Plant organisation

• Plant cells, tissues and organs are adapted to their functions.
• The stem, root and leaves form an organ system that transports substances into, around and out of a plant.
• The main roles of plant stems and roots are to transport substances around.
• Xylem transports water and minerals.
• Phloem transports sugars and amino acids dissolved in water.
• These are distributed differently in roots and stems.
• In the root, the xylem forms a central column.
• The phloem is towards the centre, outside the xylem.
• In the stem, the transport tissues of the xylem and phloem are grouped into vascular bundles.
• Any part of a plant above ground, where it is exposed to light, can photosynthesise.
• Plant leaves are the main organ of photosynthesis.
• Plant leaves are adapted for gas exchange and photosynthesis.
• Large surface area for maximum absorption of light; for optimum absorption of carbon dioxide.
• A thin, flattened blade so that water and gases have a limited distance to diffuse.
• Vascular tissue in the midrib and veins for transporting water and minerals to the leaf; branches of the phloem for transporting glucose and other products of photosynthesis to other parts of the plant.
• Air spaces between cells within the leaf for the diffusion of gases.