Seeds and germination The flower Pollination Fertilisation Seed dispersal Vegetative reproduction

As is the case for animals, flowering plants have systems to maximise efficiency of reproduction to ensure the species survives through time.

Seeds and germination
Seeds contain both a food source and a small embryonic plant in a dormant state. Given a supply of freshwater and sufficient warmth, the seed will germinate, with the plant root growing through the water-softened seed coat and down towards water and the pull of gravity. The shoot then grows upwards through the soil to light.

Seeds of some Australian native trees (e.g. wattles) only germinate after bushfires. This ensures they only germinate when there is less competition by other plants for space and light.

The flower
The germinated seedling continues to grow and uses up its stored food supply until it breaks through the soil surface, develops more roots and green leaves, and can photosynthesise (see Plant systems B: Photosynthesis, nutrition and respiration). It then grows, matures and develops reproductive systems called flowers.

Some species have separate male and female flowers, but most produce both pollen (male gametes or sex cells) as well as ovules (female gametes or egg cells) on the same flower.

The "male" organ is the stamen with a stalk (filament) and a large lobed tip (anther), where the pollen is produced.

The "female" organ (the pistil) includes the ovary where the ovules are formed, and the sticky stigma on top of a stalk-like style.

Pollination
As plants cannot move about to mate, they rely on other organisms, wind, or water to transport the pollen to other flowers. Cross-pollination increases biodiversity in the offspring by mixing two parental types, but some plants do self-pollinate.

Pollination

• Vector-pollinated flowers are bright coloured, curious shapes, scented, and contain nectar and plenty of pollen to attract insects and birds. These pollen carriers (vectors) inadvertently get excess pollen on them which wipes off onto the broad, grooved, sticky stigmas of other flowers they visit. Many flowers have the arrangement of floral parts to prevent self-fertilisation.
  
  
• Wind-pollinated flowers lack large, bright petals and scent, and produce abundant pollen on long dangling stamens, from flowers well above leaves (e.g. grasses) or flowers which emerge before the leaves (e.g. many deciduous trees). The stigmas are long and feathery to catch the wind-blown pollen thus increasing the chance of pollination.

Fertilisation
When the pollen grain lands on the stigma of another flower of the same species, a pollen tube grows down to fertilise the ovule, forming the embryonic seed plant. The ovary area develops into a fruit enclosing the seeds. Thus an apple with six seeds is formed from one flower which was successfully pollinated by at least six pollen grains fertilising six ovules.

Seed dispersal

Seeds must be carried to other areas to reduce competition between new seedlings for resources (light, space and water). This may be on animal feet or fur (e.g. sticky burrs), by water or wind, or via animals eating the fruits and dropping the indigestible seeds elsewhere (e.g. plum or apple) or in faeces (e.g. tomato, blackberry).

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