Flower Structure Quiz Covering Chapters 5-7

Announcements

• Online practical scheduled.
• Quiz on 18 September.
• Submission of drawing books on 19 & 20 September.
• Test 2: 12 September 2024 at 17h00, venues KA & KB, same format as Test 1.
• Scope of Test 2: Chapters 5, 6, and part of 7 (up to flowering).

Flower Structure

• A flower is a modified shoot primarily for reproduction, consisting of four whorls:
  • Calyx: Composed of sepals that protect the young flower (green).
  • Corolla: Made of petals that attract pollinators (colored).
  • Androecium: Consists of stamens (anther and filament) that produce male gametes.
  • Gynoecium: Comprises the pistil or carpels (stigma, style, ovary) which bear ovules.
• Tepals occur when sepals and petals look identical or are fused.

Reproductive Organs

• Male sex organs: Stamens (anther produces pollen, filament supports anther).
• Female sex organs: Carpels/pistil (ovary holds ovules; stigma is the pollen receptor; style connects stigma to ovary).

Non-Reproductive Floral Organs

• Sepals: Outer whorl that protects flower buds.
• Petals: Inner whorl that attracts pollinators.
• Tepals: Indistinguishable sepals and petals.

Flower Classification

• Complete flower: All four whorls present, whereas incomplete flowers lack one or more.
• Perfect flower: Contains both male and female parts; imperfect flowers have only one.
• Monoecious species possess both types of flowers on the same plant; dioecious species have them on separate plants.
• Actinomorphic (regular): Radially symmetrical; zygomorphic (irregular): Bilaterally symmetrical.

Coalescence and Adnation

• Coalescence: Joining of members within the same whorl.
  • Synsepaly: Joined sepals; aposepaly: free sepals.
  • Synpetaly: Joined petals; apopetaly: free petals.
• Adnation: Joining of members from different whorls.
  • Hypogynous: Parts below ovary; perigynous: ovary within a hypanthium; epigynous: parts above ovary.

Carpels and Placentation

• Carpels: Modified leaves forming cavities for ovules.
• Locules: Cavities within the ovary (unilocular, bilocular, trilocular).
• Placenta: Area in the ovary where ovules attach, with different placentation patterns:
  • Parietal, Marginal, Axile, Free/central, Apical, and Basal placentation.

Inflorescences

• Flowers can be solitary or in clusters on an axis called the rachis.
• Inflorescence types are classified based on flower arrangement and attachment.

Types of Inflorescences

• Simple monopodial:

  • Raceme: Indeterminate growth with pedicels of equal lengths.
  • Spike: Unbranched with sessile flowers.
  • Catkin: Long and unisexual.
  • Spadix: Fleshy spike with separate staminate and pistillate flowers.
  • Umbel: Flowers from the same point on the peduncle.
  • Corymb: Flat-topped; oldest flowers are on long pedicels.
  • Capitulum: Disc-like with sessile flowers.

• Compound monopodial:

  • Panicle: Branched racemes; multiple flower clusters.
  • Compound Spike: Multiple sessile flower groups.
  • Compound Corymb: Branched axis leading to corymb-like clusters.
  • Compound Umbel: Shortened primary axis with flowers on branches.
  • Cyme: Main axis ends in a flower; oldest flower at the base.

Key Terms

• Determinate: Growth with a fixed endpoint; structures grow to a certain size.
• Indeterminate: Growth continues indefinitely, allowing for a range of flower ages on the same stem.