🍏 The Fruit

The fruit is a characteristic feature of flowering plants. It is a mature or ripened ovary, developed after fertilisation.It protects the seeds and helps in their dispersal.

Parthenocarpic Fruit: If a fruit is formed without fertilisation of the ovary, it is called a parthenocarpic fruit. Example: Banana.

🌿 Parts of a Fruit

A fruit typically consists of a pericarp (fruit wall) and seeds.

  • The pericarp is the wall of the fruit, which develops from the wall of the ovary. It can be dry or fleshy.

  • In fleshy fruits, the pericarp is often differentiated into three layers:

    1. Epicarp: The outer skin.
    2. Mesocarp: The middle, fleshy, edible part (in many fruits).
    3. Endocarp: The inner, often hard and stony, layer, covering surrounding seeds.

  • Seeds: Developed ovules.

True Fruit vs. False Fruit

  • True Fruit: A fruit that develops only from the ovary (e.g., Mango, Tomato).
  • False Fruit (Pseudocarp): A fruit in which other floral parts, such as the thalamus, also contribute to its formation, in addition to the ovary (e.g., Apple, Strawberry, Cashew). In these, the main edible part is the fleshy thalamus.

🌸 Types of Fruits

Fruits are broadly classified into three main categories:

  1. Simple Fruit: Develops from a single, monocarpellary or multicarpellary syncarpous ovary of a single flower (e.g., Mango, Pea, Tomato).
  2. Aggregate Fruit: Develops from a multicarpellary, apocarpous (free carpels) ovary of a single flower. Each carpel develops into a fruitlet, forming a cluster (e.g., Strawberry, Raspberry).
  3. Composite Fruit (Multiple Fruit): Develops from a complete inflorescence (e.g., Pineapple, Fig, Mulberry).

🍑 The Drupe

A drupe is a type of simple, fleshy fruit where the pericarp is well-differentiated.

  • It develops from a monocarpellary, superior ovary.
  • Epicarp: Forms the thin outer skin.
  • Mesocarp: Is fleshy and edible (as in Mango).
  • Endocarp: Is hard and stony, forming the 'stone' that encloses the seed (as in Mango, Plum, Cherry, Peach).
  • In Coconut, which is also a drupe, the mesocarp is fibrous (not fleshy), and the endocarp is stony. The edible part is the endosperm of the seed.

🍑 Simple Fruits

1️⃣ Fleshy Fruits: Entire pericarp or parts remain fleshy.

  • Drupe: One-seeded fruit with stony endocarp (Mango, Coconut).
  • Berry: Entire pericarp edible (Tomato, Banana).
  • Pome: Fleshy part from thalamus (Apple, Pear).

2️⃣ Dry Fruits: Pericarp becomes dry at maturity.

  • Dehiscent: Split open to release seeds (Pea, Mustard).
  • Indehiscent: Do not split (Sunflower).

🌾 The Seed

The seed is the final product of sexual reproduction in angiosperms. It is a fertilised ovule. Seeds are typically formed inside fruits.

Structure of a Seed

A seed generally consists of:

  1. Seed Coat: The outermost protective covering. It has two layers: the outer testa and the inner tegmen. The seed is attached to the fruit through a scar called the hilum. Above the hilum is a small pore called the micropyle, which facilitates the entry of water and oxygen during germination.
  2. Embryo: Enclosed by the seed coat, the embryo consists of an embryonal axis and one or two cotyledons (seed leaves). The cotyledons are often fleshy and full of reserve food materials.
  3. Endosperm: In many seeds, there is a food-storing tissue called the endosperm, which is a product of triple fusion.

Types of Seeds (based on Endosperm)

  1. Non-albuminous (or Ex-albuminous): Seeds that have no residual endosperm at maturity because it has been completely consumed by the developing embryo. The food is stored in the cotyledons. Examples: Pea, Groundnut, Bean (most dicots).
  2. Albuminous (or Endospermous): Seeds that retain a part of the endosperm at maturity, as it is not completely used up. The cotyledons are often thin. Examples: Castor (dicot), Maize, Wheat, Rice (most monocots).

