Plant Revision

Xylem: -Transports water and soluble materials.

Phloem: -Transports sugars.

                                                                      Root

• The vascular bundle is found in the centre.
• The arrangement provides strength to withstand the pulling forces to which roots are exposed/
• Around the vascular bundle the cells are called the endodermis - they help to get water into the xylem vessels.
• Inside the endodermis is the pericycle: contains meristem cells that can divide.

                                                                          Stem

• The vascular bundles found near the outer edge of the stem. 

• Xylem is found towards the inside of each vascular bundle; phloem is found towards the side.

• In between the xylem and phloem is a layer of cambium.

• Cambium is a layer of meristem cells that divide to make new xylem and phloem.

                                                                     Leaf

• A dicotyledon leaf has a branching network of veins that get smaller as they branch away from the midrib.

                                                         Structure of Xylem

• Consists of tubes for water, fibres for support and living parenchyma.

Xylem Vessels

-Long cells with thick walls containing lignin.

-Lignin waterproofs walls of cells and strengthens them.

-Cells die and end decay, forming a long tube

-Lignin forms spiral, rings or broken rings.

-Some lignification is not complete, and pores are left called pits, allowing water to move between vessels.