Slide 1

Reproduction

• Process by which new organisms of the same species are produced
• Essential for the survival and continuation of a species
• Two types: asexual and sexual reproduction

Slide 2

Asexual Reproduction

• Involves only one parent
• Offspring are genetically identical to the parent
• Methods include binary fission, budding, and vegetative propagation

Slide 3

Sexual Reproduction

• Involves two parents
• Offspring inherit traits from both parents
• Essential for genetic variation and adaptation to changing environments

Slide 4

Sexual Reproduction in Flowering Plants

• Pollination is the transfer of pollen from the male reproductive organs to the female reproductive organs
• Fertilization is the fusion of male and female gametes to form a zygote
• Development of seed is a result of fertilization and leads to the formation of fruit

Slide 5

Development of Seed

• After fertilization, the zygote undergoes divisions and develops into an embryo
• The embryo is protected by the seed coat, which provides a protective covering
• The seed contains the embryo, food reserves, and a protective seed coat

Slide 6

Parts of a Seed

• Seed coat: Outer protective layer of the seed
• Embryo: Developing plant inside the seed
• Cotyledons: Structures that store food for the developing plant
• Radicle: Embryonic root
• Plumule: Embryonic shoot

Slide 7

Germination of Seeds

• Germination is the process by which a seed grows into a new plant
• Requires favorable conditions such as water, oxygen, and suitable temperature
• During germination, the radicle emerges first, followed by the plumule

Slide 8

Types of Pollination

• Self-pollination: Pollen from the anther is transferred to the stigma of the same flower or another flower on the same plant
• Cross-pollination: Pollen is transferred from the anther of one flower to the stigma of another flower on a different plant

Slide 9

Agents of Pollination

• Wind: Pollen is light and can be carried by wind to reach the stigma of other flowers
• Insects: Bees, butterflies, and other insects transfer pollen as they visit flowers in search of nectar
• Birds: Certain birds, such as hummingbirds, feed on nectar and transfer pollen while doing so

Slide 10

Structure of a Flower

• Sepals: Outermost part of the flower, protects the flower bud
• Petals: Attract pollinators with their color and fragrance
• Stamen: Male reproductive organ consisting of anther and filament
• Pistil: Female reproductive organ consisting of stigma, style, and ovary

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Slide 11

Modes of Sexual Reproduction

• Majority of flowering plants reproduce sexually
• Self-fertilization: Transfer of pollen from the anther to the stigma of the same flower
  • Example: Pea plants
• Cross-fertilization: Transfer of pollen from the anther of one flower to the stigma of another flower on a different plant
  • Example: Apple trees

Slide 12

Process of Fertilization

• Pollen grain lands on the stigma of a flower
• Pollen tube grows from the pollen grain down through the style into the ovary
• Male gametes travel through the pollen tube to reach the female gametes in the ovule
• Fusion of male and female gametes results in fertilization and formation of a zygote

Slide 13

Development of Embryo

• After fertilization, the zygote undergoes cell divisions to form an embryo
• The embryo consists of an embryonic root (radicle), an embryonic shoot (plumule), and one or two cotyledons
• Cotyledons provide nourishment to the developing embryo
• Different angiosperm species may have different numbers and arrangements of cotyledons

Slide 14

Development of Endosperm

• Endosperm is a nutritive tissue that surrounds and nourishes the embryo in the seed
• In some plants, endosperm is formed as a result of fusion of the male and female nuclei without fertilization
• In other plants, endosperm is formed as a result of fertilization
• Examples: Maize, coconut

Slide 15

Types of Endosperm

• Nuclear endosperm: Nucleus divides repeatedly without cell division, resulting in a multinucleate cell
• Cellular endosperm: Nucleus divides and cell walls form around each nucleus, resulting in a multicellular endosperm
• Examples: Wheat, coconut

Slide 16

Components of Fruit

• Ovary wall develops into the fruit after fertilization
• Fruit protects the enclosed seeds and aids in seed dispersal
• Pericarp: The wall of the fruit, consists of three layers: exocarp, mesocarp, and endocarp
• Examples: Apple, mango, tomato

Slide 17

Types of Fruits

• Simple fruit: Develops from a single ovary of a single flower
  • Examples: Tomato, pea, cherry
• Aggregate fruit: Develops from many ovaries of a single flower
  • Examples: Raspberry, blackberry
• Multiple fruit: Develops from many ovaries of many flowers in an inflorescence
  • Examples: Pineapple, fig

