AG 101: Crop Science - Lecture on Flowering and Reproduction

Importance of Flowers

• Flowers are crucial for plant reproduction, providing food sources such as fruits and seeds (e.g., apples, wheat, corn, soybeans).
• They have aesthetic value and contribute to plant identification and classification.
• Play a role in breeding and selection processes.

Flower Structure

• Dicot Flower Structure
  • Sepals (Calyx): Green leafy outer layer.
  • Petals (Corolla): Colored part of the flower.
  • Pistil: Female reproductive part containing stigma, style, and ovary.
  • Stamen: Male part with anther (pollen location) and filament.
• Grasses (Monocot)
  • Have a different structure, e.g., corn, wheat, barley.
  • Basic flowering unit includes florets enclosed by glumes.
  • Lack petals or sepals.

Types of Floral Arrangements

• Inflorescences: Cluster of flowers (e.g., sorghum).
• Spike: Wheat family (e.g., barley).
• Panicle: Oats, sorghum, rice - different arrangement.
• Raceme: Alfalfa, soybean, mustard - continuous growth with older flowers at the bottom.
• Umbel: Wild carrot, white clover - umbrella-shaped.
• Head: Sunflower, daisies - disc and ray flowers.
• Solitary: Individual flowers, e.g., cotton.

Flower and Reproduction Terminology

• Complete Flowers: Have all four basic parts (male & female parts, sepals, petals).
• Incomplete Flowers: Missing one or more parts.
• Perfect Flowers: Contain both pistil and stamen.
• Imperfect Flowers: Missing either pistil or stamen.
• Monoecious: Male and female flowers on the same plant (e.g., corn).
• Dioecious: Male and female flowers on separate plants (e.g., buffalo grasses).

Pollination

• Process: Transfer of pollen from anther to stigma.
• Self-Pollination: Pollen from the same flower.
• Cross-Pollination: Pollen from different flowers.
• Insect vs. Wind Pollination
  • Insect pollinated flowers: Bright petals, nectar.
  • Wind pollinated flowers: No petals or nectar, light pollen.

Double Fertilization

• Unique to flowering plants.
• Involves two fertilization events: Formation of zygote (2n) and endosperm (3n).
• Occurs between male and female gametophytes.

Breeding and Cross-Pollination

• Corn: Easy due to separate male and female parts.
• Wheat and Soybean: More complex due to the need to emasculate flowers.
• Cross Examples: Corn crossed with controlled pollen transfer, covering parts.

Strategies and Challenges

• Pollination Strategies
  • Self-pollinated crops: Wheat, barley, oats.
  • Cross-pollinated: Alfalfa, sunflowers.
• Impact on Crop Management
  • Understanding pollination helps increase yields.
  • Avoiding self-pollination in breeding programs.
• Environmental Factors
  • Stress effects: Drought, high temps, diseases.
  • Importance of pollinators: Bees for alfalfa, apple orchards.

Conclusion

• Understanding flower structure and pollination is crucial for crop science and agriculture.
• Questions and further study are encouraged for deeper understanding.