Asexual Reproduction in Plants

• Asexual reproduction in flowering plants involves a single parent, resulting in genetically identical offspring.
• This method ensures uniformity in traits.
• Asexual reproduction is notably faster than sexual reproduction.
• It proves especially advantageous in stable environments.

Types of Asexual Reproduction

• Natural vegetative reproduction involves new plants growing from modified vegetative parts.

Natural Vegetative Reproduction: Modified Stems

• Tubers are swollen, fleshy underground stems with buds (eyes), exemplified by the potato.
• Runners (stolons) are above-ground horizontal stems with nodes for new growth, seen in strawberries and Bermuda grass.
• Rhizomes are underground horizontal stems that produce new plants, such as ginger and turmeric.
• Bulbs consist of short underground stems with fleshy leaves for food storage, like onions and garlic.
• Corms are thickened underground stems with disc-like parts, such as taro (gabi) and gladiolus.

Natural Vegetative Reproduction: Other Forms

• Some plants produce new plantlets from leaf edges such as Kalanchoe.
• Suckers, or sprouts from roots, form new plants, as seen in apple and blackberry plants.

Artificial Propagation Methods

• These are human-aided asexual reproduction techniques.

• Methods include cutting, grafting, and tissue culture.

• This is faster and allows mass production of plants.

• Cutting involves planting a piece of stem, leaf, or root to grow a new plant, exemplified by sugarcane, pineapple, and ornamental plants.

• Grafting involves attaching a stem (scion) from one plant to the root-bearing part (stock) of another plant, commonly used for apple and orange trees.

• Tissue culture involves growing cells in a sterile medium to produce clones, often used for orchids and potatoes.

Sexual Reproduction in Flowering Plants

• Sexual reproduction in flowering plants involves the fusion of male and female gametes, leading to genetic variation.

Structure of a Flower

• Sepals protect the flower bud.
• Petals attract pollinators with color and scent.
• The stamen is the male part of the flower.
• The anther produces pollen grains, which contain male gametes.
• The filament holds up the anther.
• The carpel/pistil is the female part.
• The stigma is the sticky part that catches pollen.
• The style connects the stigma to the ovary.
• The ovary contains ovules that develop into seeds after fertilization.

Stages of Sexual Reproduction

Pollination

• Pollination: Transfer of pollen from the anther to the stigma.
• Self-pollination occurs when pollen from the same flower fertilizes the ovule.
• Cross-pollination occurs when pollen from a different flower fertilizes the ovule.
• Wind is a pollination agent: it uses light, small pollen (e.g., grass, wheat).
• Water is a pollination agent: it uses floating pollen (e.g., water plants).
• Animals are pollination agents such as insects, birds, and bats (e.g., bees, butterflies).

Fertilization

• Fertilization: The processes of pollen landing on the stigma, a pollen tube grows down the style into the ovary and the sperm cell fertilizes the egg, forming a zygote.
• A second sperm cell fuses with two polar nuclei to form the endosperm.
• The zygote develops into an embryo.
• The endosperm provides food for the embryo.

Seed and Fruit Formation

• After fertilization, the ovule becomes a seed, the ovary becomes a fruit, and petals and other parts wither and fall off.

Seed Dispersal

• Seed dispersal is the movement of seeds away from the parent plant, preventing overcrowding and competition.
• Wind dispersal involves lightweight, winged seeds (e.g., dandelion, maple).
• Water dispersal involves floating seeds (e.g., coconut).
• Animal dispersal involves seeds being eaten and excreted (e.g., berries, cherries).
• Explosive mechanisms use seed pods that burst open (e.g., peas).