Quick Summary
Taxonomy and Systematic Botany describes the history of plant classification and covers three important plant families in depth: Solanaceae, Fabaceae, and Liliaceae. For board exams, the floral formula, floral diagram, economic importance, and examples of each family must be memorised.
Classification Systems
| System | Basis | Proponent | Type |
|---|---|---|---|
| Artificial | One or few morphological characters | Linnaeus (stamens) | Artificial |
| Natural | Overall morphological similarity | Bentham & Hooker | Natural |
| Phylogenetic | Evolutionary relationships | Engler & Prantl | Phylogenetic |
Bentham & Hooker (1862–1883): "Genera Plantarum" — classified flowering plants into 202 orders, 3 classes (Dicots, Monocots, Gymnosperms). Still used in Indian herbaria.
Family 1 — Solanaceae (Potato / Nightshade Family)
Diagnostic features:
- Habitat: herbs, shrubs, rarely trees
- Leaves: alternate, exstipulate
- Flowers: bisexual, actinomorphic, pentamerous
- Calyx: 5 sepals, gamosepalous, persistent
- Corolla: 5 petals, gamopetalous, twisted aestivation
- Androecium: 5 stamens, epipetalous
- Gynoecium: bicarpellary, syncarpous, superior ovary, axile placentation
- Fruit: berry (tomato) or capsule (Datura)
Floral formula: ⊕ Br K(5) C(5) A5 G(2)
Economic importance:
- Food: tomato, potato, brinjal, chilli
- Medicine: Datura (atropine), Atropa belladonna
- Ornamental: Petunia
- Narcotic: Nicotiana (tobacco)
Examples: Solanum lycopersicum (tomato), Solanum tuberosum (potato), Solanum melongena (brinjal), Datura stramonium, Nicotiana tabacum
Family 2 — Fabaceae / Leguminosae (Pea / Bean Family)
Diagnostic features:
- Leaves: alternate, pinnate compound, stipulate, pulvinus at base
- Flowers: bisexual, zygomorphic, papilionaceous
- Calyx: 5 sepals, gamosepalous
- Corolla: 5 petals, vexillary aestivation (1 large standard, 2 wings, 2 keel petals)
- Androecium: 10 stamens, diadelphous (9+1)
- Gynoecium: monocarpellary, superior ovary, marginal placentation
- Fruit: legume (pod)
- Root nodules with Rhizobium for nitrogen fixation
Floral formula: % Br K(5) C1+2+(2) A(9)+1 G1
Economic importance:
- Food: pea, bean, lentil, soybean, groundnut
- Nitrogen fixation: improves soil fertility
- Timber: Dalbergia (rosewood), Tectona
- Dye: Indigo (Indigofera)
- Medicine: Glycyrrhiza (liquorice)
Examples: Pisum sativum (pea), Phaseolus vulgaris (bean), Arachis hypogaea (groundnut), Tamarindus indica (tamarind)
Family 3 — Liliaceae (Lily Family)
Diagnostic features:
- Habitat: mostly herbs with underground bulbs or corms
- Leaves: simple, alternate, parallel venation
- Flowers: bisexual, actinomorphic, trimerous
- Perianth: 6 tepals in 2 whorls of 3 each (petaloid)
- Androecium: 6 stamens in 2 whorls
- Gynoecium: tricarpellary, syncarpous, superior ovary, axile placentation
- Fruit: capsule or berry
Floral formula: ⊕ Br P(3+3) A3+3 G(3)
Economic importance:
- Food: Allium cepa (onion), Allium sativum (garlic), Asparagus
- Medicine: Aloe vera (skin care, laxative), Colchicum (gout — colchicine)
- Ornamental: Tulipa (tulip), Lilium (lily), Gloriosa
Examples: Allium cepa (onion), Allium sativum (garlic), Aloe vera, Asparagus officinalis, Gloriosa superba (flame lily — Tamil Nadu state flower)
Comparison of Three Families
| Character | Solanaceae | Fabaceae | Liliaceae |
|---|---|---|---|
| Symmetry | Actinomorphic | Zygomorphic | Actinomorphic |
| Aestivation | Twisted | Vexillary | Valvate |
| Stamens | 5, epipetalous | 10, diadelphous | 6 |
| Gynoecium | Bicarpellary | Monocarpellary | Tricarpellary |
| Placentation | Axile | Marginal | Axile |
| Fruit | Berry/Capsule | Legume | Capsule/Berry |
Important Questions
One Mark
- Name the type of aestivation in Fabaceae.
- What is diadelphous condition in stamens? Give one example.
- Name the state flower of Tamil Nadu and its family.
- What is the placentation in Solanaceae?
Short Answer (3 marks)
- Write the floral formula and two economic uses of Fabaceae.
- Describe the androecium and gynoecium of Liliaceae.
- Distinguish between natural and phylogenetic classification systems.
Long Answer (5 marks)
- Describe the salient features of Solanaceae with floral formula, floral diagram, and economic importance.
- Compare Solanaceae, Fabaceae, and Liliaceae on the basis of symmetry, aestivation, stamens, gynoecium, placentation, and fruit.
Common Mistakes
- Diadelphous: 9+1 in Fabaceae — NOT all 10 fused; one stamen is free.
- Liliaceae perianth: NOT sepals and petals — they are tepals (perianth segments, all petaloid).
- Solanaceae fruit: tomato is a berry, NOT drupe (endocarp is not hard).
- Fabaceae is zygomorphic; Solanaceae and Liliaceae are actinomorphic — don't mix them.
Board Exam Tips
- Each family's floral formula + diagram + 3 examples + 3 economic uses is a guaranteed 5-mark question.
- The comparison table of 3 families is another standard 5-mark question.
- Gloriosa superba (Tamil Nadu state flower) belongs to Liliaceae — this appears as a 1-mark question.
- NEET: Family identification from features and economic importance questions appear regularly.