Plant Reproduction: Asexual Reproduction

• Plant reproduction occurs through asexual and sexual means.

Asexual Reproduction

• Asexual reproduction involves one parent and produces genetically identical offspring.
• Binary fission in bacteria results in exact genetic copies.
• Vegetative propagation uses bulbs or tubers where budding creates new plants.
• Runners, such as those in strawberry plants, are side shoots with plantlets that grow roots and become separate plants.
• Spore formation is a method of asexual reproduction in fungi.
• Cuttings involve placing cut shoots in water or soil to grow new plants.

Advantages and Disadvantages of Asexual Reproduction in Wild Species

• Rapid population growth can occur.
• Limited genetic variation exists within the population.
• Environments can be exploited quickly.
• Vulnerability to habitat changes is a risk.
• Reproduction is time and energy efficient.
• Vulnerability to diseases is a risk.
• Reproduction is completed faster than sexual reproduction.
• Evolution is a slow process.

Advantages and Disadvantages of Asexual Reproduction in Crop Plants

• Crops exhibit desired characteristics.
• Inability to adapt to climate changes is a disadvantage.
• Faster crop production is achieved.
• Human input is required.
• All crops share the same characteristics.
• Vulnerability to diseases from the parent plant is a concern.
• It is a low-cost method.
• Vulnerability to disease or pests can cause financial losses.

Sexual Reproduction

• Sexual reproduction involves the fusion of gamete nuclei to form a zygote, producing genetically different offspring.
• Fertilization is the fusion of gamete nuclei.
• A gamete is a sex cell, like sperm or ovum.
• Gametes have a haploid nucleus, containing half the chromosomes of other body cells.
• Humans have 46 chromosomes; human gametes contain 23 chromosomes.
• A zygote formed from male and female gametes has 46 chromosomes, thus a diploid nucleus.
• Haploid cells have half the normal chromosome number (23 in humans).
• Diploid cells have the normal chromosome number (46 in humans).

Advantages and Disadvantages of Sexual Reproduction

• Genetic variation increases.
• Finding mates consumes time and energy.
• Species adapt to new environments.
• Two parents are needed.
• Disease spread is less likely.

Sexual Reproduction in Plants

• The carpel is the female reproductive structure.
• The stamen is the male reproductive structure

Flower Structure and Functions

• Sepals protect unopened flowers.
• Petals, brightly colored in insect-pollinated flowers, attract insects.
• Anthers produce and release pollen.
• Filaments support the anthers.
• Stigmas are the sticky tops of the female part of the flower that collect pollen grains.
• Styles are tubes connecting the stigma to the ovary.
• Ovaries contain ovules.
• Ovules contain female gametes.

Pollination

• Pollination transfers pollen grains from an anther to a stigma.
• Fertilization is the fusion of a pollen nucleus with an ovum nucleus.
• Germination is the start of seed growth.

Insect- vs Wind-Pollinated Flowers: Pollen

• Insect-pollinated flowers create large, heavy pollen with spikes or hooks.
• Wind-pollinated flowers produce small, lightweight pollen.

Structural Adaptations of Insect- vs Wind-Pollinated Flowers

• Insect-pollinated flowers feature large and brightly colored petals. Wind-pollinated flowers have petals that are small and dull.
• Insect-pollinated flowers produce scent and nectar to attract insects. Wind-pollinated flowers do not produce scent or nectar.
• Insect-pollinated flower anthers are help on stiff filaments. Wind-pollinated flower anthers are held on long filaments outside of the flower.
• Insect-pollinated flowers feature sticky stigmas. Wind-pollinated flowers feature feathery stigmas outside of the flower.

Factors Affecting Germination

• Water allows the seed to swell and activates enzymes for growth.
• Oxygen enables aerobic respiration, providing energy for germination.
• Warmth ensures optimum temperature for enzymes, improving germination.
• Seeds contain an embryo plant and cotyledons.
• The testa is the tough seed coat.
• Cotyledons are food stores.
• The micropyle is a hole where water enters.
• The plumule is the embryo shoot.
• The radicle is the embryo root, which emerges first.

Live Mass/Dry Mass Germination Trends

• Live mass increases as seeds absorb water.
• Dry mass decreases as energy is used for respiration but increases later due to photosynthesis.

Cross- vs Self-Pollination

• Cross-pollination transfers pollen from one plant to another of the same species.
• Self-pollination transfers pollen within the same flower or to another flower on the same plant.
• Self-pollination reduces genetic variety because gametes are genetically identical. Cross-pollination improves genetic variation but depends on pollinators.
• Pollen tube formation happens after pollination.
• A pollen tube grows from the pollen grain down the style to the ovary.
• Nuclei from pollen travel down the tube to the ovule and fuse with the female gamete nucleus.
• After fertilization, the ovule develops into a seed, and the ovary develops into a fruit.