Name Flower Morphology Exercise




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Flower Morphology Exercise

You are already familiar with a number of aspects of the vegetative structure of angiosperms from your previous laboratory work. Now you will concentrate on flower structure, since these are the parts of the plant that are most closely associated with sexual reproduction, and are widely used in the classification of the angiosperms.

We know almost nothing about the origin(s) of the angiosperms. They are found in considerable numbers and great variety in fossils from the Cretaceous, and many of the families can be recognized as members of our modern ones. Because of the diversity of the Cretaceaous fossils, it has been suggested that the prior history must be fairly long, but only one or two possible angiosperm remains have been found in earlier geological periods. In a slab of limestone from the Yixian Formation northeast of Beijing, China botanists discovered the earliest angiosperm fossil yet found. Archaefructus (ancient fruit) is 122 to 145 million years old and so it lived in the Jurassic. It is by far the oldest angiosperm found so far. Today over 250,000 species are recognized, and the angiosperms include the principal plants covering the land surface and provide the great majority of the plants used for a variety of economic purposes.

Flower Structure


Although in gross appearance, the flowers of the angiosperms show a tremendous diversity, the parts which make up the flower are basically the same throughout. The most widely accepted interpretation of the nature of the flower is that it is a specialized branch; a stem with leaves. The following parts are recognized:

The plant stem below the flower is called the PEDICEL. At the very tip of this is the RECEPTACLE. The receptacle is found at the base in the center of the flower. Its internodes are short and the number of leaves attached to it is usually small, so the receptacle is not usually a large or obvious part of the flower.



SEPALS make up the lower (or outermost) whorl of floral leaves. They are frequently, but not always, green and rather leaf-like in appearance, although they usually are smaller than the foliage leaves of the plant. Collectively, all sepals of a flower constitute the CALYX. The major function appears to be protection of the flower parts during early development.

PETALS are attached above (inside) the sepals on the receptacle. They are usually larger than the sepals, brightly colored, and rather leaf-like in that they are broad and rather thin organs. Collectively they constitute the COROLLA. They serve as additional protection and may also attract insects and/or facilitate the pollination of the flower when the insect reaches it. The two leaflike appendages, the sepals and petals (calyx and corolla), together make up the PERIANTH of the COMPLETE flower. They may be similar in appearance to one another. One or the other or both may be missing from an INCOMPLETE flower.

STAMENS, which are found above (inside) the corolla, are rarely leaflike in appearance. Each usually is composed of two distinct parts: an elongated narrow FILAMENT rising from the receptacle and a terminal enlarged ANTHER which contains many POLLEN GRAINS. All stamens of the flower, taken together, make up the ANDROECIUM.

One or more CARPELS, are located in the center (top) of the flower. Collectively they constitute the GYNOECIUM. Each carpel has three parts. Starting at the base these are: the OVARY, an enlarged hollow region bearing one or more OVULES; a narrower, short to long STYLE; and a terminal STIGMA of a variety of sizes and shapes. If more than one carpel occurs in a flower, all may be separate from one another, but more frequently they are joined to one another to form a compound structure. The term PISTIL is often used in conjunction with the gynoecium of a flower; this may or may not be synonymous with carpel. If carpels are independent (unattached to one another) in a flower, either a single carpel or several independent ones, each carpel can be called a pistil and the flower has one or more SIMPLE pistils. If, however, more than one carpel occurs in the flower and these are all joined to one another, the flower has a single COMPOUND pistil. The cavity in the ovary portion of carpel or pistil is called the LOCULE. There is one locule in a simple pistil and one or more in a compound pistil. The portion of the ovary to which the ovule is attached is the PLACENTA. The number of ovules varies from one to several hundred per locule, depending upon the species.

Carpels are not the only flower parts that may be joined to one another. Members of each whorl in the flower may be fused to other members of the same whorl. There may also be fusion between whorls; for example, the stamens of many flowers appear to diverge from the surface of the corolla. In an extreme case, the perianth and stamens are fused to the ovary wall and become free from it only at the top of the ovary. In flowers where the floral whorls diverge below the gynoecium, the ovary is said to be SUPERIOR and the flower HYPOGYNOUS. In contrast, when the free floral whorls arise from the top of the ovary, the ovary is called INFERIOR and the flower EPIGYNOUS. An intermediate condition can be found in which the several floral whorls are attached around the middle of the ovary; it is called PERIGYNOUS.

Flowers are PERFECT, if both stamens and carpels are present but IMPERFECT if one or the other is lacking. In the latter case, both staminate and carpellate flowers may occur on the same plant (MONOECIOUS) or may be on separate plants (DIOECIOUS). Flowers may be regular, exhibiting RADIAL symmetry, or be irregular and show BILATERAL symmetry. Note, that in a longitudinal section such as the one below, it is not possible to be sure of or label the symmetry!

