Flowers, Fruits, and Seed

Introduction

Monocot vs. Dicot

  • Monocots: have floral parts in groups of 3.
  • Dicots: floral parts in groups of 4 or 5.

The flower

Whorls

  • Whorls - floral organs   * (sepals, petals, stamen, carpels)

  • (outside)Sepals → Petals → Stamen → Carpels (inside)

Male vs. Female

  • Androecium (male) - Stamen (filament (stem), anther hold pollen chambers that hold the pollen)
  • Gynoecium (Female) - carpel (stigma (top)) style (stem) ovary (swollen bulb), ovules (hold eggs))

Classification

  • Complete flowers have 4 whorls.
  • Incomplete flowers have 1 or more whorls missing
  • Perfect flowers contain stamens and carpels (monoecious)
  • imperfect flowers which are missing the stamen or the carpel (dioecious)
  • Monoecious: the plant has both sexes in the same flower
  • Dioecious: one plant has the stamen, a different one has carpel
  • Solitary flowers are single
  • Inflorescences (clusters) are groups of flowers on the same plant.

Pollination

  • Pollination: pollen is transferred from the anther to the stigma

  • Pollinators (vectors) determine flower, smell, look, and arrangement.   * wind pollinators are basic (no color or smell) with a wide umbrella arrangement   * Transferred by bees are usually blue or purple and have nector   * Transferred by birds are usually red and have nectar   * night-blooming flowers are usually white, to attract nocturnal insects   * some flowers (star-flower) smell like rotting meat to attract flies

  • Self-pollination: (same plant) advantages if well adapted, we are good.   * If the environment changes then we’re screwed.

  • Other plants of the same species (cross-pollination): lead to better variation and diversity

Fertilization

  • Pollen grains are formed in the pollen sacs and each grain has 2 sperm nuclei (vegetative and generative)
  • Each ovule has 8 nuclei, 3 of which are involved in fertilization (2 polar bodies and 1 egg).
  • Double Fertilization: (2 fusions) the endosperm (3n) forms when the 2 polar bodies and 1 sperm nuclei fuse (this occurs in the pollen tube (formed by vegetative)) and the zygote (2n) is formed when the egg and the other sperm fuse, this becomes the embryo.
  • The ovary becomes the fruit that holds the ovule which becomes the seed that holds the endosperm and the embryo

Fruit

Types of Fruit

  • Simple fruits were formed from single ovules.
  • Aggregate fruits were formed from multiple ovules.
  • Fleshy fruits are soft and juicy
  • Dry fruits are tough and woody or thin and papery
  • Dehiscent fruits split open at maturity and so release their seeds
  • Indehiscent fruits do not split they use other methods of dispersing their seeds
Simple Fleshy
  • Berries (not a strawberry/raspberry/blackberry), drupes, pepos, hesperidium, pomes
Aggregate Fruits
  • the strawberries, blackberries, and raspberry (basically multiple fruits all connected)
Multiple
  • pineapple (results from the fusion of ovaries of separate flowers in a cluster)
Simple Dry Dehiscent
  • Follicles, legumes, capsules
Simple Dry Indehiscent
  • achene (sunflower seed), grains, samara, nuts

Fruit Ripening

  • The fruit softens, transforms from acidic to sweet, and the color changes.
  • Fruit ripening is regulated by Ethylene gas which is a plant hormone released by ripening fruit.
  • This process can be hastened by manipulating ethylene levels.

Diet

  • Most of our calories we get from fruit and seeds.
  • Seed structure varies on monocot/dicot status.   * embryo: radicle, plumule, and cotyledon   * Endosperm - provides nourishment from plants and us (the main source of calories in grains)   * Seed coat (testa)
  • Grain is a one seeded-fruit where the seed coat and ovary are fused.
  • Mature seeds are dry and can be stored for long periods.
  • Immature seeds are soft and could still be in the pod.
  • Mature seeds must be rehydrated in order for us to eat them.
  • Mature dry seeds will germinate if placed in cool, damp soil
  • Some farmers may hold back some of their dry seeds to plant for the next season instead of eating them.
  • Other farmers simply buy new seeds.

Seed banks

  • Seed banks are used to ^^preserve genetic diversity^^ by preserving the germplasm in frozen temperatures.

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