🌱 Parts of a Dicotyledonous Seed (e.g., Pea, Bean)

  • Seed Coat: Composed of testa (outer) and tegmen (inner).
  • Embryo: Consists of an embryonal axis and two cotyledons.
  • Cotyledons: Fleshy and store food.
  • Hilum: Scar where seed was attached to fruit wall.
  • Micropyle: Tiny pore allowing water absorption.
  • Embryonal Axis: Has two ends:
    1. Radicle: The lower end, which develops into the root system (primary root).
    2. Plumule: The upper end, which develops into the shoot system.
  • Endosperm: In seeds like gram, bean, and pea, the endosperm is absent at maturity (non-albuminous). In seeds like castor, the endosperm is present and stores food (albuminous).

🌾 Monocotyledonous Seed (e.g., Maize)

  • General: Most monocot seeds are albuminous (endospermous), e.g., maize, cereals. (Exception: Orchids are non-albuminous).
  • Seed Coat: Membranous and generally fused with the fruit wall (pericarp). This type of fruit/seed is called a caryopsis.
  • Endosperm: The bulky part of the seed, storing food. It is separated from the embryo by a proteinaceous layer called the aleurone layer.
  • Embryo: Small, situated in a groove at one end of the endosperm. It consists of:
  1. Scutellum: One large, shield-shaped cotyledon, appressed to the endosperm to absorb nutrients.
  2. Embryonal Axis: Contains the plumule and radicle.
  3. Coleoptile: A protective sheath covering the plumule (shoot apex).
  4. Coleorhiza: A protective sheath covering the radicle (root apex).

🌼 Differences Between Dicot and Monocot Seeds

Feature Dicot Seed Monocot Seed
Cotyledons Two One
Endosperm Usually absent Present
Example Pea Maize

🌸 Functions of Fruits and Seeds

  • Protection of embryo.
  • Aid in dispersal.
  • Storage of food.
  • Perennation and germination under favorable conditions.

💡 Questions and Answers

Q1. What is parthenocarpy? Give an example.

A1. Development of fruit without fertilization (e.g., Banana).

Q2. Define a drupe. Give two examples.

A2. One-seeded fruit with stony endocarp, e.g., Mango, Coconut.

Q3. Distinguish between monocot and dicot seeds.

A3. Dicot: two cotyledons, endosperm absent (Pea). Monocot: one cotyledon, endosperm present (Maize).

Q4. Describe the fruit of a Mango.

A4. The fruit of a mango is a drupe (a simple fleshy fruit). In a mango:

  • The epicarp is the thin outer skin.
  • The mesocarp is the thick, fleshy, yellow, edible pulp.
  • The endocarp is the hard, stony 'pit' or 'stone' inside which the seed is located.

Q5. Describe the fruit of a Coconut. Which part is edible?

A5. The fruit of a coconut is also a drupe.

  • The epicarp is the smooth, greenish-yellow outer skin.
  • The mesocarp is the thick, fibrous layer (which coir is made from), not fleshy.
  • The endocarp is the hard, stony shell that encloses the seed. The edible part of the coconut is the endosperm (the white 'meat' and the coconut water) which is part of the seed, not the pericarp.

Q6. Differentiate between albuminous and ex-albuminous seeds. Give one example of each.

A6.

  • Albuminous (Endospermous): Seeds that retain the endosperm at maturity as a food storage tissue. Example: Maize, Wheat, Castor.
  • Ex-albuminous (Non-endospermous): Seeds where the endosperm is completely consumed by the embryo during development. Food is stored in the fleshy cotyledons. Example: Pea, Gram, Bean, Groundnut.

Q7. What are the coleoptile and coleorhiza? What is their function?

A7. These are protective sheaths found in the embryo of monocot seeds like maize.

  • Coleoptile: A hollow, conical sheath that encloses and protects the plumule (young shoot apex) as it emerges through the soil during germination.
  • Coleorhiza: An undifferentiated sheath that encloses and protects the radicle (embryonic root) and root cap.

Q8. What is the scutellum in a maize seed, and what is its function?

A8. The scutellum is the single, large, shield-shaped cotyledon in a monocot (like maize or grass) embryo. It is located laterally to the embryonal axis. Its primary function is to absorb digested nutrients from the endosperm and transfer them to the growing embryo during germination.