Slide 1
- Reproduction
- Sexual Reproduction in Flowering Plants
Slide 2
- Reproduction
- Process by which new individuals of the same species are produced
- Types of Reproduction
- Sexual Reproduction
- Asexual Reproduction
Slide 3
- Sexual Reproduction
- Involves the fusion of gametes
- Genetic variation in offspring
- Requires the involvement of male and female reproductive organs
Slide 4
- Sexual Reproduction in Flowering Plants
- Structure of a Flower
- Sepals, petals, stamens, and pistil
- Pistil
Slide 5
- Sexual Reproduction in Flowering Plants
- Pollination
- Transfer of pollen from anther to stigma
- Can be self-pollination or cross-pollination
- Fertilization
- Fusion of the male and female gametes
Slide 6
- Self Incompatibility
- Mechanism that prevents self-fertilization in flowering plants
- Types of Self Incompatibility Systems
- Gametophytic Self Incompatibility (GSI)
- Sporophytic Self Incompatibility (SSI)
Slide 7
- Gametophytic Self Incompatibility (GSI)
- Controlled by the genotype of the pollen grains
- Pollen with the same allele as the stigma is rejected
- Example
Slide 8
- Sporophytic Self Incompatibility (SSI)
- Controlled by the genotype of the stigma
- Pollen with the same allele as the stigma is rejected
- Example
- Solanaceae family, including tomato and potato
Slide 9
- Molecular Basis of Self Incompatibility
- Recognition and rejection mechanisms
- Involves specific recognition proteins on the stigma surface
- Example
- SI-RLK (Self-Incompatibility Receptor-Like Kinase) gene in Brassica and Papaver
Slide 10
- Significance of Self Incompatibility
- Prevents inbreeding depression
- Promotes genetic diversity
- Helps maintain a healthy and adaptable population
Slide 11
- Pollination Mechanisms
- Wind-Pollinated Flowers
- Small, inconspicuous flowers
- Large, feathery stigma to maximize pollen capture
- Abundant pollen production
- Examples: grasses, conifers
- Insect-Pollinated Flowers
- Brightly colored petals, fragrance, and nectar to attract insects
- Sticky or feathery stigma to facilitate pollen transfer
- Examples: roses, lilies
- Bird-Pollinated Flowers
- Brightly colored, tubular flowers with no fragrance
- Large, sticky stigma to prevent pollen loss
- Examples: hummingbird-pollinated flowers
Slide 12
- Double Fertilization in Angiosperms
- Unique to flowering plants
- Involves the fusion of two male gametes with two female gametes
- One male gamete fertilizes the egg cell to form the zygote
- The other male gamete fuses with the two polar nuclei to form the endosperm (triploid)
Slide 13
- Double Fertilization in Angiosperms (contd.)
- Endosperm Development
- Provides nourishment to the developing embryo
- Stores nutrients for seed germination
- Examples: wheat, rice, corn
- Significance of Double Fertilization
- Ensures the synchrony between embryo and endosperm development
- Optimizes resource allocation for seed growth and germination
Slide 14
- Development of Fruit
- Ovary wall thickens and matures after fertilization
- Forms the fruit, which protects the developing seeds
- Types of Fruits
- Simple fruits: derived from a single ovary
- Aggregate fruits: derived from several ovaries in a single flower
- Examples: raspberry, blackberry
- Multiple fruits: derived from several flowers in an inflorescence
Slide 15
- Seed Dispersal
- Importance of Seed Dispersal
- Prevents competition among parent and offspring
- Colonizes new habitats
- Examples: wind, water, animals
- Methods of Seed Dispersal
- Wind: dandelion seeds, maple seeds
- Water: coconut seeds, water lilies
- Animals: burrs sticking to fur, consumed and excreted seeds
Slide 16
- Germination of Seeds
- Activation of dormant seed to resume growth
- Required Conditions for Germination
- Water availability
- Adequate temperature
- Oxygen availability
- Steps of Seed Germination
- Water uptake by the seed
- Activation of enzymes for metabolism
- Emergence of the radicle (embryonic root)
Slide 17
- Germination of Seeds (contd.)
