Anatomy and Physiology Stems Student Learning Objectives Distinguish

Anatomy and Physiology – Stems!

Student Learning Objectives • Distinguish between wood and herbaceous stems. • Explain the functions of layers of a plant stem. • Distinguish between xylem and phloem.

Stem Functions • Support the plant and position stem to receive the most sunlight. • Conduct (move) water and nutrients from roots to the branches and leaves.

Stem Functions • Store food for use by plant. • Carry food manufactured by the leaves to the roots.

Herbaceous stems • Green and soft • Support comes from pressure of water in the stem tissue. – These will wilt and droop when they do not have enough water. • These are mostly annuals

Herbaceous Stems • Most row crops, forages, and vegetables have herbaceous stems. – What are row crops? – What are forages?

Woody Stems • Hard • Do not wilt with low water

Woody Stem Composition • Outermost layer is bark • Protects the plant

Bark • Divided into inner and outer sections – Outer section consists of cork cambium • Waxy, waterproof substance that keeps the inner tissues from drying out.

Cork Cambium • Contains meristematic cells – Divide and cause growth to the outer side of stem – When outer cells die, they form cork layer

Phloem • Inside of cork cambium • Tube that conducts (moves) nutrients from leaves to roots and other parts of plants • Remember, DOWN!

Phloem • Sap – Phloem fluid of high amounts of sugar – This is what maple syrup is!

Cambium • Beneath the outer and inner bark • Separate phloem and xylem • Made up of growing living cells

Xylem • Made up of tube carrying water and nutrients from roots. • Xylem is what forms growth rings in trees. • Remember, UP!

Xylem • Water and nutrients are transported to the outer part of trees only. • Inner part of tree is dead. • Xylem is also dead and hollow cells.

Xylem and Phloem • Xylem – Transport through tracheids • Phloem – Transport through sieve tubes

Xylem & Phloem in Herbaceous Stem

What Questions Do You Have? ? ?

Pop Quiz 1. What vessel transports water and nutrients from root to leaves? 2. What structure provides protection for plant stems? 3. What makes herbaceous and woody stems stand rigid?