Introduction

The main reproductive organ of angiosperms is the flower. Our goal throughout this experiment is to analyze the structure of this organ and, based on the observations made, to establish the floral formula of the given specimen. This specific paper will use the apple blossom (Malus domestica) as an example.

Theoretical Analysis

A hermaphrodite flower, such as the apple blossom, contains both male and female reproductive organs, as well as protective structures:

• Starting from the stem, we can observe the floral pedicel, the receptacle (fun fact: apples are considered a false fruit because they are the result of the development of the said receptacle), the calyx, and the corolla that protect the inner reproductive structures, the androecium and the gynoecium.
• The calyx is formed by sepals, small green structures present under the petals of dicotyledon flowers.
• The floral corolla is formed by petals whose disposition determines the type of symmetry of the flower. Both sepals and petals can be either separate or united.
• The male component, or the androecium, contains the stamens, reproductive units that are formed by a pollen-rich top structure called the anther that is supported by a filament.
• - From top to bottom, the gynoecium, or the pistil, is divided into three main parts: the stigma, which is the site of arrival for pollen particles; the style, through which the pollen tubes develop, reaching down into the ovary; and the ovary. The ovary contains female reproductive units, called carpels, containing ovules. If the gynoecium is visible from the exterior, the flower is called epigynous; if not, it is considered hypogynous.

Apple anatomy, flower and fruit compared, Chiswick Chap, CC BY-SA 4.0

Necessary Tools and Materials

• Fresh apple blossoms
• Tweezers
• Scalpel
• Dissecting tray

Experimental Method

The two main objectives to have in mind during this experiment are the attentive observation of the floral components and the identification of the correct floral formula. The following steps attempt to achieve both goals simultaneously.

1. Establish the sex of the flower. Write down ♂ for male, ♀ for female and ⚤ for hermaphrodite.
2. Establish the symmetry of the flower. Write down ̶X̶ for radial symmetry (actinomorphic flower) or ↑↓ to represent bilateral symmetry.
3. Count the number of sepals in the calyx. Write down K followed by the number in subscript. If the elements are grown together, put the number between parentheses. If, at any point, the number of elements in a cycle cannot be properly determined, write down the infinity symbol in subscript.
4. Count the number of petals in the corolla. Write down C followed by the appropriate index in subscript.
5. Count the number of stamens in the androecium by cycle, from the outside in. Write down A followed by the number of stamens in each cycle with the + symbol in between, in subscript.
6. Establish if the flower is epigynous or hypogynous. If the gynoecium is inferiorly placed, write down an overlined G, otherwise use G as a symbol for superior pistil placement.
7. Gently remove the petals and isolate the stamens using the tweezers. After identifying the pistil, carefully cross section the ovary with the scalpel and count the number of carpels found inside. Write down the appropriate index after the symbol used for the gynoecium (G). If the carpels are grown together, do not forget to put the number in between brackets.

Expected Results and Conclusion

The apple blossom is epigynous, actinomorphic, and hermaphroditic, and its elements form 6 concentric cycles, as described by the following floral formula:

⚤ X̶ \(\text{K}_5 \; \text{C}_5 \; \text{A}_{10+5+5}\) G\( _5\)

Necessary Skills and Troubleshooting

In order to obtain a successful analysis of the reproductive parts of a plant, accurate counting skills are needed, as well as precision when using the scalpel and tweezers to section and remove components during the dissection process. Errors may appear due to destruction of the biological material, caused by inattentive manipulation of fine or fragile components.

Malus domestica flower and buds