Problem 122 - Objective Biology for NEET

Question

The floral formula of Brassicaceae is (a) \(\oplus \delta \mathrm{K}_{2-2} \mathrm{C}_{4} \mathrm{~A}_{2+4} \underline{\mathrm{G}}_{(2)}\) (b) \(\oplus \sigma^{*} \mathrm{~K}_{2+2} \mathrm{C}_{4} \mathrm{~A}_{2+4} \underline{\mathrm{G}}_{(2)}\) (c) \(\oplus \oint \mathrm{K}_{2+(2)} \mathrm{C}_{4} \mathrm{~A}_{2-4} \underline{\mathrm{G}}_{(2)}\) (d) \(\oplus \delta \mathrm{K}_{2+2} \mathrm{C}_{(4)} \mathrm{A}_{2+4} \underline{\mathrm{G}}_{2}\)

Step-by-Step Solution

Answer

(d) \(\oplus \delta \mathrm{K}_{2+2} \mathrm{C}_{(4)} \mathrm{A}_{2+4} \underline{\mathrm{G}}_{2}\) is the correct floral formula for Brassicaceae.

Step 1 - Understanding the given options

The floral formula given in each option represents different flower structures. Analyze each formula to see how closely they match with the typical characteristics of the Brassicaceae family.

Step 2 - Analyzing option (a)

Option (a) represents a flower with radial symmetry (\(\oplus\)), with the calyx (\(\mathrm{K}_{2-2}\)), corolla (\(\mathrm{C}_{4}\)), androecium (\(\mathrm{A}_{2+4}\)), and gynoecium (\(\underline{\mathrm{G}}_{(2)}\)). However, it is not the correct formula for the Brassicaceae family as the floral parts are not correctly represented.

Step 3 - Analyzing option (b)

Option (b) corresponds to a flower with bilateral symmetry (\(\sigma^*\)), which is incorrect for the Brassicaceae family. Radial symmetry is more typical of this family.

Step 4 - Analyzing option (c)

Option (c) represents an irregular symmetry (\(\oint\)), which is also incorrect for the Brassicaceae family.

Step 5 - Analyzing option (d)

Option (d) corresponds to a flower with radial symmetry (\(\oplus\)), with the calyx (\(\mathrm{K}_{2+2}\)), corolla (\(\mathrm{C}_{(4)}\)), androecium (\(\mathrm{A}_{2+4}\)), and gynoecium (\(\underline{\mathrm{G}}_{2}\)). It includes four united petals (\(\mathrm{C}_{(4)}\)), which is a characteristic feature of the Brassicaceae family.

Step 6 - Finding the correct option

Analyzing each of the options leads to the conclusion that Option (d) is the correct floral formula for the Brassicaceae family.

Key Concepts

Plant Morphology

Plant morphology is the study of the physical form and external structure of plants. In botany, understanding the morphology of plants is crucial as it helps in identifying and classifying different species. For students and botanists, the morphology of flowers can be particularly interesting, as flowers contain specific structures that play significant roles in the reproduction of the plant.

In the study of plant morphology, the examination of the number, shape, size, and arrangement of the various parts of a flower is key. In the case of the Brassicaceae family, flowers have distinct structural features. They typically have four petals arranged in a cross, which is why they are often referred to as crucifers. Additionally, they have six stamens, with four being longer than the others, and their ovaries contain two carpels.

By paying close attention to these morphological traits, students can more readily identify members of the Brassicaceae family, and understand the functional significance of each floral part in the plant's life cycle.

Botanical Nomenclature

Botanical nomenclature is a system of naming plants scientifically. This system helps in providing a universal language for botanists and serves as a means of classifying and identifying plants without confusion. The rules for naming plants are set out by the International Code of Nomenclature for algae, fungi, and plants (ICN).

The importance of botanical nomenclature becomes evident when studying plant families like Brassicaceae. Understanding the standard format and symbols used in a floral formula is essential for correctly communicating the structure of a flower. For example, in the floral formula \( \oplus \delta \mathrm{K}_{2+2} \mathrm{C}_{(4)} \mathrm{A}_{2+4} \underline{\mathrm{G}}_{2} \) for Brassicaceae, each symbol indicates a different aspect of the flower's structure, allowing for detailed analysis without the need for long descriptions.

Students should familiarize themselves with the key codes and symbols such as \( \oplus \) for radial symmetry, \( \delta \) for a bisymmetrical flower, and \( \underline{\mathrm{G}} \) to indicate a fused carpel or gynoecium. By mastering these symbols, students can quickly read and write the floral formula of any plant.

Flower Structure Analysis

Flower structure analysis involves the careful examination of a flower's parts to understand its reproductive strategy and classify it within a plant family. Each component of the flower, from petals and sepals to stamens and pistils, has a specific role and arrangement.

The floral formula is a compact expression used to symbolize the number and arrangement of floral parts. It is a critical tool in flower structure analysis because it conveys a lot of information in a brief but precise way. For instance, when analyzing the provided options for the Brassicaceae family, recognition of the correct symmetry, number of petals, stamens, and carpels was crucial in identifying the right floral formula.

For Brassicaceae, radial symmetry is represented by \( \oplus \) and is a defining characteristic of the family. The wrong symmetry, such as bilateral \( \sigma^* \) or irregular \( \oint \) in options (b) and (c) respectively, quickly eliminates those answers. Option (d) provides us with a match to the known morphology of Brassicaceae flowers, with four united petals (\( \mathrm{C}_{(4)} \) and six stamens (\( \mathrm{A}_{2+4} \) indicating two outer and four inner, a unique feature of this family). This synthesis of floral morphology and correct nomenclature ultimately guides you to the solution.