POLLINATION (PS14) Flashcards
State the functions of meaning of ‘monoecious’ and dioecious’ in relation to plants,
2 plant examples for each needed
Dioecious plants
Produce separate male and female plants.
Self pollination is impossible in such plants - but they are very few species.
Ilex aquifolium
Skimmia japonica
MONOECIOUS PLANTS
produce several male and female flowers on the same plant. Encourages cross-pollination between adjacent species - whilst still allowing for self-pollination if plant is isolated from those of the same species.
State the meaning of pollination
Pollination is the transfer of pollen grain (which contains the male gamete) from the anther to the surface of the stigma (female). This process precedes fertilisation.
Pollination May occur within the same flower / or flowers on the same plant (self pollination) or between flowers on separate plants of the same species (cross pollination)
In most plants pollination is carried out either by insects (entomophilous pollination ) or by wind (anemophilous pollination). Less commonly, animals or water are the agents of pollination.
The flower is able to identity pollen by its shape and chemical make up and rejects pollen from unsuitable source.
Describe the characteristics of wind and bee pollinated plants -variations in flower structure and pollen.
WIND POLLINATED
- petals, sepals and nectaries May be absent, reduced or green.
- flowers have large pendulous anthers- which sway in the lightest of breezes, shaking out abundant pollen - which is small and light so can be easily carried away on the wind.
1 - male flowers produce greater amount of pollen compared to insect pollinated flower
2- pollen grains are light
3- pollen grains are small
4- often stamen hang out of the flower
5- Carpel is short - reduced style
6- stigma surface is feathery & has greater surface area
Examples include grass family (Poaceae) and many trees e.g Betula pendula (birch), Quercus robur (oak)
INSECT POLLINATED (bees, butterflies, beetles, birds, bats, lizards)
1-,have large brightly coloured petals
2- often scented and have nectaries/and is honey guides.(visible in ultra violet - guide pollinators to centre if flower)
3- pollen grains are often large, sticky and spiky (to cling to insects body)
4- produce less pollen than wind pollinated plants (generally)
5- Anthers are relatively short - placed where insects will brush against
6- stigmas are sticky or wrinkled -,places where bees can brush against
7- are commonly single flowers - often blue/purple/yellow
Examples:
Digitalis purpurea (foxglove)
Viola ‘floella’
ANIMAL POLLINATED
Birds can play important role in pollination if some plant species
Eg- hummingbirds on fuschia in California
(Pollen sticks to hairs at base of bill)
BATS - pollinates tropical species of flowers that open at night - big to allow bats head in, ie: Stenocereus thurberi (organ pipe cactus )
WATER POLLINATED
VERY few
Vallisneria spiralis (Ribbon weed) female flowers are on long stalks that bend over and touch the water surface. Make flowers are released under water - they float to surface and eventually make contact with female flowers and transfer the pollen.
Describe self pollination
1- movement of pollen from Anther to stigma in the same flower
2- movement of pollen from 1 flower to another flower on the same plant
Describe cross -pollination
This is the most favourable method of pollination for a plant. But In most cases most plants have a fail safe self pollination method
Movement / transfer of pollen grain onto the stigma of a flower on another plant of the same, or closely related species
List the effects environmental conditions can have on pollination
TEMPERATURE
Low temps = less active insects = less pollination
Frost - result in death of flowers
WATER
Effects both wind and insect pollinated flowers.
Insects - less active
Pollen becomes wet and heavy resulting in less wind blown pollen. Rain and hail can also damage flowers - less pollen produced/received
WIND
Reduce flying insect activity
High winds damage flowers -less pollen produced/received
Describe differences between PROTANDRY & PROTOGYNY
Anthers and stigmas within a single flower sometimes mature at different times, thus encouraging cross pollination.
ANTHERS MATURE FIRST - PROTANDRY
Lamium album
STIGMAS MATURE FIRST - PROTOGYNY
Hyacinthoides non-scripta (bluebell)
Usually , to ensure pollination does occur, there is an overlap period when both anthers and stigmas are ripe, allowing for self pollination if cross-pollination has not occurred.
Describe self incompatibility
Some plants are genetically determined to be self incompatible. Even if self pollination occurs, self fertilisation is often made less likely or impossible by slow or absent pollen tube growth. Trifolium repens (clover) is an extreme case of self incompatibility.
Special structures
Plants such as primula vulgaris have a morphological adaption, which favours cross pollination.
Cross pollination in primrose :
A - pin eyed (stigma high and anthers low)
B- thrum eyed (stigma low and Anthers high)
