BOTANY LABORATORY PRACTICAL (PLANT ANATOMY AND MORPHOLOGY) - O.A. SHEVCHUK - 2014

THE FLOWER

TOPIC 7. FLOWER FORMULA AND DIAGRAM

General notes. The characteristics of a flower can be summarized in the form of a formula, which uses specific symbols for its floral parts: simple perianth - P (Perigonium) or the Ukrainian letter О; calyx - K or Ca (Calyx) - Ч; corolla - C or Co (Corolla) - В; androecium - A or (Androeceum) - А (or Т); gynoecium - G (Gynoeceum) - Г (or М).

Ukrainian letters are typically used in secondary schools.

Flower types also have conventional symbols:

- bisexual flower (this symbol is usually omitted in formulas),

- female, pistillate flower;

- male, staminate flower;

* or - actinomorphic (regular) flower;

.|. or ↑ - zygomorphic (irregular) flower.

The number of individual flower parts is indicated by numbers (e.g., a five-petaled corolla - Co₅, a six-part androecium - A₆), and when their number is equal to or exceeds 12, the infinity symbol ∞ is used.

If sepals are fused, the number indicating their quantity is enclosed in parentheses. When separate PARTS OF THE calyx, corolla, or simple perianth are arranged in multiple whorls (circles), the numbers indicating their count in each whorl are connected by a plus sign (+), for example, the simple perianth of a lily - P₃₊₃.

The formula should reflect the number of carpels forming the gynoecium, whether they are fused into a single pistil (syncarpous) or each carpel forms a separate pistil (apocarpous gynoecium), as well as THE POSITION OF the Ovary - superior or inferior. For example, a syncarpous gynoecium with an inferior ovary in a pumpkin flower is designated in the formula as G₍₃₎, where ₍₃₎ indicates that the gynoecium consists of three fused carpels, and the bar above denotes an inferior ovary. A superior ovary is similarly designated with a bar below.

A more comprehensive understanding of floral Structure is provided by a diagram, which is a PROJECTION OF THE flower onto a plane perpendicular to its axis. The diagram shows not only the number but also the arrangement and mutual positioning of the floral parts. For convenience, a standard orientation is adopted: the inflorescence axis is at the top, and the bract is at the bottom. Floral parts are always represented by specific shapes. The inflorescence axis is denoted by a small circle, though this circle is omitted if the flower is terminal; the bract and sepals are shown as crescent-shaped arcs with a keel; petals as Heart-shaped arcs without a keel; stamens by shapes roughly reflecting the cross-sectional contours of an anther; and the gynoecium resembles the cross-section of an ovary. Inside the ovary, small circles indicate ovules on the corresponding parts of the carpels. When floral parts are fused, the shapes representing them on the diagrams are connected by lines. Like formulas, diagrams can be empirical, showing only the visible parts of the flower, or theoretical, also indicating reduced or entirely missing parts.

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Fig. 41. Flower diagram and The Relationship of its parts to the floral structures:

1 - inflorescence axis; 2 - bracts; 3 - sepal; 4 - petal; 5 - stamen; 6 - gynoecium; 7 - bracteole.

Objective: to study the principles of writing a flower formula using a set of conventional symbols; to study the principles of constructing a floral diagram.

Materials and equipment: live or preserved flowers of various plants, laboratory equipment, hand lenses, charts.

Tasks

Example of deriving a flower formula when examining a pea flower.

Fig. 42. Pea flower:

A - general view; B - flower diagram; C - STRUCTURE OF THE corolla: 1 - banner (standard), 2 - wings (alae), 3 - keel; D - androecium; E - gynoecium.

This is a typical zygomorphic flower. Using a magnifying Glass, examine the parts of the flower carefully and determine the number of sepals, petals, stamens, and pistils; how many whorls they are arranged in; and their relative positions—petals in relation to sepals, and stamens in relation to petals.

Dissect one of the flowers onto a piece of cardboard or a Microscope slide. Begin with the Analysis of the calyx. There are 5 sepals, arranged in a single whorl and fused together. In the formula, write Ca₍₅₎. There are 5 petals of different sizes: the largest petal is the standard (banner); two lateral petals, similar to each other, are the wings; and two anterior petals are fused to form the keel. In the formula, we write:

Co₍₃₊₂₎

Next, we examine the androecium; it consists of 10 stamens, of which 9 are fused. In the formula, we write:

А₁₊₍₉₎

The gynoecium consists of a single carpel, and the ovary is superior. In the formula, we write: G₁

Overall, the floral formula for the pea takes the following form:

Ca₍₅₎Co₃₊₍₂₎A₁₊₍₉₎G₁

This is the empirical formula. Taking into account the Ontogeny of the flower, the theoretical formula will be somewhat different:

Ca₍₅₎Co₃₊₍₂₎A_1+(5+4)G₁

1. Compose the formulas of the flowers provided to you. Write them down.

2. Construct a diagram of the flower provided to you. Make a drawing of it.

Draw your Conclusions.

Floral formulas:

Floral diagram

Conclusion

Self-Assessment Questions

1. Which provides a more complete understanding of flower structure—the formula or the diagram?

2. What symbols are used to denote flower parts in the formula and in the diagram?

3. How is the fusion of floral Organs represented in a formula or a diagram?

4. Which formula is called empirical and which is called theoretical?