Presentation on theme: "Stem and Root Modifications Floral Careers Plant Propagation."— Presentation 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: l is generally considered to be the central axis of the plant. l supports the leaves and flowers of a plant. l has nodes from which new shoots and sometimes new roots can arise. l is usually found above-ground, but can be modified and found below-ground as well.
Stem Modifications §The following are stem modifications: l Tubers l Corms l Bulbs l Rhizomes l 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: l Tunicate bulbs; onions and tulips are examples. l Scaly bulbs; tiger and asiatic lilies are examples.
Tunicate Bulbs §Tunicate bulbs have: l A papery outer covering called a tunic. l A compressed, modified stem with nodes, called a basal plate. l 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: l Lack a papery covering (tunic). l Have a basal plate. l Have fleshy scales made of leaf tissue. l Do not form “onion rings” when cut in cross- section.
Scaly Bulbs Lilium is a scaly bulb
Bulb Growth Cycle
Rhizomes §Rhizomes are: l underground stems. l horizontally-growing. l 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: l Aboveground stems. l Grow horizontally. l Produce shoots and adventitious roots. l 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 Fleshy Tap Roots l 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