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
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.