In a previous exercise, you observed the flower and its many parts. You were also introduced to the events leading up to the fertilization of the egg by the sperm. The resulting cell was called the zygote. This develops into the embryonic plant. Plants also produce a second sperm cell that fuses with the polar nuclei to form a triploid endosperm. The endosperm accumulates much storage material that is used for the development of the embryonic plant. The embryo and the endosperm reside in the ovule and together these constitute a SEED. Of course the seed is contained within the ovary of the carpel; the gynoecium will develop to form a FRUIT surrounding the seeds. Today you will study the seed and fruit of the flowering plants
The ENDOSPERM starts developing immediately after double fertilization, forming a parenchymatous tissue between the nucellus tissues of the ovule and the young embryo. The endosperm divides actively during early development of the seed; later it may store considerable amounts of food material, or it may transfer the food materials to the cotyledon(s) of the embryo and disappear completely. Meanwhile, the zygote undergoes a regular sequence of divisions to form an EMBRYO organized into a central hypocotyl with ROOT APEX (radicle) at one end and one or two COTYLEDONS and small SHOOT APEX at the other. The integument(s) of the ovule become(s) modified to form the SEED COAT. The entire structure--seed coat, endosperm if still present, and embryo--constitutes the SEED and is shed from the parent plant at maturity. The seed usually can withstand quite adverse conditions and remain dormant for considerable periods of time. It serves to disseminate the species.
Observe the demonstration slides of young seeds in Lilium and/or Capsella showing developing endosperm and a young embryo.
In the remaining space, diagram and label a seed of Capsella. Be sure to use the labels printed in bold above!
The angiosperm seed is derived from the ovule which occurs within the ovary of the carpel. Changes in the ovary wall occur simultaneously with the maturation of the seed, giving rise to a FRUIT. Fruits are of various types--fleshy or dry and, when dry, dehiscent or indehiscent. In some species it may be the fruit with its contained seed(s) which is shed and distributed rather than the seed itself.
A classification of some common fruit types is given below. Use this to classify the several different fruit types available in the laboratory. Note that a number of common foods are included and that many of these are erroneously classified as "vegetables" when they are actually fruits!
Examples:
Raspberry: aggregate true drupe Apple: simple accessory pome Mulberry: multiple true drupe
Examine the peanut provided very carefully and dissect it as needed to answer the following:
Which flower parts are still visible? | stigma sepal     petal     stamen     style ovary |
How many pistils were there in the gynoecium? |   |
How many carpels were there in the gynoecium? |   |
Is the pistil simple or compound? | simple       compound |
What is the redskin? |   |
How many large fleshy structures are inside the redskin? |   |
What are these fleshy structures called? |   |
To what class of the flowering plants does the peanut belong? |   |
What is the purpose of the fleshy structures? |   |
What chemicals do they naturally contain (taste!)? |   |
Do you find a miniature plant inside these fleshy structures? | yes       no |
What part of a seed is conspicuous by its absence? |   |
Classify the peanut fruit in terms of origin: |   |
Classify the peanut fruit in terms of composition: |   |
Classify the peanut fruit in terms of description: |   |
When we eat peanuts without the redskin, do we eat a fruit, a seed, or what? |   |
When we eat peanuts with the redskin, what are we eating? |   |
Some people eat the peanuts in the "husk" or "shell" (need more fiber in your diet?)! What are these people eating? |   |
Examine the snow pea fruit very carefully and dissect it as needed to answer the following:
Which flower parts are still visible? | stigma sepal     petal     stamen     style ovary |
How many sepals were in the flower? |   |
Is the style and stigma present? | yes       no |
Was the ovary superior or inferior? | superior       inferior |
The flower was: | hypogynous   perigynous   epigynous |
The pea has a dark stripe running along one side, but lacks this stripe on the other side. Which side has the placenta? | The side with the stripe The side without the stripe |
How many locules were there in the ovary? |   |
How many pistils were there in the gynoecium? |   |
How many carpels were there in the gynoecium? |   |
Is the pistil simple or compound? | simple       compound |
How many ovules are in the locule? |   |
What color is the ovule? |   |
Do you think that the ovules have become fully mature seeds? | yes       no |
Classify the pea fruit in terms of origin: |   |
Classify the pea fruit in terms of composition: |   |
Classify the pea fruit in terms of description: |   |
Examine the cherry tomato fruit provided very carefully and dissect it as needed to answer the following:
Which flower parts are still visible? | stigma sepal     petal     stamen     style ovary |
How many sepals were in the flower? |   |
Is the style and stigma present? | yes       no |
If not, to which end of the fruit was it attached? |   |
Was the ovary superior or inferior? | superior       inferior |
The flower was: | hypogynous       perigynous       epigynous |
How many pistils were there in the gynoecium? |   |
How many locules were there in the ovary? |   |
How many carpels were there in the gynoecium? |   |
Is the pistil simple or compound? | simple       compound |
The tomato has solid walls and a solid center with seeds in between. Is the placenta attached to the walls or to the center of the fruit? | walls       center of fruit |
How many ovules are in each locule? | one       a few       many |
What color is the ovule? |   |
Classify the tomato fruit in terms of origin: |   |
Classify the tomato fruit in terms of composition: |   |
Classify the tomato fruit in terms of description: |   |
Examine the strawberry fruit provided very carefully and dissect it as needed to answer the following:
Which flower parts are still visible? | stigma sepal     petal     stamen     style ovary |
How many sepals were in the flower? |   |
How many pistils were there in the gynoecium? |   |
How many carpels were there in the gynoecium? |   |
Is the pistil simple or compound? | simple       compound |
Is the style and stigma present? | yes       no |
Was the ovary superior or inferior? | superior       inferior |
The flower was: | hypogynous       perigynous       epigynous |
From what part of the flower is all the red tissue? |   |
What color is the true strawberry fruit? |   |
Classify the strawberry fruit in terms of origin: |   |
Classify the strawberry red tissue in terms of composition: |   |
Classify the strawberry true fruit in terms of description: |   |
Go back to the Course Schedule.