Use as many of the terms in bold type in the description above as possible to label the longitudinal section below (there should be at least 24 labels!):


/24

Dissecting Alstroemeria (Peruvian Lily) flowers

Examine one of the flowers provided; draw and label the flower below to show all parts and their relation to one another. Then answer the following questions about your flower:

What is the symmetry of your flower?

Are both calyx and corolla present?

The sepals are: The petals are:

How many sepals are there? _____ Petals? _____ Stamens? _____ Pistils?_____

Where are the stamens in relation, to the sepals and petals?

One per:

Stamens relatively positioned:   interior    adjacent    exterior  

If one, the pistil is

If compound, of how many carpels is the pistil composed? ________________

I determined this by counting the number of:________________ and _______________

The ovary is:

The flower is:

How many ovules are there?

Where is/are the placenta(e) to which they are attached?

Give the complete flower formula for your flower (8 pts): _____________________________

Diagram and label your flower in the space provided below. Use as many structure name labels as possible based upon the description on pages 1 and 2 (16 labels required).



Dissecting Pelargonium (Geranium) flowers

Examine one of the flowers provided; draw and label the flower below to show all parts and their relation to one another. Then answer the following questions about the geranium. Note: one floral feature that this flower may present is a stamen that lacks an anther (not by virtue of falling off…there just never was one); this is called a staminode (or sometimes staminodium). If staminodia are present, count them as if they were a second kind of stamen (i.e.: x + y in the flower formula).

What is the symmetry of your flower?

Are both calyx and corolla present?

The sepals are: The petals are:

How many sepals are there? _____ Petals? _____ Stamens? _____ Pistils?_____

Where are the stamens in relation, to the sepals and petals?

One per:

Stamens relatively positioned:   interior    adjacent    exterior  

If one, the pistil is

If compound, of how many carpels is the pistil composed? ________________

I determined this by counting the number of ________________ .

The ovary is:

The flower is:

Give the complete flower formula for your flower (8 pts): _____________________________

Diagram and label your flower in the space provided below. Use as many structure name labels as possible based upon the description on pages 1 and 2 (16 labels required).



Dissecting Antirrhinum, Saintpaulia, or Nicotiana flowers

What is the symmetry of the snapdragon flower?

Are both calyx and corolla present?

The sepals are: The petals are:

How many sepals are there? _____ Petals? _____ Stamens? _____ Pistils?_____

If one, the pistil is

If compound, of how many carpels is the pistil composed? ________________

The ovary is:

The flower is:

How many ovules are there?

Where is/are the placenta(e) to which they are attached?

Give the complete flower formula for your flower (8 pts): _____________________________



Dissecting Abutilon, Phaseolus, Euphorbia flowers

What is the symmetry of the Abutilon flower?

Are both calyx and corolla present?

The sepals are: The petals are: The stamens are:

How many sepals are there? _____ Petals? _____ Stamens? _____ Pistils?_____

If one, the pistil is

If compound, of how many carpels is the pistil composed? ________________

The ovary is:

The flower is:

How many ovules are there?

Where is/are the placenta(e) to which they are attached?

Give the complete flower formula for your flower (8 pts): _____________________________


Dissecting Begonia flowers

Examine the flowers provided; draw and label the flowers below to show all parts and their relation to one another. Then answer the following questions about begonia flowers. Note: begonia flowers introduce a new concept: the bract. This is a leaf that is associated with the flower that is not part of the flower (neither sepal nor petal, etc.) in spite of its color! Bracts are not part of a flower formula. These flowers also show us that sometimes the perianth is incomplete; in this case the showy perianth parts could be sepals OR petals, so we use tepal as a “hedged” name. In the flower formula there is only one entry for the perianth and after the number you put a T in parentheses to indicate tepals: (T). Also do not forget that a 0 needs to go into the right place in a flower formula depicting a flower lacking any other whorl!

The tepals are: How many are in male _____ and female _____ flowers.

How many stamens are in a male flower? _____

How many pistils in the female flower?_____

The flowers are:

If present, the pistil is

If compound, of how many carpels is the pistil composed? ________________

I determined this by counting the number of:________________ and _______________

The ovary is:

The flower is:

Give the complete flower formulae for your begonia flowers (16 pts):

Male:_________________ and Female:_________________

Diagram and label your flowers in the space provided below. Name the major parts visible in the flowers (ovary, style/stigma, stamen, tepal, pedicel, and any bract…8 points)


Male Flower Female Flower

stamen style/stigma

tepal tepal

pedicel ovary

bract


pedicel

Document © Ross E. Koning 1994. Permission granted for non-commercial instruction.

Koning, Ross E. 1994. Flower Morphology. Plant Information Website. http://plantphys.info/plant_biology/labdoc/flower2009.doc




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