Understanding Stem Anatomy

Understanding Stem Anatomy

•Describe the functions of a stem.

•Recognize the external structures of a stem.

•Analyze the internal structures of a stem.

•Distinguish between the different types of specialized stems.

What are the functions of a stem?

• Responsible for the size and shape of a plant

• Made of different materials– Wood– Herbaceous or soft

What are the functions of a stem?

• Support the leaves • Move water, minerals, and food throughout

the plant– Translocation

• Help produce food through photosynthesis• Store food that has been manufactured

What are some of the structures on the outside of a stem?

• Terminal bud – Growing point at the tip of the stem

• Lateral bud– Side bud on the stem

• Node– Where the leaf is attached to the stem

• Internode – The area between leaves

• Leaf scar– Scar where leaf falls off of the stem

• Bud scale scar– Scar left behind from last year’s growth

• Lenticels– small spots on the stem that allow exchange

gases with its environment

What are some of the structures

on the outside of a

stem?

What are some of the structures inside a stem?

• Two ways interior stem tissue is organized– Scattered bundles

• found in monocots.

– Rings• found in dicots.

What are some of the structures inside a stem?

• Three important internal tissues– Xylem

• Transports the water and minerals throughout the plant

• Found closer to the center of the stem

– Phloem• Transports food that is produced in the leaf

to the rest of the plant• Found toward the outside of the stem

– Cambium• Responsible for the production of new

xylem and phloem• Causes growth in girth of the stem • Found between the xylem and the phloem

How can we use the internal structure of a tree stem?

• Heartwood – Darker wood to the center of the tree– Provide strength and no longer function in

conducting materials

• Sapwood – Lighter wood circling the heartwood – Actively conducts water and dissolved minerals

How can we use the internal structure of a tree stem?

• The age of a tree can be determined by counting annual growth rings. – Rapid growth (spring and early summer) =

large cells with thin walls = large in diameter– Slow growth (mid-to-late summer) = smaller

cells and have thicker walls

What are some different kinds of specialized stems?

• Bulb – Very short flattened stem that has

several fleshy leaves attached to it– found beneath the soil – Example = onion

• Corm – A spherical structure– Entire structure is stem– Example = gladiolus

What are some different kinds of specialized stems?

• Rhizome – A thick underground stem that

lies horizontally– Example = Hostas and Mother-

in-law’s Tongue– Tuber

• A swollen tip that stores food• Example = Irish potatoes

• Stolon – A horizontal stem that lies above

the ground that are involved in the spreading of the plant

– Example = Strawberries

What are some

different kinds of

specialized stems?