Wednesday, May 6, 2009

Lab: Daffodil Dissection

We are moving from human anatomy to plant anatomy. This week in lab we will be starting our (short) unit on plants and plant anatomy. This lab will begin with a short discussion on dichotomous keys. After that, students will dissect a daffodil and answer questions about the parts of a flower.





Daffodil Dissection

a. Safety

i. If using sharp scissors, only use when told; don’t wave them around. If using scalpel (very sharp), only use when told; make cuts carefully with blade down on the paper paper towel and fingers out of the way

b. Stem—use scissors to cut through the flower stem in various directions: across,

up, diagonal, and compare with each other. What do you see?

Cut Across

Cut Diagonal

Cut Up












c. Line up the stem slices on a paper paper towel.

i. What is the xylem used for?

ii. What is the phloem used for?

iii. The stem stores surplus food for growth during the season and overwinter to support new growth in the spring.

iv. Bulbs are modified stems and also store food for the plant.

d. Does your daffodil have sepals? (the outer ring of flower parts, usually green,

that protects the young flower bud) Circle YES or NO

i. In daffodils the sepals are fused to the outer flower petals.

ii. Do the outer petals look different than the inner ones? How?

iii. When sepals and petals look similar they are called tepals. Does your flower have tepals?

e. How many petals does your daffodil have?

Number of inner petals:

Number of outer petals:

i. Notice that the bottoms of the petals (or tepals) and the cup are fused together. This is called the flower tube.

ii. Use your fingers to pull off each petal or cut them off with your scissors.

iii. Line up the petals on your paper paper towel.

f. Use your scissors or fingers to cut down the sides of the cup and remove the cup.

i. What is the purpose of the flower petals and cup?

g. The reproductive part of the flower is what you have left.

i. Look at the stamen. Is this the male or female part of the flower?

1. How many stamens can you count? On a daffodil the stamens are all of the stalks except for the taller, different one in the center.

2. Stamens consist of two parts, what are these?

3. What do filaments do?

4. What do anthers do?

5. Draw and label one of the stamen of your daffodil.

6. How many stamens does your flower have?

7. Use your tweezers, scissors or fingers to remove the stamens on your flower. Try to leave the taller, center female part of the flower.

8. Touch the stamens and see if any pollen comes off and sticks to your finger. Why are stamens sticky?

9. Line up the stamens on your paper towel.

ii. Look at the female part—the pistil or carpel.

Draw the female part and label the following structures: Stigma, Style and Ovary.

a. Cut the female part open diagonally. What do you see?

Microscopes:

Either draw or describe what you see for each of the following parts of the plant. You will be graded on your descriptions.

Inside of the stem.

Make sure to state if you are looking at an up, across or diagonal cut




.

Outer Petal





Stamen






Pistal






Perfect flowers—have all the standard parts including male and female organs. Are

daffodils perfect flowers?

This lab was adapted from DaffodilUSA

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