Model Answer
0 min readIntroduction
The Brassicaceae, also known as the mustard family, is a large and economically important family of flowering plants. It comprises approximately 338 genera and around 4060 species, widely distributed throughout the world, particularly in temperate regions. These plants are characterized by their pungent glucosinolates, which produce characteristic flavors and aromas. The family includes many important agricultural crops and ornamental plants, contributing significantly to human food and economy. Understanding the characteristic features of this family is crucial for plant identification, classification, and breeding programs.
Characteristic Features of Brassicaceae
The Brassicaceae family exhibits a distinct set of characteristics that differentiate it from other plant families. These can be categorized into vegetative, floral, and fruit/seed features.
Vegetative Features
- Root System: Typically a taproot system, often well-developed and serving as a storage organ (e.g., radish, turnip).
- Stem: Herbaceous, erect, and often branched. May be cylindrical or slightly flattened.
- Leaves: Simple, alternate, and often covered with trichomes (hairs). Leaves are typically basal (forming a rosette) or cauline (arranged along the stem). Venation is reticulate (net-like).
Floral Features
- Inflorescence: Typically a raceme, which is an elongated, unbranched inflorescence with flowers borne on pedicels along a central stalk.
- Flowers: Actinomorphic (radially symmetrical), bisexual, and tetramerous (having four parts in each whorl).
- Calyx: Consists of four sepals arranged in two whorls of two each.
- Corolla: Consists of four petals arranged in the form of a cross (cruciform), hence the name ‘Cruciferae’ (older name for the family). Petals are often yellow or white.
- Androecium: Comprises six stamens, arranged in two whorls of three each. The inner stamens are shorter than the outer stamens.
- Gynoecium: Consists of a superior ovary with two carpels, forming a silique or silicle fruit.
Fruit and Seed Features
- Fruit: The characteristic fruit is a silique or silicle. A silique is a long, narrow pod with a central partition formed by the replum, while a silicle is a shorter, broader pod.
- Seeds: Small, oily seeds, often arranged in a single row within the fruit. Seeds contain abundant endosperm.
Five Species of Brassicaceae and their Economic Importance
| Species Name | Common Name | Economic Importance |
|---|---|---|
| Brassica napus | Rapeseed/Canola | Source of edible oil (canola oil), used in biodiesel production, and as animal feed. |
| Brassica rapa | Turnip/Rapini | Root vegetable consumed as food; leaves (rapini) are also eaten as a vegetable. |
| Brassica oleracea | Cabbage/Broccoli/Cauliflower/Kale | Highly variable species with numerous cultivars used as vegetables worldwide. |
| Sinapis alba | White Mustard | Seeds used for mustard condiment, oil production, and as a green manure crop. |
| Arabidopsis thaliana | Thale Cress | Model organism in plant biology research, extensively used for studying plant genetics, development, and physiology. |
Conclusion
The Brassicaceae family is a remarkably diverse and economically significant group of plants. Its distinctive floral morphology, particularly the cruciform arrangement of petals, and the characteristic silique fruit, are key identifying features. The family’s contribution to agriculture, providing essential food crops and oilseeds, underscores its importance in global food security. Continued research, particularly utilizing model organisms like <em>Arabidopsis thaliana</em>, will further enhance our understanding of plant biology and improve crop breeding strategies.
Answer Length
This is a comprehensive model answer for learning purposes and may exceed the word limit. In the exam, always adhere to the prescribed word count.