Fruit Overview

Definition:

A fruit is a mature ovary of a flowering plant.

Functions:

• Aid in seed dispersal.

• Protect seeds.

• Control seed germination.

Evolution:

• Many types of fruits have evolved.

Fruit Development Process

1. The fertilization of the egg cell in the ovule occurs.

2. Fertilized egg divides to produce an embryo plantlet.

3. The ovule containing the plantlet matures into a seed.

4. The ovary matures into a fruit, defined as a ripened ovary.

Fruit Classification

Based on Structure:

• Dry vs. Fleshy: Fruits are classified as either dry or fleshy.

Type of Formation:

• Simple Fruit: Formed from one pistil of a flower.

• Aggregate Fruit: Formed from several pistils in a single flower.

• Multiple Fruit: Formed from several flowers growing together.

Misnomers in Fruit Terminology

• Common misunderstandings about fruits:

  • Gymnosperms such as juniper berries are not true fruits.

  • The peanut is a legume, not a true nut.

Types of Simple Fruits

Dry at Maturity:

• Legume: Splits along two sides to form two halves (e.g., pea, peanut).

• Follicle: Splits along one side (e.g., milkweed).

• Capsule: Splits in various ways (e.g., poppy, tulip).

Fleshy at Maturity:

• Drupe: Contains a stony inner layer (e.g., cherry, coconut).

• Pome: Has a core with seeds surrounded by papery ovary walls (e.g., apple, pear).

• Berry: Thin skin, usually many seeds (e.g., tomato, banana).

• Pepo: Berry with thick rind (e.g., watermelon, cucumber).

• Hesperidium: Berry with leathery skin (e.g., orange, lemon).

Aggregate Fruits

• Formed from several carpels in a single flower.

• Examples: Raspberry, Strawberry.

Multiple Fruits

• Formed from an entire inflorescence of flowers (e.g., pineapple, fig).

Accessory Fruits

• Fruits consisting of parts that are not derived solely from the ovary (e.g., pomes, pepos).

• Example of Accessory Tissue: The hypanthium in apples.

Pericarp Structure

The pericarp develops into three layers:

1. Exocarp: Outermost layer, often the epidermis.

2. Mesocarp: Middle layer, varies in thickness.

3. Endocarp: Inner layer, shows considerable variation.

Specific Types of Berries

• Berry: Fleshy with thin skin (e.g., kiwi).

• Pepo: Thick rinds (e.g., pumpkins).

• Hesperidium: Leathery skins (e.g., citrus fruits).

• Pomes: Majority of flesh from floral tube (e.g., apples).

• Aggregate drupe: Cluster of drupes from a single flower (e.g., raspberry).

Dry Dehiscent Fruits

• Legumes: Derived from a single carpel, splits open (e.g., peanuts).

• Silique: Splits along two sides, seeds on a central partition (e.g., radish).

• Follicles: Splits along one side, revealing seeds (e.g., milkweed).

• Capsules: Common fruit type, splits to release seeds (e.g., cotton).

Dry Indehiscent Fruits

• Achene: Single-seeded, small, dry fruit (e.g., sunflower).

• Nuts: Large single hardened achenes (e.g., acorns).

• Caryopsis: Pericarp tightly united with seed (e.g., corn).

• Samara: Dry indehiscent fruit with wing (e.g., maple).

Fruit Dispersal Methods

Seed Dispersal

• Plants produce many seeds; survival depends on appropriate conditions.

Mechanisms of Dispersal:

• Autochory: Self-dispersal (e.g., flinging seeds).

• Allochory: Dispersal aided by external factors (e.g., wind, water, animals).

Wind Dispersal

• Anemochory: Light seeds capable of flight (e.g., dandelions).

Water Dispersal

• Hydrochory: Fruits float due to air-filled cavities (e.g., coconuts).

Animal Dispersal

• Zoochory: Fruits dispersed by animals (e.g., berries).

  • Types:

    • Endozoochoric: Seeds eaten and excreted.

    • Epizoochoric: Seeds stick to animals.

    • Myrmecochory: Ant-assisted dispersal (e.g., violets).

False Fruits

• Fruits that are not derived solely from ovary (e.g., figs, gymnosperms).

Parthenocarpy

• Development of fruit without fertilization, resulting in seedless fruit.

Plant Identification

• Dichotomous Keys: Tool for identifying plants by branching choices (e.g., leaf arrangement).

Fruit Classification Keys

• Simple vs. Compound Fruits: Basic branching for classification.

• Categorization steps leading to specific fruit types.