Pollination Biology in Plants

By : Ramandeep Kaur

Asst. Prof in Botany

• Pollination is the process by which pollen is transferred in the reproduction of plants, thereby enabling fertilisation and the production of fruit and seeds (sexual reproduction).
• Abiotic pollination: pollination without the involvement of other living organisms (e.g. wind or water). Only 10% of flowering plants are pollinated without animal assistance.
• Biotic pollination: pollination by a pollinator (insects are the most important pollinating animals, but birds, bats and rodents are also pollinators of some plants).

SELF- & CROSS-POLLINATION

• CROSS-POLLINATION: the transfer of pollen from an anther of the flower of one plant to a stigma of the flower of another plant.
• SELF-POLLINATION: fertilisation by transfer of pollen from the anthers of a flower to the stigma of the same flower (autogamy) or to the stigma of n another flower on the same plant (geitonogamy)

Self: no exchange of genetic material

Cross: exchange of genetic material

Hydrophilly:Pollination by water

AGENTS OF POLLINATION

Cross-pollination depends on insects visiting flowers of the same species in sequence. To help ensure that this happens, the plants have various characteristics that help pollinators locate the right flowers, including the colour, size, shape and scent of the flowers, as well as the food reward.

Sunbird: tubular, colourful flowers

Beetles: flat or cup-shaped (big) flowers

Honeybee: many varied flower types

PARTS OF THE FLOWER

ECOLOGICAL VALUE OF POLLINATION

• Valuable in their own right
• Part of ecology

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HUMAN VALUE OF POLLINATION

• Crops for human food + animal fodder
• Fibres, wood and other materials
• Plant breeding & flowers
• Medicines
• Aesthetic value

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POLLINATORS AND OUR FOOD

Insect pollination is essential for 35% of global food production. “You can thank an insect pollinator for 1 out of every 3 bites of food you eat!”

Insects pollinate the flowers of the fruit and vegetable plants we rely on for a healthy and balanced diet… (apples, melons, pumpkin, avo’s, etc)

…while most of the staple food plants can self-pollinate or are wind-pollinated (like maize and wheat), or reproduce vegetatively (like potatoes).

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A world without insect pollinators would mean a world of far fewer food choices, more expensive food, and vastly different agriculture.

HONEYBEES

Many commercial pollinator-dependent crops are reliant on the honeybee as their pollinator.

For most South African crops, honeybees are the most economically valuable pollinators because they are:

• Very effective pollinators.
• Indigenous (i.e. they are naturally found here).
• They can be managed in the huge numbers needed to supply the pollination service to our large-scale commercial crops.

Beekeepers supply the pollination service to growers/farmers, as well as harvest the honey from the bees to bottle and sell.

KNOW YOUR VEG POLLINATION!

Pollination requirements of vegetables can be discussed according to what part of the plant is eaten:

• If the ‘vegetable’ is a ‘fruit’ then pollination is required both for the production of the vegetable AND for seed production; e.g. tomatoes, peppers, eggplant, peas, beans, pumpkins, marrows, butternut, cucumbers, etc.

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• If the ‘vegetable’ is in the form of leaves or shoots (e.g. lettuce, cabbage, kohlrabi, broccoli, Brussels sprouts, spinach, Swiss Chard, leeks, onions, etc.) or is a ‘storage root’ (e.g. carrots, beetroot, turnip, parsnip, etc.) then pollination is not required or desired for the production of the vegetable, but ONLY for seed production.

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• If the ‘vegetable’ is a ‘storage stem’ then pollination is not required for EITHER the production of the vegetable or seed because seed is not required for propagation; e.g. potatoes, Jerusalem artichokes.

THREATS TO HONEYBEES & WHAT WE CAN DO�(DRAFT SLIDES FOR EDUCATORS TO EDIT AS NEEDED)

• Materials produced for the Global Pollination Project & Honeybee Forage Project South Africa, implemented by the South African National Biodiversity Institute.

Varroa mite on honeybee larva

American Foulbrood

Chemical misuse