Tag Archives: petals

OS16 Female Pumpkin Flowers

Investigation 15 looked at the male pumpkin flower. It only produces pollen, no pumpkins. The female pumpkin flower can grow into a pumpkin. Remember to pick your flower early in the morning and put the stem into a cup of water. Let’s look at a female flower.

Question: What parts are in a female flower?

female pumpkin flower

Materials:

Female Pumpkin Flower

Metric ruler

Knife

Magnifying glass

Procedure:

Step 1: Open your Science Journal, write “Investigation 16” and the date.

Step 2: Examine the outside of the female flower. Measure how tall it is. Compare it to the diagram of a flower on page 101 and label your drawing with the parts you see.

Step 3: Smell the inside of the flower.

Step 4: Carefully cut or tear the petals off the flower.

outside pumpkin petal

Three green veins go up the outside of each of the five lobes of a pumpkin flower. Only the tops are orange.

Step 5: Examine the petals. Compare the inside and outside surfaces [look, color, feel etc.].

Step 6: Examine the inside of the female flower. Measure the pistil. Touch the pistil. You can safely taste the liquid on the pistil. Draw and describe what you observe.

pumpkin flower pistil

Isolated from its flower a pumpkin flower pistil is a bumpy wet mound.

Step 7: Examine how the pistil joins the ovary [tiny pumpkin].

Step 8: Carefully slice the pistil and ovary in half lengthwise. Examine what you see in the two halves. Draw what you see.

pumpkin flower ovary longitudinal cut

Each line of ovules extends down the length of the pumpkin ovary. Each ovule has the potential to become a pumpkin seed.

Step 9: There should be a line of ovules or tiny seeds showing in the ovary. If there isn’t, cut a thin slice off the ovary to find a line of ovules.

Step 10: After you examine the line of ovules, cut across that half of the ovary and look for where lines of ovules are.

Observations:

Describe a female pumpkin flower

Label the parts on your drawing

Describe the outside of the petals

 

inside pumpkin flower petal

Inside a female pumpkin flower petal each main vein stands out in green against a pale yellow background. Only the tops of the petals are orange.

Describe the inside of the petals

 

split pumpkin pistil

Split in half its easy to see the single pistil isn’t single at all but several pistils clumped together.

Describe the pistil.

Describe the tiny pumpkin.

Describe how the inside of the pistil and ovary join

Describe the ovules

Number of ovules in one row:

Number of rows of ovules in half the ovary:

Number of ovules in half the ovary:

Number of ovules in the ovary:

Analysis:

Multiply the number of ovules in a row by the number of rows in half an ovary.

Multiply the number of ovules in half an ovary by two for the number of ovules in an ovary.

Conclusions:

If all the ovules in an ovary become seeds, how many seeds will there be in the pumpkin?

 

pumpkin flower ovary cross section

Each line of ovules is inside a spiral arm. Each half of an ovary has three lines of ovules.

If every ovule must join with one grain of pollen to become a seed, how many grains of pollen must be carried by insects to the pistil?

Why do you think the pistil is wet and sticky?

 

enlarged pumpkin pistil

Magnified a pumpkin pistil has many bumps making its surface look grainy.

What do you think makes the pistil wet and sticky?

 

OS15 Male Pumpkin Flowers

Pumpkins have two kinds of flowers. One flower makes pollen and is called a male flower. Most flowers on a pumpkin plant are male flowers. These have long thin stems called petioles. On the day you want to do this Investigation, go out early in the morning and pick a male flower. It may have insects in it. Use a long grass stem to push them out. Don’t knock the flower about, especially upside down or all the pollen will fall out! Put the flower into a glass of water until you are ready to look it over. It will wilt in just a few hours so let’s start early and find out about a male flower.

 

Question: What parts are in a male pumpkin flower?

Materials:

Male Pumpkin Flower

male flower

A male flower has a long, slim petiole. They rise up from leaf nodes, places where the leaf petioles join the pumpkin vine.

Metric ruler

Knife

Magnifying glass

Microscope

Slide and coverslip

 

Procedure:

Step 1: Open your Science Journal, write “Investigation 15” and the date.

Step 2: Examine the outside of the male flower. Measure how tall it is. Compare it to the diagram of a flower and label your drawing with the parts.

inside male flower

Looking inside a male flower it is easy to see the flower has five petals joined together. The stamens are joined into a single column. Around the base of the column is a trough evidently filled with nectar as insects congregate there. Larger insects would come in contact with the pollen on the stamen column getting it on their bodies so the pollen will be carried off when the insect leaves hopefully stopping by a female flower next.

Step 3: Smell the inside of the flower.

Step 4: Carefully tear or cut off the petals of the flower and lay them out on the table.

Step 5: Examine the petals. Compare the inside and outside surfaces – look, color, feel.

Step 6: Examine the stamen. Measure the stamen. Touch the stamen. Draw and describe what you observe.

stamen

Splitting a stamen lengthwise shows the inside is solid. The yellow concentric loops form a thin skin on the outside of the top half of the stamen.

Step 7: Put a drop of water on a slide. Put some of the pollen from the stamen on the water. Put on the coverslip.

Step 8: Examine the pollen with the microscope.

Step 9: Carefully slice the stamen in half lengthwise and examine the inside.

magnified stamen

Magnifying the top of the stamen shows the concentric loops are yellow ridges on a pale base.

Observations:

Petals

male flower petals

The inside of the joined petals is smooth, slick, changing from yellow at the bottom to orange at the top. Large veins run down the center of each petal. The flower wilts quickly after being picked.

outside male flower petals

From the outside the joined petals are more greenish yellow at the base but still orange at their tops. Three veins are obvious on each petal lthough only the middle one is really big on the inside. The petals still feel smooth but don’t have a slick feel.

Conclusions:

Explain why you think a pumpkin flower has only one or has many petals joined (fused) together.

If a pumpkin flower has fused petals, how many petals are there? How can you tell?

What advantages would fused petals instead of separate ones give a pumpkin flower? (You might want to look at some flowers on your pumpkin plant in the early morning to get some ideas.)

Each seed in a pumpkin flower needs one grain of pollen to become a seed. Why are there so many more male flowers making pollen than female flowers (These have tiny pumpkins under them.)?

Why do you think the flower makes so much pollen since only one grain or piece is needed for each seed?

male flower stamen

The large stamen has a big base with three feet. It sits in the center of a moat. The five sepals and petals are on the outside edge of this moat. The top of the stamen looks like an unexpanded mushroom but with concentric loops all over it. Pollen is found in the troughs of the loops.

Many flowers have lots of little stamens. A pumpkin flower seems to have only one. Does the pumpkin flower have fused stamens? Explain why you think so.

Different kinds of plants have pollen grains (separate pieces of pollen) with different shapes. Archeologists use fossil pollen to identify the kinds of plants that grew in an area long ago. What special things about a pumpkin pollen grain do you see?