Presentation on theme: "Stem and Root Modifications"— Presentation transcript:
1 Stem and Root Modifications Floral Careers Plant Propagation
2 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.
3 Stem Modifications The following are stem modifications: Tubers Corms BulbsRhizomesStolons
4 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
5 Corms A corm is a swollen, vertical stem with a papery covering. Gladiolus and Crocus are examples of plants that form corms.Crocus corms
8 Bulbs Bulbs come in 2 basic types: Tunicate bulbs; onions and tulips are examples.Scaly bulbs; tiger and asiatic lilies are examples.
9 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
10 Tunicate BulbsFleshy ScalesBasal PlateOnion is a tunicate bulb
11 Onion bulb shown in cross-section Tunicate BulbsTunicate bulbs form “onion rings” when cut in cross-section.Onion bulb shown in cross-section
12 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.