- Seed Germination Process
- Radicle develops into the primary root
- Shoot system grows above the ground
- Cotyledons (seed leaves) function as temporary storage organs
- Leaves start photosynthesis for energy production
- Examples
- Monocots: one cotyledon (e.g., maize, wheat)
- Dicots: two cotyledons (e.g., beans, peas)
Slide 18
- Significance of Seed Germination
- Replenishes plant populations
- Establishes new plants in favorable environments
- Enables plant survival and reproduction
- Examples: forests, agricultural fields
Slide 19
- Factors Affecting Reproduction in Flowering Plants
- Environmental Factors
- Temperature: affects germination, flowering, and pollen viability
- Light: regulates flowering and direction of growth
- Water availability: crucial for seed germination
- Biotic Factors
- Pollinators: essential for sexual reproduction in insect-pollinated flowers
- Herbivores: can damage flowers, reduce seed production
Slide 20
- Summary
- Sexual Reproduction in Flowering Plants
- Involves the fusion of gametes
- Pollination and fertilization are key steps
- Self-incompatibility systems prevent self-fertilization
- Double Fertilization and Fruit Development
- Unique to angiosperms
- Forms the zygote and endosperm
- Ovary wall develops into a protective fruit
- Seed Dispersal and Germination
- Ensures effective colonization and growth of offspring
- Germination requires water, temperature, and oxygen availability
Slide 21
- Environmental Factors Affecting Reproduction (contd.)
- Edaphic Factors
- Soil characteristics: affect nutrient availability for plant growth and reproduction
- Soil pH: influences nutrient uptake and availability
- Climatic Factors
- Rainfall: affects seed germination and flowering
- Humidity: influences pollen viability and pollen tube growth
- Wind: aids in pollination and seed dispersal
Slide 22
- Biotic Factors Affecting Reproduction
- Mutualistic Interactions
- Pollinators: bees, butterflies, birds
- Example: Bee pollinating a flower
- Dispersers: animals that eat fruits and disperse seeds
- Example: Squirrel burying an acorn
- Antagonistic Interactions
- Herbivores: animals that eat plant tissues
- Example: Caterpillar feeding on leaves
- Pathogens: microorganisms causing disease in plants
- Example: Fungal infection on a plant leaf
Slide 23
- Hormonal Regulation of Reproduction
- Plant Hormones Involved
- Auxins: promote flowering, fruit development, and seed germination
- Gibberellins: stimulate flowering and seed germination
- Cytokinins: influence cell division and differentiation
- Abscisic Acid: inhibits seed germination
- Ethylene: promotes fruit ripening and leaf senescence
Slide 24
- Hormonal Regulation of Reproduction (contd.)
- Photoperiodism
- Photoperiod: duration of light and dark periods in a day
- Influences flowering in many plants
- Short-Day Plants: flower when the day length is shorter than a critical value
- Long-Day Plants: flower when the day length is longer than a critical value
- Day-Neutral Plants: flower independently of day length
Slide 25
- Gametogenesis
- Formation of male and female gametes
- Male Gametogenesis: Spermatogenesis
- Occurs in the testes
- Spermatogonia → Primary spermatocytes → Secondary spermatocytes → Spermatids → Spermatozoa
- Female Gametogenesis: Oogenesis
- Occurs in the ovaries
- Oogonia → Primary oocytes → Secondary oocyte + Polar body → Ovum
Slide 26
- Embryogenesis
- Embryo Development in Angiosperms
- Occurs after fertilization
- Zygote → Embryo
- Embryo development involves different stages, including:
- Globular stage
- Heart-shaped stage
- Torpedo stage
- Cotyledonary stage
- Mature embryo stage
Slide 27
- Structure of a Seed
- Seed Coat: outer protective layer
- Endosperm: provides nourishment to the developing embryo
- Embryo: consists of embryonic leaves (cotyledons) and a radicle
- Examples: maize seed, bean seed
Slide 28
- Regulation of Reproduction in Plants
- Photoperiodic Control
- Flowering is regulated by the relative duration of light and dark periods
- Controlled by the photoreceptor protein Phytochrome
- Vernalization
- Exposure to low temperatures stimulates flowering
- Overcomes seed dormancy and promotes flowering
Slide 29
- Economic Importance of Reproduction in Plants
- Agriculture
- Crop production and improvement rely on plant reproduction
- Techniques like artificial pollination and hybridization are used to improve crop traits
- Horticulture
- Flower production and landscaping depend on plant reproduction
- Techniques like grafting and tissue culture are used for propagation
- Conservation
- Conservation and preservation of rare and endangered plant species
- Ex situ conservation methods involve seed banking and tissue culture preservation
Slide 30
- Conclusion
- Sexual reproduction in flowering plants involves the fusion of gametes and leads to genetic diversity in offspring.
- Self-incompatibility systems prevent self-fertilization and maintain genetic variability within populations.
- Pollination, double fertilization, and fruit development are essential processes in the reproductive cycle of angiosperms.
- Seed dispersal and germination ensure the establishment and survival of plant offspring in new habitats.
- Factors like environmental conditions, biotic interactions, and hormonal regulation influence plant reproduction.
- Understanding the mechanisms of plant reproduction is crucial for agriculture, horticulture, and conservation efforts.