stem and root modifications floral careers plant propagation
TRANSCRIPT
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:
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
Corm Growth Cycle
Gladiolus corms with cormels
Bulbs
Bulbs come in 2 basic types: Tunicate bulbs; onions and tulips are examples. Scaly 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
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.
Quack Grass
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
End