in one direction - up through the plant.

Transport in the xylem does not require energy. It is a physical process.

Phloem

Phloem tubes are made up of columns of living cells, called sieve tube elements.

The phloem tubes moves food substances like sugar and amino acids to every part of the plant.

Transport of substances in the phloem is called translocation.

The phloem system allows transportation in both directions.

Phloem tubes are sometimes called sieve tube elements.

The phloem cells contain a little cytoplasm, but no nucleus.

The phloem cells can't survive on their own, so each has a companion cell.

Transport of substances in the phloem requires energy.

Plants absorb minerals from the soil through their roots.

Plants need lots of water for their internal transport systems , photosynthesis and to keep cells turgid.

Water enters the root hair cells by osmosis.

Root hair cells have large surface area for absorbing water and mineral ions.

Root cells have thin walls that reduces the distance for water transfer in osmosis.

Mineral ions can be absorbed through the hairs of the root cells.

Cells have a large permanent vacuole to absorb and store as much water as possible.

Plants need to take up water and minerals from the soil and transport them to the leaves for photosynthesis.

The root hairs will naturally absorb water by osmosis, as long as the water concentration in the soil is higher.

Plants make their food through a process called Photosynthesis.

Photosynthesis is a chemical process that occurs in every green plant.

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