Slide 18

Seed Dispersal

• Seed dispersal is the process by which seeds are spread away from the parent plant
• Important for preventing competition for resources and for colonization of new areas
• Methods of seed dispersal include wind, water, animals, and self-dispersal

Slide 19

Methods of Seed Dispersal

• Wind dispersal: Seeds have adaptations such as wings or parachutes to be carried by wind
• Water dispersal: Seeds have adaptations to float in water and be carried by currents
• Animal dispersal: Seeds have adaptations to be carried by animals through ingestion or attachment
• Self-dispersal: Seeds have mechanisms to forcibly discharge or jump away from the parent plant

Slide 20

Germination Requirements

• For germination to occur, seeds require suitable conditions:
  • Adequate moisture for hydration
  • Proper temperature for enzyme activity
  • Sufficient oxygen for respiration
  • Suitable light conditions for certain seeds
• Factors affecting seed germination include seed dormancy, soil composition, and pH levels

Slide 21

Seed Dormancy

• Seed dormancy is a condition in which a viable seed fails to germinate even when provided with favorable conditions
• It helps the plant avoid germination during unfavorable seasons or conditions
• Examples of seed dormancy mechanisms:
  • Hard seed coat that requires scarification (physical or chemical damage) for water absorption
  • Chemical inhibitors that prevent germination until specific conditions are met

Slide 22

Scarification

• Scarification is the process of breaking or weakening the seed coat to improve water absorption and break seed dormancy
• Methods of scarification include:
  • Physical scarification: Abrasion of the seed coat through rubbing or sanding
  • Chemical scarification: Treating the seed coat with acid or other chemicals to soften or thin it
• Examples of seeds that require scarification for germination: Mimosa pudica, lupin seeds

Slide 23

Seed Germination and Factors Affecting It

• Seed germination is the resumption of growth of the embryo after a period of dormancy
• Factors affecting seed germination:
  • Water availability and hydration of the seed
  • Temperature: Optimal temperature ranges vary for different species
  • Oxygen availability for cellular respiration
  • Light requirements: Some seeds require light for germination, while others need darkness

Slide 24

Photoblastic Seeds

• Photoblastic seeds exhibit different responses to light during germination
• Positive photoblastic seeds require light for germination
  • Examples: Lettuce, petunia
• Negative photoblastic seeds require darkness for germination
  • Examples: Tomato, potato

Slide 25

Germination Process

1. Imbibition: Absorption of water by the seed, causing it to swell and activate enzymes
2. Activation of enzymes: Enzymes break down stored food reserves in the cotyledons or endosperm
3. Growth of radicle: Emergence of the radicle, which develops into the root
4. Growth of plumule: Emergence of the plumule, which develops into the shoot
5. Development of true leaves: The plumule develops into true leaves, and the plant starts photosynthesis

Slide 26

Germination in Monocots and Dicots

• Monocots: Have one cotyledon (e.g., maize, wheat)
  • The cotyledon remains underground during germination
  • The first leaf emerges directly from the coleoptile
• Dicots: Have two cotyledons (e.g., beans, peas)
  • The cotyledons emerge above ground during germination
  • The first leaf emerges directly from between the cotyledons

Slide 27

Significance of Seed Germination

• Seed germination is essential for the survival and reproduction of plants
• It allows the plant to resume growth and develop into a mature plant
• Seed germination contributes to the overall biodiversity and ecological balance of an ecosystem
• It plays a crucial role in agricultural practices and crop production

Slide 28

Seedling Establishment

• After seed germination, the seedling undergoes further growth and development to establish itself as a mature plant
• Factors affecting seedling establishment:
  • Availability of light, water, and nutrients
  • Competition with other plants for resources
  • Predation or herbivory by animals
  • Environmental factors such as temperature and humidity

Slide 29

Growth and Development of Plants

• Plants exhibit indeterminate growth, meaning they continue to grow throughout their lifespan
• Factors influencing plant growth and development:
  • Environmental factors: Light, temperature, water, nutrients
  • Hormones: Plant hormones regulate growth, development, and responses to stimuli
  • Genetic factors: Genetic makeup determines growth patterns, flowering, and fruiting

Slide 30

Key Terms

• Reproduction
• Asexual reproduction
• Sexual reproduction
• Pollination
• Fertilization
• Zygote
• Embryo
• Seed coat
• Cotyledons
• Radicle
• Plumule
• Germination
• Photoblastic
• Monocots
• Dicots
• Seed dormancy
• Scarification
• Seedling establishment
• Indeterminate growth