Agents of Pollination:

1)      Abiotic agents:

         a)      Wind

         b)      Water

It is a chance factor for Pollen grains coming in contact with the stigma in case of both wind and water pollination. To compensate for this uncertainties and associated loss of pollen grains, the flowers produce enormous amount of pollen when compared to the number of ovules available for pollination.

2)      Biotic agents:

          a)      Insects

          b)      Birds(sunbirds and humming birds)

          c)       Bats

          d)      Reptiles

          e)      Mammals

f) Bees

g) Butterflies

h) Flies
i) Beetles

Majority of plants use biotic agents for pollination. Only a small proportion of plants use abiotic agents.

Adaptations in flowers for Pollination

I. Wind Pollination: for its success pollen grains should be light , non sticky and winged.

Anther should be  well exposed .Stigma should be  large and feathery to easily trap air-borne pollen grains.

Wind Pollinated Flowers often have one ovule in each ovary.

Example : Corn cob, Cotton, Date Palm.

 

II. Water Pollination: water is a regular mode of transport for the male gametes among the lower plant groups such as algae, bryophytes and pteridophytes.

          Example of water pollinated plants : Fresh water plants- Vallisneria, Hydrilla

                 Sea grass- Zostera  

Main features of wind and water pollinated plants.

         They produce pollen grains in large number

         They do not produce nectar

III. Insect Pollination:

       Flowers should be  large, colourful, fragrant and rich in nectar

       Pollen grains and Stigma should be sticky.

The flowers pollinated by flies and beetles secrete foul odours to attract  animals.

Certain rewards to pollinators:

Nectar and (edible) Pollen Grains are floral rewards.

 Flowers provide safe place for laying eggs .Example:- tallest flower of Amorphophallus (the flower itself is about 6 feet in height). Another example is Yucca , Moth and plant both cannot complete their life cycle without each other.

Advantages of Self Pollination:

1. It maintains the parental characters or purity of the race indefinitely.

2. Self pollination is used to maintain pure lines for hybridisation experiments.

3. The plant does not need to produce large number of pollen grains.

4. Flowers do not develop devices for attracting insect pollinators.

5. It ensures seed production. Rather it is used as fail safe device for cross-pollinated flowers.

6. Self pollination eliminates some bad recessive characters.

Disadvantages of Self Pollination:

1. New useful characters are seldom introduced.

2. Vigour and vitality of the race decreases with prolonged self pollination.

3. Immunity to diseases decreases.

4. Variability and hence adaptability to changed environment are reduced.