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Angiosperm pollination syndromes

"Primative" flowers
The magnolia family (Magnoliaceae) is considered by taxonomists to be one of the least derived angiosperm families.  The flowers are relatively simple with parts arranged in whorls and having a somewhat leaf-like appearance.  There are no specialized morphological adaptations to exploit pollinators.  Insects simply crawl around on the flowers looking for the nectar reward and become dusted by pollen if they crawl over the strap-like anthers.  Relatively unintelligent insects like beetles can potentially act as pollinators of this group.  


Magnolia grandiflora (southern magnolia) - the whorl-like arrangement of parts is apparent in this image. 

Magnolia grandiflora (southern magnolia) - closeup of anthers and stigmas

Liriodendron tulipifera (tulip-tree) - insects can walk over the anthers in this simple flower.

Wind-pollinated flowers
In general, wind-pollinated flowers are green, small, and often lack petals.  The anthers and stigmas generally hang outside the flowers to allow the wind to carry the pollen.  


Juglans nigra (black walnut) - Male flowers are arranged in 
catkins which hang down to be blown by the wind.


Juglans nigra (black walnut) - Female flowers are green, with 
no petals or sepals to attract pollinators.  The stigmas are 
relatively large to catch pollen.

Acer saccharum  (sugar maple) - The anthers as well as the
flower itself hang down where they can be blown by the wind.  
The flower has no petals.  



Acer saccharum  (sugar maple) - The flowers of A. saccharum 
as well as many other wind-pollinated trees appear in the early
spring when leaves are not yet present to interfere with pollen 
movement

The flowers of grasses are located at the top of the plant where
they are exposed to the wind.


The anthers and feathery stigmas of grasses hang out of the 
flowers where they can be blown by the wind.  Petals are 
absent.

Flowers adapted for pollination by "smart" insects
As insects, bees are relatively intelligent and are able to learn how to locate and operate particular species of flowers that are in bloom at a particular time.  They are also relatively strong and are able to push their way into complicated flowers that are not accessible to other insects.  


Paulownia tomentosa (princess-tree) - bee vision is most sensitive toward the violet end of the spectrum.  So bee-pollinated flowers tend to have blue or violet markings.  Some may even have markings that are only apparent in the UV range. 

Paulownia tomentosa (princess-tree) - bee-pollinated flowers often have a lobe that serves as a landing pad.  Anthers often are located at the top of tubular petals, dusting the back of the bee as it enters.

Catalpa speciosa (northern catalpa) - a broad "landing pad" is present.

Catalpa speciosa (northern catalpa) - lines or rows of dots ("nectar guides") point the insect toward the nectar reward

Impatiens capensis (jewelweed) - landing pads and conical flower

Impatiens capensis (jewelweed) - anthers and stigma at the top of the entrance

Floral displays
Plants employ a number of methods to make their flowers more noticeable to pollinators.  All members of the large and successful Asteraceae (sunflower) family have composite inflorescences containing many flowers arranged to draw attention to the display.  

Hydrangea arborescens (wild hydrangea) - sterile flowers with large petals are arranged around the fertile flowers in the Hydrangea infrorescence

Cornus florida (flowering dogwood) - The "petals" of the dogwood inflorescence are not actually a part of the flower.  They are showy bracts (modified leaves).  The actual flowers are the small and yellow structures in the center of the display.  

Leucanthemum vulgare (oxeye daisy) - The "petals" of members of the Asteraceae family are actually "ray flowers", modified flowers that are large and bent back to draw attention to the center of the flower.  The "disk flowers" in the center are fertile.  

Echinacea purpurea (eastern purple coneflower) - another member of the Asteraceae family with disc and ray flowers.  As insects crawl over the disk searching for the reward, they move pollen between flowers.  

 

Carion flowers
Some flowers produce a bad smell and have a purplish color to simulate the rotting flesh of dead amimals.  These flowers attract beetles and carrion flies who pollinate the plant as they are fooled into trying to lay eggs on the flower.  This group includes the Araceae family, which produces highly modified flowers.  


Dracunculus vulgaris  - The "flower" consists of a purple leafy bract ("spathe") that wraps around the inflorescence.   

Arisaema triphyllum (l)   - The actual flowers in the Araceae family are tiny and located on the cylindrical "spadix" inside the spathe.  Dracunculus vulgaris (r)  - Carrion beetles are attracted to the rotten smell.  [These particular beetles (Nitidulidae) are actually feeding on pollen.]

Dracunculus vulgaris  - The stem has the mottled appearance of rotting flesh.

Dracunculus vulgaris  - The fruit develops from the flowers at the base of the spadix.  Eventually, the spathe and top of the spadix fall off.

Stapelia gigantea (carrion flower) looks like a cactus, but is actually in the milkweed family (Asclepiadaceae).

Stapelia gigantea - The flower's carrion smell attracts flies which may lay eggs on the flower.  Sometimes fly larvae that have hatched from the eggs can be seen on the flower.

Asimina triloba (paw-paw) is a small tree found in the eastern United States

Asimina triloba - Its malodorous flowers attract carrion insects.
Asimina triloba - Front view of flower. Asimina triloba - Although paw-paws commonly flower, fruit set is relatively rare.  However, commercial growers increase fruit set by hanging dead fish or road kill in the trees to attract carrion flies.

 

Hummingbird-pollinated flowers
Many hummingbird pollinated flowers are red, a color to which bird eyes are sensitive, but which is not as apparent to insects.  The hummingbird must hover and reach deep inside the flower to reach the reward.  Different species of flower may dust the bird at different locations on its body so that its pollen will be more likely to end up on another species of the same kind.  These flowers usually do not have a strong odor because the hummingbirds do not have a particularly well-developed sense of smell.


Erythrina crista-galli (crybabytree) - The 
anthers are positioned to dust the top of 
the hummingbird as it drinks.

Monarda didyma (scarlet beebalm) - No 
landing platform is necessary for a
hummingbird which can hover while drinking.

 

Moth-pollinated flowers
Moth-pollinated flowers are usually white and have a strong scent.  These features allow moths that are active at night to find the flowers.


Yucca flaccida (Adam's needle) - 
The white color is typical of moth-pollinated flowers.  Since they are
pollinated at night, attractive colors would provide little benefit.
 

Yucca flaccida (Adam's needle) - Each species of yucca
is apparently pollinated by a single, highly specialized species
of moth.  The moth has special appendages that it uses to
actively pack pollen onto the stigma.  It then oviposits its eggs
directly into the ovary.  The developing larvae eat part of the developing seeds, but this cost is outweighed by the benefit of having an efficient and reliable pollinator.  If a moth oviposits
too many eggs on a flower, the flower will abort and drop off the plant, selecting against individuals that overexploit the plant.  The yucca-yucca moth system is one of the clearest examples of coevolution between plants and animals.
 

Images copyright 2002 Steve Baskauf - Terms of use