StemsPart IV

Rhizomes and Stolons

Types of underground stems

• Besides tubers, corms and bulbs there are structures that look like regular stems but are found underground

»Rhizomes

Rhizomes

Definition• An underground,

horizontal stem that spreads and propagets a plant. The leaves are reduced to scales. Rhizomes often have roots.

Roots on Rhizomes or other kinds of stems are called adventitous roots.

How are they different from corms, tubers and bulbs?

• They do not store food.

• They connect plants to one another

Some common plants with Rhizomes

Jerusalem Artichoke

Sweet Potato

Dahlias

IrisGinger

Grasses like Phragmites and Bamboo

• Whole fields are often interconnected

Another type of horizontal stem is a Stolon

• They grow at or just above the surface of the ground. They give rise to a new plant at its tip or from axillary branches (branches that come of the sides of the stem).

Unlike rhizomes they are above ground

Lots of plants called runners have stolons

Stolons can occur on vines if the vines spread over the ground or

even on the surface of waterPartridge Berry

Bulbs, Corms, Tubers, Rhizomes and Stolons

• All forms of asexual reproduction– All plants formed by these structures are Clones!

• How would this type of reproduction be advantageous to people who sell plants?

Can you force a plant stem to act like a stolon?

• Yes– The method is called layering. If you can force

roots to grow from a stem, you have layered that stem.

– Once it has roots you can cut it free from the original plant.

Bend a stem down to the ground and bury it with the tip pointing up to layer. You will have to water more than usual at the site of layering to get roots to form.

Disadvantages• Layering can take a long time to work.• Some plants will not layer and stems will rot.

Advantages• Some plants naturally layer and multiply fast

in this way (black raspberry)• Some plants that are difficult to root in from

cuttings can be propagated in this way.

Homework

• Find 2 examples of plants with Stolons and 2 with Rhizomes

• Read pages 121 – 123 (Simple layering) in Reiley & Shry.

Economically Important Plants of the World

• Your Thanksgiving Assignment is to present to the class information on economically important plants from a country of interest (perhaps your country of origin).

• Find out how it is cultivated• Find out where it originated from• Find out how it arrived in that country if it is not native• Find out how important it is to the country• Find out how it is used (is it eaten? How is it prepared?)

• You can start your research here:• http://www.state.gov/• Type country of interest in search field