Stem and Root Modifications Floral Careers Plant Propagation

Stem and Root Modifications Floral Careers Plant Propagation

What Exactly is a Stem? § Before we go any further in this presentation, let’s define a stem. § A stem: l l 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: l l l Tubers Corms Bulbs Rhizomes Stolons

Tubers A potato is a tuber § 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.

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

Corm Growth Cycle

Gladiolus corms with cormels

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

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

Tunicate Bulbs Fleshy Scales Basal Plate Onion is a tunicate bulb

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: l l Lack a papery covering (tunic). Have a basal plate. Have fleshy scales made of leaf tissue. Do not form “onion rings” when cut in crosssection.

Scaly Bulbs Lilium is a scaly bulb

Bulb Growth Cycle

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

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

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

Stolons § Stolons are: l l 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: l l 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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