Reproduction in Plants

Reproduction in Plants

• Living organisms reproduce to ensure the survival of their species through two primary modes: asexual and sexual reproduction.
• Asexual reproduction involves a single parent, where no gamete fusion occurs, while sexual reproduction involves two parents with the formation of male and female gametes.

Types of Asexual Reproduction

• Binary Fission: Common in bacteria like Chlorella. The parent cell divides into two identical daughter cells.
• Budding: Observed in yeast, where a new organism forms as a small outgrowth (bud) on the parent, eventually detaching to live independently.
• Fragmentation: Plants like Spirogyra break into smaller fragments, each capable of growing into a new individual.
• Spore Formation: Spores are produced by fungi and plants like mosses, which can be dispersed by wind or insects.
• Vegetative Propagation: New plants develop from vegetative parts such as roots, stems, or leaves, can occur naturally or artificially.

Natural Vegetative Propagation

• Reproduction by Stem: Plants like grass and mint produce runners, which develop new plants at their nodes.
• Reproduction by Root: Sweet potatoes have swollen roots with buds that can grow into new plants.

Advantages of Vegetative Reproduction

• Faster propagation time, ensuring quick spread in a small area.
• Retainment of desirable traits from the parent plant.

Artificial Vegetative Propagation Methods

• Cutting: Stems are cut and planted in moist soil to root and grow into new plants, used for sugarcane, roses, etc.
• Layering: A branch is bent to the ground, covered with soil, and once rooted, separated to grow independently.
• Grafting: A bud or shoot from one plant is attached to the stem of another related plant, requiring close contact of cambium layers for success.

Structure of a Typical Flower

• Calyx: Outermost whorl, consisting of sepals.
• Corolla: Second whorl made up of petals, often colorful and fragrant.
• Androecium: Third whorl, consisting of stamens (male reproductive part).
• Gynoecium: Innermost whorl, consisting of carpels (female reproductive part).

Pollination

• Transfer of pollen from the anther to the stigma of the same or a different flower.
• Self-pollination: Pollen transfer occurs within the same flower or between two flowers on the same plant.
• Cross-pollination: Involves pollen from different plants of the same species.

Agents of Pollination

• Insects: Help transfer pollen through nectar collection, enabling insect pollination.
• Wind: Certain plants produce large amounts of pollen, which can be carried to other flowers by the wind.

Characteristics of Pollination Agents

• Wind-pollinated flowers generally possess dull colors and exposed stigmas to facilitate pollen transfer.

Fertilization Process

• Following pollination, the pollen grain germinates and forms a pollen tube, which penetrates the ovule and releases male gametes for fusion with the egg cell, resulting in a zygote.
• The fertilized ovule develops into a seed, and the ovary develops into the fruit upon fertilization.

Artificial Pollination

• Manual transfer of pollen grains, practiced by plant breeders to develop new plant varieties with specific desired traits.

Key Flower Parts

• Ovary: Develops into fruit post-fertilization.
• Anther: Produces pollen grains.
• Stigma: Receives pollen during pollination.

Fill in the Blanks

• A flower with one type of sex organ is unisexual.
• A flower with both male and female organs is bisexual.
• Pollen transfer by wind is wind pollination.
• Male and female gamete fusion is fertilization.
• An ovule develops into a seed.
• An ovary develops into a fruit.