Agents of Pollination

Agents of pollination:

The agents responsible for pollination have been grouped into two main categories :

A. Abiotic agents

B. Biotic agents

A. Abiotic Agents: These are non-living agents which include wind and water. 

   1) Pollination by wind (Anemophily)- Most of the important crop plants are wind pollinated. These include wheat, rice, corn, rye, barley and oats. 

Adaptations in anemophilous flowers: 

• The flowers are small, inconspicuous, colorless, without nectar and fragrance (odour). 

• The pollen grains are light in weight, dry and produced in large numbers to increase chances of pollination considering wastage of pollen grains. 

• Stigma is feathery to trap pollens carried by wind currents. 

 Pollination by wind (Maize)

  2) Pollination by water (Hydrophily)- Found only in some 30 genera of aquatic monocots. E.g. Vallisneria, Zostera, Ceratophyllum etc. 

Adaptations in hydrophilous flowers  

• Flowers are small and inconspicuous. Perianth and other floral parts are unwettable. 

• Pollen grains are long and unwettable due to the presence of mucilage.  

• Nectar and fragrance are lacking in flowers. 

   Types of Hydrophily 

  1) Hypohydrophily- It is a type of underwater pollination in which pollen grains are transferred to the stigma while submerged in water. This approach is commonly found in aquatic plants such as seagrasses. 

  2)  Epihydrophily- It is a type of pollination in which pollen is transmitted to the surface of the water. This type of pollination is seen in aquatic plants like Vallisneria, where pollen floats on the water's surface and reaches female flowers. 

Male and female plants-Vallisneria

B. Biotic Agents: It includes living agents. About 80% of plants require the help of other living, moving creatures such as insects, birds, bats, snails to transfer their pollens from one flower to another.  

1) Pollination by insects (Entomophily)- It occurs in Rose, Jasmine, Cestrum, etc. 

Adaptations in entomophilous flowers  

• They are large, showy and often brightly colored.  

• The flowers produce a sweet odour (smell) and have nectar glands. 

• The stigma is rough due to presence of hair or is sticky due to mucilaginous secretion. 

Lever mechanism in Salvia

  2) Pollination by birds (Ornithophily)- Only a few types of birds are specialized for pollination. They usually have small sizes and long beaks e.g. Sun birds and hummingbirds. Some ornithophilous plants are Bombax, Callistemon (Bottle Brush), Butea, etc.

Adaptations in ornithophilous flowers 

• Flowers are usually brightly colored, large and showy.  

• They secrete profuse, dilute nectar. Pollen grains are sticky and spiny.  

• Flowers are generally without fragrance, as birds have poor sense of smell. 

Ornithophily

3) Pollination by Bats (Chiropterophily)- Bats can transport pollens over long distances, sometimes several kilometers. 

Adaptations in Chiropterophilous flowers  

• Flowers are dull colored with a strong fragrance.  

• They secrete abundant nectar.  

• Flowers produce large amounts of edible pollen grains, e.g. Anthocephalous (kadamb tree)
• , Adansonia (Baobab tree/ Gorakh chinch), Kigelia (Sausage tree).
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