What is a Stamen?
The stamen is the male part of a flower that makes pollen. Each stamen has two parts: a slender stalk (filament) and a pollen-producing tip (anther). Together, all the stamens in a flower are called the androecium.
Structure
Two Main Parts
Filament:
- Thread-like stalk
- Supports and positions anther
- May be short or very long
- Can be fused or free
Anther:
- Usually two lobes
- Contains pollen sacs (microsporangia)
- Produces and releases pollen
- Opens by splits or pores
Number and Arrangement
Variation
Few stamens (1-5):
- Some orchids have one
- Many flowers have 5
- Efficient pollen production
Many stamens (dozens to hundreds):
- Ceiba has 100+ stamens
- Creates showy flower
- Backup for pollination
Patterns
Free stamens: Each separate Fused stamens: United in groups Monadelphous: All stamens fused in one group Diadelphous: Stamens in two groups
Pollen Production
Process
- Microsporogenesis: Cells divide in anther
- Pollen grain formation: Each grain contains male gametes
- Anther maturation: Pollen ripens
- Dehiscence: Anther splits open
- Release: Pollen dispersed by wind, insects, birds
Pollen Types
Wind-dispersed (anemophilous):
- Small, light, smooth
- Produced in huge quantities
- Major allergen source
Animal-dispersed (zoophilous):
- Larger, sticky, sculptured
- Less produced
- Attached to pollinators
Costa Rican Examples
Guanacaste (Enterolobium cyclocarpum)
- Many long stamens
- White, fluffy flower balls
- Stamens give spherical appearance
- Bee-pollinated
Roble de Sabana (Tabebuia rosea)
- 4 stamens (typical for family)
- Two pairs of unequal length
- Hidden inside pink trumpet
- Bee-pollinated
Cortez Negro (Handroanthus chrysanthus)
- 4 stamens
- Yellow anthers visible
- Inside purple-pink flower
- Large nectar reward for bees
Function in Pollination
Mechanisms
Direct contact:
- Pollinator brushes against anther
- Pollen sticks to body
- Transferred to pistil of next flower
Explosive release:
- Some stamens spring when touched
- Dust pollinator with pollen
- Trigger mechanisms
Gradual release:
- Anthers open slowly
- Pollen available over days
- Multiple pollinator visits
Modified Stamens
Staminodes
Non-functional stamens:
- Lost pollen production
- May be showy (petal-like)
- Can produce nectar
- Part of flower symmetry
Example: Some orchids have showy staminodes
Timing
Protandry
Stamens mature first:
- Pollen released before pistil receptive
- Prevents self-pollination
- Promotes outcrossing
Protogyny
Pistil matures first:
- Receives pollen from other flowers
- Then stamens release pollen
- Also prevents self-pollination
Identification Value
Family Characteristics
Fabaceae (legumes):
- Usually 10 stamens
- Often fused at base
- Diagnostic feature
Malvaceae (hibiscus family):
- Many stamens
- Fused in column around pistil
- Very distinctive
Bignoniaceae (trumpet trees):
- Usually 4 stamens
- Hidden in tube
- One or two may be sterile
Economic Importance
Food Products
Saffron (spice):
- Actually dried stigmas (female part)
- But harvested from crocus flowers
- World's most expensive spice
Pollen supplements:
- Bee pollen collected
- Nutritional supplement
- From stamens of many flowers
Allergens
Hay fever:
- Wind-pollinated tree pollen
- Major allergen source
- Peak seasons (dry-rainy transition)
Costa Rican allergenic trees:
- Cypresses
- Some palms
- Wind-pollinated species
Why It Matters
Understanding stamens helps with:
- Flower identification: Number and arrangement diagnostic
- Pollination: Understanding reproduction
- Breeding: Controlled pollination for hybrids
- Allergies: Identifying pollen sources
- Conservation: Protecting pollinators
Field Tips
Examining stamens:
- Count them (diagnostic!)
- Note if free or fused
- Check anther color
- Look for pollen
- Measure length relative to pistil
Best time to observe:
- Early morning (fresh pollen)
- Peak flowering season
- Flowers just opening