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Fruit (plant structure)

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**Categories of Fruits:**
– Fruits are classified into three main anatomical categories: aggregate fruits, multiple fruits, and simple fruits.
– Aggregate fruits originate from a single compound flower and contain multiple ovaries or fruitlets (e.g., raspberries, blackberries).
– Multiple fruits develop from the fused ovaries of multiple flowers or inflorescence (e.g., fig, mulberry, pineapple).
– Simple fruits form from a single ovary and can have one or multiple seeds, which may be fleshy or dry.
– Fleshy fruits include berries, pomes, and drupes, while dry fruits encompass achenes, capsules, follicles, or nuts.

**Evolutionary History and Importance of Fruit Diversity:**
– Dry fruits existed before fleshy fruits, which evolved independently multiple times.
– Various plants employ diverse dispersal methods, with animal dispersal being effective but not significantly increasing dispersal distances.
– Minor changes in developmental regulatory genes can lead to substantial alterations in fruit anatomy.
– The diversity in fruit structures is vital for the continuity of plant populations.

**Anatomy of Simple Fruits:**
Fruit anatomy involves the internal structure where the pericarp forms the edible tissue around the seeds.
– Berries and drupes have edible pericarp, while in citrus and stone fruits, only certain layers are edible.
– Accessory fruits like strawberries have edible parts developed from tissues other than the ovary.

**Pericarp Layers in Fruits:**
– In fleshy fruits, the pericarp typically comprises three layers: epicarp (outermost), mesocarp (middle), and endocarp (inner).
– Epicarp forms the tough outer skin of the fruit and contains various components like essential oils and pigments.
– Mesocarp, the fleshy middle layer, is crucial for fruit development and flavor.
– Endocarp, the inner layer, varies in thickness and hardness in different fruits, surrounding the seeds in nuts and being membranous in citrus fruits.

**Anatomy of Grass Fruits:**
– Grass grains are caryopsis fruits where the pericarp and seed coat are fused, as seen in wheat and barley.
– The dead pericarp in grass fruits stores proteins, enhancing seed germination survival rates.

Fruits are the mature ovary or ovaries of one or more flowers. They are found in three main anatomical categories: aggregate fruits, multiple fruits, and simple fruits.

Longitudinal section of a female flower of a squash plant (courgette), showing the ovary, ovules, pistil and petals

In some fruits, the edible portion is not derived from the ovary, but rather from the aril, such as the mangosteen or pomegranate, and the pineapple from which tissues of the flower and stem provide food.

The grains of grasses are single-seed simple fruits wherein the pericarp and seed coat are fused into one layer. This type of fruit is called a caryopsis. Examples include cereal grains, such as wheat, barley, oats and rice.

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