Reproduction In Plants

Reproduction

Process of making more of the same kind of organism

Asexual reproduction

Process resulting in the production of genetically identical offspring from one parent. Only one parent, offspring are genetically identical to parent.

Advantages and disadvantages of AR

A: 1. Faster reproduction(doesnt require mate) 2. Consistent offspring (advantageous in a stable environment ) 3. Energy efficient (doesn’t waste energy searching for mates or making gametes) 4. No need for pollination
D: 1. No genetic diversity (bad in a changing environment, poopulatio may not adapt to new conditions) 2. Vulnerable to disease (since genetically identical, disease that spreads to one organism can affect whole population)

Sexual reproduction

Process involving the fusion of the nuclei of two gametes to form a zygote and the production of offspring that are genetically different from each other

Fertilisation

the fusion of the nuclei of gametes. Sperm and ovum, or pollen nucleus and ovum

Haploid and diploid

nuclei of gametes are haploid (23 chromosomes) and the nucleus of a zygote is diploid (46 chromosomes)

Advantages and disadvantages of SR

A: 1. Increased genetic diversity (more adaptable to changing environemnt) 2. Less vulnerable to disease (can withstand disease) D: 1. Requires fusion of 2 gametes (requires time and energy for mate) 2. Slower process (reducing speed of reproduction and low production yields)

Sexual reproduction in plants

Typically contain both male (stamen) and female (carpel) reproductive parts. Male gametes are in pollen grains and female gametes are in ovum.

Functions of flower

Sepal: Protects the unopened flower

Petal: Brightly coloured in insect-pollinated flowers to attract insects

Anther: Contains pollen (the male sex cells)

Filament: Supports the anther

Stigma: The sticky surface that catches pollen

Style: Links stigma to ovary

Pollination

Transfer of pollen grains from anther to stigma. Insects or wind.

Insect-pollinated flowers

Petals: large & bright to attract insects

Pollen: Moderate in number, Large, sticky & spiky

Stigma: sticky and inside the flower

Anther: inside the flower, firmly attached

Scent & Nectar: is present to attract insects

Wind-pollinated flowers

Petals: small & dull

Stigma: feathery and outside the flower

Pollen: Large amounts, Smooth, small & light
Scent & Nectar: absent

Anther: outside the flower, swinging loose

Self-pollination

transfer of pollen grains from the anther of a flower to the stigma of the same flower or a different flower on the same plant. Reduces genetic variation and limits adaptability of offspring to changing environment conditions

Cross-pollination

transfer of pollen grains from the anther of a flower to the stigma of a flower on a different plant of the same species. Increases genetic variation but depends on pollinators. Wind pollinated plants are not affected

Fertilisaiton in flowers

Pollen nucleus fuses with an ovule nucleus. 1. Pollgen grains lands on stigma. 2. Pollen tube begins to grow down style until it enters ovule through micropyle. 3. Pollen nucleus moves down pollen tube 4. Pollen nucleus fuses with ovum nucleus. Ovule develops into seed. Ovary wall develops into fruit.

Factors affecting seed germination

The beginning pf seed growth is known as germination. 1. Water: causes seed to expand and activates enzymes within embryo to initiate growth. 2. Oxygen: For respiration to release energy for growth. 3. Suitable temperature to increase rate of germination since enzyme-catalysed reactions are temperature dependent