ALLELOPATHY among species of the lower Sonoran Desert

Introduction:

Plants, like animals, are extremely complex chemical factories. These complexities are the result of evolutionary changes that promote survival. Some methods of defense include the production of chemical scents and nutrients to encourage or attract pollinators such as bees. Other methods include the production and storage of poisons which discourage consumption by herbivores/omnivores as well as parasitic attack. Plants rely on ground nutrients and photosynthesis - sun exposure – to create the fuel they need to survive and grow. As such plants must compete with other plants for sunlight, soil nutrients, and water. Since plants do not possess the ability to flee competitive adversaries they have adopted means of chemical combat. One method of reducing the competition is to simply prevent it from sprouting in the first place.  This method is known as allelopathy, a system in which one species of plant produces chemicals that effectively prevents the germination and growth of adjacent plants.

When this type of  chemical warfare is used against  plants within the same species it is known as intraspecific competition,  when it is used against plants of a different species it is known as interspecific competition.

Some of the ways plants may release allelopathic substances into their surrounding environment:

1.     Directly into the soil via their root system

2.     Chemicals may be washed off of leaves during rain

3.     Chemicals may blow into the air which are then are deposited on the soil or the surface of other plants when dew forms.

4.     Leached from living or dead shoots into surrounding soil

In today’s laboratory experience we began the initial stages of our project. Our first step was locating information on the optimal germination environment for the plants that we are going to be growing. This process involved a great deal of internet research and an attempt at contacting some of the state’s agricultural centers, including the Desert Botanical Gardens, ASU and UA Cooperative Extension.

The seeds we will be germinating include:

Ambrosia deltoidea (triangle bursage)

Cercidium microphyllum (palo verde)

Larrea tridentata (creosote bush)

Encelia farinosa (brittlebush)

Cylindropuntia acanthocarpa (buckhorn cholla)

Phacelia campanularia (desert bluebell)

Opuntia phaeacantha (prickly pear)

Eschscholzia Mexicana (golden poppy)

Sphaeralcea ambigua (desert globemallow)

Lupines arizonicus (Arizona Lupine)

Lesquerella gordonii (bladder pod)

Carnegiea gigantea (saguaro)

Today was a day of preparation. We labeled our petri dishes, prepared paper towel mediums, counted seeds and placed them in their appropriate petri dishes. No solutions were added.