Model Answer
0 min readIntroduction
Plant taxonomy, the science of naming, describing and classifying plants, relies heavily on floral morphology as a crucial diagnostic feature. The families Solanaceae (nightshade family) and Malvaceae (mallow family) are both economically significant and exhibit diverse floral adaptations. Solanaceae includes important food crops like tomato, potato, and brinjal, while Malvaceae encompasses cotton, okra, and hibiscus. A comparative study of their floral characteristics provides valuable insights into their evolutionary relationships and taxonomic placement. This answer will detail and contrast the floral features of these two families.
Comparative Floral Morphology of Solanaceae and Malvaceae
Both Solanaceae and Malvaceae are dicotyledonous families, but they exhibit distinct floral characteristics. The following table summarizes the key differences:
| Character | Solanaceae | Malvaceae |
|---|---|---|
| Inflorescence | Cyme (usually terminal), sometimes solitary flower | Cyme, panicle, or solitary flower |
| Flower Symmetry | Actinomorphic (radially symmetrical) | Actinomorphic (radially symmetrical) |
| Calyx | Sepals 5, united (gamosepalous), persistent | Sepals 5 (or rarely 3-7), often united, sometimes valvate, often falls off early |
| Corolla | Petals 5, united (gamopetalous), funnel-shaped or star-shaped | Petals 5 (or rarely more), united, often showy, sometimes fringed |
| Androecium | Stamens 5, epipetalous (attached to petals), filaments often unequal | Stamens numerous (often many), monadelphous (stamens fused into a single bundle), filaments often unequal, anthers often versatile |
| Gynoecium | Carpels 2, united (syncarpous), ovary superior, bilocular with many ovules in each locule, axile placentation | Carpels numerous, united, ovary superior, multi-locular with many ovules, axile placentation |
| Fruit | Berry or capsule | Capsule or schizocarp |
| Examples | Solanum tuberosum (Potato), Solanum melongena (Brinjal), Capsicum annum (Chilli) | Gossypium (Cotton), Hibiscus rosa-sinensis (Hibiscus), Abutilon theophrasti (Indian Mallow) |
Detailed Examination of Key Floral Characters
Inflorescence and Flower Symmetry
Both families predominantly exhibit actinomorphic flowers, indicating radial symmetry. However, the inflorescence type differs. Solanaceae commonly displays cymose inflorescences, where the main axis terminates in a flower, inhibiting further growth. Malvaceae, on the other hand, can have cymose, paniculate, or solitary flowers, demonstrating greater diversity in inflorescence structure.
Calyx and Corolla
The calyx in Solanaceae is typically composed of five united sepals that persist even after flowering. The corolla is gamopetalous, forming a funnel-shaped or star-shaped structure. In Malvaceae, the calyx usually consists of five united sepals, but they often fall off early. The corolla is also gamopetalous and can be quite showy, sometimes exhibiting fringed petals, as seen in hibiscus.
Androecium – A Major Distinguishing Feature
The androecium is a key characteristic differentiating the two families. Solanaceae has five stamens that are attached to the petals (epipetalous), with filaments of varying lengths. Malvaceae, however, possesses a significantly larger number of stamens, which are fused into a single bundle (monadelphous). This monadelphous condition is a defining feature of Malvaceae and is easily observable. The anthers in Malvaceae are often versatile, meaning they can move freely, aiding in pollen dispersal.
Gynoecium and Fruit Type
Both families have syncarpous gynoecia (two or more carpels fused together) with superior ovaries and axile placentation. Solanaceae typically produces berries or capsules as fruits, while Malvaceae commonly forms capsules or schizocarps (fruits that split into separate one-seeded segments).
Conclusion
In conclusion, while both Solanaceae and Malvaceae share some common floral features like actinomorphic symmetry and superior ovaries, they differ significantly in their inflorescence type, androecium structure, and fruit type. The monadelphous stamens of Malvaceae and the epipetalous stamens of Solanaceae are particularly diagnostic characteristics. Understanding these differences is crucial for accurate plant identification and taxonomic classification. Further research utilizing molecular data continues to refine our understanding of the evolutionary relationships between these two important plant families.
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.