Stem and Root ModificationsFloral Careers Plant Propagation

What Exactly is a Stem?Before we go any further in this presentation, lets define 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 ModificationsThe following are stem modifications:TubersCormsBulbsRhizomesStolons

TubersA 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

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

Corm Growth Cycle

Gladiolus corms with cormels

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

Tunicate BulbsTunicate 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 BulbsFleshy ScalesBasal PlateOnion is a tunicate bulb

Tunicate BulbsTunicate bulbs form onion rings when cut in cross-section.Onion bulb shown in cross-section

Scaly BulbsThe 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 BulbsLilium is a scaly bulb

Bulb Growth Cycle

RhizomesRhizomes are:underground stems.horizontally-growing.produce shoots and adventitious roots.

Iris rhizome

RhizomesSome plants, like quack grass, produce long, thin rhizomes.Quack Grass

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

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

StolonsWild Strawberry stolons

Root ModificationsThere are 2 basic types of root modifications:Fleshy Tap RootsTuberous Roots

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

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

Tuberous RootsDahlias are perennial bedding plants that form tuberous roots.Dahlia

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