Root and stem of a dicot plant: Stem

• The stem holds leaves, flowers and fruit in a favorable position.
• The stem transports the organic substances from the leaves.
• Stems store and reserves nutrients.
• The stem assists with photosynthesis, pollination and distribution of seeds.
• The external structure of the stem includes:

  Nodes and internodes

  Terminal buds

  Axillary buds
• Nodes are where leaves and side branches develop.
• Internodes are the spaces in between nodes
• Terminal buds consist of meristematic tissue which allows for primary growth.
• Axillary buds occur in axils and develop into lateral branches.
• The internal structure of a stem includes:

  Epidermis

  Cortex

  The central cylinder
• The Epidermis consist of thin brick shaped cells that form the outside of the stem. Some epidermal cells are stomata. The epidermis is covered in a waterproof cuticle and hair growth may occur.
• The Cortex is the layer directly under the epidermis and consists of:

  Collenchyma

  Parenchyma

  Endodermis
• The Collenchyma is a layer under the epidermis consisting of cells with thickened cell wall corners.
• The Parenchyma is made of layers of large, thin walled cells with large intercellular spaces.
• The Endodermis is a the inner most layer and is a single layer of brick shaped cells . Starch is stored in the starch sheath .
• The Central cylinder consists of the vascular tissue in forms of bundles.
• Vascular bundles consist of:

  Xylem(outside)

  Phloem(inside)

  Sclerenchyma cap(dead cells)

  Cambium ( layer between xylem and phloem)
• The parenchyma that occurs between vascular bundles is called the medullary and it transports substances between the pith and the cortex.
• The Epidermis protects underlying tissue.
• The Cuticle prevents loss of water
• The stomata allow gaseous exchange
• Collenchyma supports and strengthens the stem and allows photosynthesis.
• The parenchyma stores organic substances and allows for gaseous exchange.
• The endodermis stores starch
• The sclerenchyma fibers protect vascular bundles and strengthens and supports the stem
• The Xylem transports mineral salts and water
• The Phloem transports manufactured organic substances
• The cambium makes secondary thickening possible