Stem and Root Modifications Floral Careers Plant Propagation

What Exactly is a Stem? A stem: is generally considered to be the central axis of the plant. supports the leaves and flowers of a plant. has nodes from which new shoots and sometimes new roots can arise. is usually found above-ground, but can be modified and found below-ground as well.

Stem Modifications The following are stem modifications: Tubers Corms Bulbs Rhizomes Stolons

Tubers A tuber is an underground stem that stores food. We know a potato is a tuber because it has nodes (eyes) which produce new shoots. A potato is a tuber

Corms A corm is a swollen, vertical stem with a papery covering. Gladiolus and Crocus are examples of plants that form corms. Crocus corms

Gladiolus corms with cormels

Bulbs Bulbs come in 2 basic types: Tunicate bulbs; onions and tulips are examples. Scaly (Imbricate) bulbs; tiger and asiatic lilies are examples.

Tunicate Bulbs Tunicate bulbs have: A papery outer covering called a tunic. A compressed, modified stem with nodes, called a basal plate. Fleshy scales made of modified leaf tissue. A tunicate bulb

Tunicate Bulbs Fleshy Scales Basal Plate Onion is a tunicate bulb

Onion bulb shown in cross-section Tunicate Bulbs Tunicate bulbs form “onion rings” when cut in cross-section. Onion bulb shown in cross-section

Scaly Bulbs The other type of true bulb is a scaly bulb. Scaly bulbs: Lack a papery covering (tunic). Have a basal plate. Have fleshy scales made of leaf tissue. Do not form “onion rings” when cut in cross-section.

Scaly Bulbs Lilium is a scaly bulb

Bulb Growth Cycle

Rhizomes Rhizomes are: underground stems. horizontally-growing. produce shoots and adventitious roots. Iris rhizome

Rhizomes Some plants, like quack grass, produce long, thin rhizomes.

The pachymorph rhizome of Ginger Rhizomes Other plants, like ginger, produce large, thick rhizomes called pachymorphs. The pachymorph rhizome of Ginger

Stolons Stolons are: Aboveground stems. Grow horizontally. Produce shoots and adventitious roots. Strawberry and Spider Plant are examples of plants that produce stolons.

Stolons Wild Strawberry stolons

Root Modifications There are 2 basic types of root modifications: Fleshy Tap Roots Tuberous Roots

Fleshy Tap Roots Carrots, beets, and radishes are examples of plants forming fleshy tap roots. Carrots

Tuberous Roots Sweet potato is an example of a tuberous root. A sweet potato is a tuberous root

Tuberous Roots Dahlias are perennial bedding plants that form tuberous roots. Dahlia

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