1. Introduction
Terpenoids (also called isoprenoids) are one of the largest classes of plant secondary metabolites.
They are derived from five-carbon isoprene units and participate in diverse biological functions.
Terpenoids contribute to plant aroma, pigmentation, hormonal regulation, and defense.
2. Structural Classification
Terpenoids are classified based on the number of isoprene units:
| Class |
Carbon Units |
Examples |
Relevance |
| Monoterpenes |
C10 |
Essential oils |
Aroma in herbs and fruits |
| Sesquiterpenes |
C15 |
Defense compounds |
Pest resistance |
| Diterpenes |
C20 |
Gibberellins |
Growth regulation |
| Triterpenes |
C30 |
Plant sterols |
Membrane structure |
| Tetraterpenes |
C40 |
Carotenoids |
Fruit color |
3. Biological Functions
- Attraction of pollinators through volatile compounds
- Defense against herbivores and pathogens
- Regulation of plant growth (gibberellins)
- Photoprotection (carotenoids)
- Membrane stability (sterols)
Terpenoids integrate ecological interaction with biochemical regulation.
4. Applied Interpretation in Horticulture
- Fruit aroma depends largely on volatile terpenoids.
- Carotenoids determine yellow and orange pigmentation.
- Growth regulators used in horticulture are terpenoid-derived.
- Essential oil crops depend on monoterpene accumulation.
Examples include aromatic herbs, citrus fruits, and carotenoid-rich vegetables.
5. Integration with Crop Quality and Market Value
- Flavor intensity is linked to terpenoid composition.
- Color uniformity affects consumer preference.
- Natural plant defenses reduce pesticide dependency.
- Medicinal and industrial applications enhance economic value.
Terpenoid metabolism connects plant ecology, physiology, and commercial horticulture.