Reproduction: Sexual Reproduction in Flowering Plants

• Difference between self and cross pollination
• Importance of sexual reproduction
• Introduction to the reproductive structures in flowering plants
• Overview of pollination and fertilization processes

Sexual Reproduction in Flowering Plants

• The fusion of male and female gametes
• Enhances genetic diversity
• Promotes adaptation in changing environments
• Example: A pollen grain (male gamete) fuses with an embryo sac (female gamete) to form a zygote in a flower.

Reproductive Structures in Flowering Plants

1. Male Reproductive Structure:
   • Stamen: anther and filament
   • Anther produces pollen grains
   • Filament supports the anther

2. Female Reproductive Structure:
   • Carpel: stigma, style, and ovary
   • Stigma receives the pollen grains
   • Style connects the stigma and ovary
   • Ovary contains ovules

• Example: In a rose flower, the stamen produces pollen grains and the carpel contains the ovary.

Pollination: Transfer of Pollen

• Self-pollination: transfer of pollen from anther to stigma of the same flower or different flowers of the same plant
• Cross-pollination: transfer of pollen from anther of one plant to the stigma of a different plant
• Example: Pollen from the anther of a sunflower can be transferred to the stigma of a different sunflower plant.

Self Pollination

• Occurs within the same flower or between flowers of the same plant
• No involvement of external agents in pollen transfer
• Example: Pea plants often undergo self-pollination, where the pollen from the anther is transferred to the stigma of the same flower.

Cross Pollination

• Requires a pollinating agent to transfer pollen
• Examples of pollinating agents:
  • Insects (bees, butterflies)
  • Birds (hummingbirds)
  • Wind (grasses, trees)
  • Water (aquatic plants)
• Example: Bees transfer pollen from one flower to another, facilitating cross-pollination in plants.

Advantages of Cross Pollination

1. Increased Genetic Variation:
   • Leads to better adaptation to changing environmental conditions
   • Increases chances of survival and reproduction

2. Prevents Inbreeding:
   • Reduces the risk of genetic disorders
   • Maintains genetic diversity in the population

• Example: Cross-pollination in plants helps in producing offspring with diverse traits, which enhances their ability to withstand environmental challenges.

Adaptations for Cross Pollination

• Production of large quantities of pollen grains
• Presence of attractive flowers with bright colors and sweet scent
• Nectar production to attract pollinators
• Production of feathery stigmas to capture wind-borne pollen
• Development of specialized structures to facilitate pollination, e.g., orchids with their intricate flower structures and mimicry.
• Example: The bright red color and sweet scent of flowers of a rose plant attract insects and birds, facilitating cross-pollination.

Pre-Fertilization Events in Cross Pollination

1. Pollen Transfer:
   • Pollen grains are deposited on the stigma

2. Pollen Germination:
   • Pollen grains grow a pollen tube that penetrates the stigma and style

3. Pollen Tube Growth:
   • Pollen tube grows towards the ovary where the ovules are located

• Example: A pollen grain lands on the stigma, germinates, and grows a pollen tube towards the ovary to reach the ovules.

Fertilization in Cross Pollination

• When the pollen tube reaches the ovary, it enters the ovule
• Fusion of male gametes (in pollen tube) with female gametes (in ovule)
• Formation of zygote and embryo
• Development of seed and fruit which aids in dispersal
• Example: In the fertilization process, the pollen tube delivers the male gametes to the ovule, resulting in the formation of a zygote and ultimately a seed.

Reproduction: Sexual Reproduction in Flowering Plants

• Difference between self and cross pollination
• Importance of sexual reproduction
• Introduction to the reproductive structures in flowering plants
• Overview of pollination and fertilization processes

Sexual Reproduction in Flowering Plants

• The fusion of male and female gametes
• Enhances genetic diversity
• Promotes adaptation in changing environments
• Example: A pollen grain (male gamete) fuses with an embryo sac (female gamete) to form a zygote in a flower.

Reproductive Structures in Flowering Plants

1. Male Reproductive Structure:
   • Stamen: anther and filament
   • Anther produces pollen grains
   • Filament supports the anther

2. Female Reproductive Structure:
   • Carpel: stigma, style, and ovary
   • Stigma receives the pollen grains
   • Style connects the stigma and ovary
   • Ovary contains ovules

• Example: In a rose flower, the stamen produces pollen grains and the carpel contains the ovary.

Pollination: Transfer of Pollen

• Self-pollination: transfer of pollen from anther to stigma of the same flower or different flowers of the same plant
• Cross-pollination: transfer of pollen from anther of one plant to the stigma of a different plant
• Example: Pollen from the anther of a sunflower can be transferred to the stigma of a different sunflower plant.

Self Pollination

• Occurs within the same flower or between flowers of the same plant
• No involvement of external agents in pollen transfer
• Example: Pea plants often undergo self-pollination, where the pollen from the anther is transferred to the stigma of the same flower.

Cross Pollination

• Requires a pollinating agent to transfer pollen

• Examples of pollinating agents:

  • Insects (bees, butterflies)
  • Birds (hummingbirds)
  • Wind (grasses, trees)
  • Water (aquatic plants)

• Example: Bees transfer pollen from one flower to another, facilitating cross-pollination in plants.

Advantages of Cross Pollination

1. Increased Genetic Variation:
   • Leads to better adaptation to changing environmental conditions
   • Increases chances of survival and reproduction

2. Prevents Inbreeding:
   • Reduces the risk of genetic disorders
   • Maintains genetic diversity in the population

• Example: Cross-pollination in plants helps in producing offspring with diverse traits, which enhances their ability to withstand environmental challenges.

Adaptations for Cross Pollination

• Production of large quantities of pollen grains
• Presence of attractive flowers with bright colors and sweet scent
• Nectar production to attract pollinators
• Production of feathery stigmas to capture wind-borne pollen
• Development of specialized structures to facilitate pollination, e.g., orchids with their intricate flower structures and mimicry.
• Example: The bright red color and sweet scent of flowers of a rose plant attract insects and birds, facilitating cross-pollination.

1. Pollen Transfer:
   • Pollen grains are deposited on the stigma

2. Pollen Germination:
   • Pollen grains grow a pollen tube that penetrates the stigma and style

3. Pollen Tube Growth:
   • Pollen tube grows towards the ovary where the ovules are located

• Example: A pollen grain lands on the stigma, germinates, and grows a pollen tube towards the ovary to reach the ovules.