AY Honors/Grasses/Answer Key

3. About how many species around the world are there in the grass family called Gramineae or Poaceae?

The Poaceae is also known as the Gramineae. There are about 600 genera and between 9,000 to 10,000 species of these plants. Plant communities dominated by Poaceae are called grasslands; it is estimated that grasslands comprise 20% of the vegetation cover of the earth. This family is the most important of all plant families to human economies: it includes the staple food grains grown around the world, lawn and forage grasses, and bamboo, widely used for construction throughout Asia.

4. Do the seeds of grasses have two halves as does the bean (a dicotyledon), or does the seed consist of just one part as do the lily, date, and coconut (monocotyledons)?

All grasses are monocotyledons, so the seeds have only one part.

5. What unique characteristic in the growth of grass leaves makes it possible for the plant to flourish even though continually mowed or grazed?

Grasses add new growth to the bottom of the plant rather than to the top, so when the tops of the grass blades are removed by mowing or by grazing, the plant continues to grow.

6. Name three annual grasses, that is, grasses that sprout from seeds, blossom, bear seeds, and then die the same summer.

• Barnyard grass (Echinochloa crus-galli)
• Crabgrass (Digitaria spp.)
• Common wild oat (Avena fatua)
• Foxtail grass (Alopecurus spp.)

7. Name three perennial grasses, that is, grasses whose roots live on from year to year, although the top dies down to the crown each autumn.

• Nutsedge (Cyperus)
• Couch Grass (Elytrigia repens)
• Panicum (Panicum spp.)
• Fescue (Festuca spp.)
• Kentucky bluegrass (Poa pratensis)

8. In each of the following cases name a single grass, or more where indicated, from which the product is made:

a. Bread (three grasses)

• Wheat
• Rye
• Barley
• Oats