Experiment 6: Study of Adaptations of Flowers Pollinated by Different Agencies (WIND, INSECT, AND BIRD)

AIM

To study adaptations of flowers pollinated by different agencies (wind, insect, and bird).

PRINCIPLE

Pollination is transfer of pollen grains from anther to stigma. Different agencies like wind, water, insects and birds carry pollen. Flowers show specific adaptations to facilitate pollination by their particular agency.

Anemophilous flowers are small, inconspicuous and produce large amount of light, dusty pollen. Entomophilous flowers are bright, showy and produce nectar to attract insects. Ornithophilous flowers are large, tubular and produce abundant nectar.

Study of floral morphology, pollen characteristics and stigma structure helps to identify adaptation to different pollinating agents. These adaptations ensure successful cross pollination and increase efficiency of reproduction.

REQUIREMENTS

• Compound microscope
• Hand lens
• Forceps
• Needle
• Slides
• Cover slip
• Fresh flowers of maize or grass
• Salvia
• Bignonia
• Vallisneria, etc.

PROCEDURE

1. Select at least one flower for each category (wind, insect, water and bird).
2. Observe its morphological characteristics. Note down the adaptations of the flower in its structure to facilitate pollination by external agencies.
3. Dissect it out to see its male and female reproductive parts.
4. Dust the pollens on a drop of water on slide.
5. Now, observe the characteristics of pollens under microscope.
6. And draw a labelled diagram of each category.

OBSERVATION

Flowers pollinated by different agencies show distinct structural adaptations in size, colour, odour, nectar production, pollen type and stigma morphology to suit their specific pollinators.

1) Anemophily (Pollination by Wind)

A. Maize (Zea mays)

• Maize plant bears male and female flowers separately on the same plant. Male flowers are terminal whereas female flowers are axillary in position.
• Flowers are small, inconspicuous, colourless, odourless and nectar less.
• Both stigma and anthers hang outside the perianth (exerted in position).
• Pollens are light, small and dusty. They are produced in large numbers.
• Stigma is hairy, feathery, branched and sticky to catch wind dispersed pollens.

B. Pinus (Pine)

• The pollens are produced in huge numbers.
• They are light weighted.
• The pollen possess wings, which help them to float along with wind to far-off places.

C. Grasses (Wheat and Rice)

• Flowers are not brightly coloured or showy and are inconspicuous in nature.
• They do not bear scent and do not produce nectar, but produce light weighted pollen grains in large numbers.
• Stigma is feathery to catch pollen.

2) Entomophily (Pollination by Insect)

Salvia

• The flowers are showy, brightly coloured and attract insects like honeybees.
• They are borne on verticellaster inflorescence to become conspicuous.
• Each flower has two epipetalous stamens in which stamen is attached to the petals by filaments.
• In older flowers, the style brings the stigma in such a position that it brushes against the back of insect and collects pollen grains brought by the insect from a young flower.

3) Ornithophily (Pollination by Birds)

Bignonia

• The flowers are big and brightly coloured red, orange, yellow or blue.
• The flower parts are thick and leathery especially corolla.
• The flowers produce abundant nectar and may also have certain edible parts. Birds visit flowers for feeding on this nectar.
• The flowers are usually odourless (without any fragrance or scent).

Examples

RESULT

The different types of flowers adapt themselves according to their habitat, availability and the type of pollinators. In this way, they show great variations in their morphological features along with special adaptive features.

CONCLUSION

Adaptations for anemophily include light dusty pollens and feathery stigma, for entomophily include bright colour and nectar, and for ornithophily include large tubular red flowers with abundant nectar. These adaptations ensure efficient cross pollination.

PRECAUTIONS

• The fresh flowers should be taken to study the morphological features.
• The pollens should be gently dusted on slide with a drop of water before observing them under the microscope.