Plant Hormones and Seed Dispersal

Plant Hormones and Fruiting

• Auxins are plant hormones used to induce fruiting without fertilization.

Seed Dispersal

• Dispersal ensures survival by relocating seeds away from the parent plant, reducing competition.

Animal Dispersal

• Seeds are ingested by animals, passing through their intestines where digestive enzymes can aid germination.
• Examples include tomato and apple seeds, which require this process for germination.

Wind Dispersal

• Seeds must be lightweight and possess a large surface area to facilitate wind transport.
• Notable examples include sycamore and dandelion seeds.

Self-Dispersion

• Pea pods dry and develop lines of weakness, curling and splitting to eject seeds.
• Gorse exemplifies self-dispersing plants.

Water Dispersal

• Seeds contain air pockets to keep them buoyant, allowing for long-distance dispersal.
• The yellow water lily showcases this dispersal method.

Dormancy

• Dormancy is a period of reduced growth/metabolism despite suitable germination conditions.

Advantages of Dormancy

• Protects plants from adverse conditions that could harm new growth.
• Allows seeds to spread, reducing competition.
• Gives embryos time to mature until conditions improve.

Breaking Dormancy

• Seeds often have waterproof coatings (Testa) that prevent water entry, maintaining dormancy until conditions are favorable.

Seed Formation

• Post-fertilization, the ovule swells and toughens to form the seed coat.
• The zygote develops into a seed embryo, while the triploid endosperm becomes a food storage system.
• The integuments thicken to form the protective Testa.

Seed Structure

• Embryo: Develops into the new plant.
• Testa: Tough outer coat protecting the seed.
• Radicle: First root part to emerge.
• Plumule: Develops into the shoot.
• Cotyledons: Seed leaves that store food, can be one (monocots) or two (dicots).

Seed Types

• Endospermic seeds (e.g., maize, wheat) store food in the endosperm.
• Non-endospermic seeds (e.g., broad bean) store nutrients primarily in cotyledons.

Fruit Formation

• Fruits protect seeds and aid in dispersal.
• Seedless fruits, like watermelons, are developed through genetic selection or treatment to break seed dormancy.
• Chemical soaking can wash out inhibitors, and application of hormones can enhance fruit production.

Germination

• Germination is the process when a seed begins to grow.

Requirements for Germination

• Water: Acts as a solvent and medium for hormones/enzymes.
• Oxygen: Essential for aerobic respiration and energy production.
• Temperature: Necessary for enzyme activity.
• Food: Reserves in the seed provide energy for new tissue development.

Stages of Germination

• Emergence of the radicle forms the root.
• Plumule grows upwards to form the shoot, leading to initial weight loss.
• Leaves break the surface, initiating photosynthesis, and the plant starts gaining weight.
• Hypogeal Germination: Seed remains underground.
• Epigeal Germination: Seed grows above ground.

Asexual Reproduction

• Involves no gametes, resulting in genetically identical offspring to the parent plant.

Explore the role of plant hormones in inducing fruiting without fertilization. This quiz also covers the importance of seed dispersal methods, particularly animal dispersal, and how it aids in plant survival and germination processes.