Aril

An aril is a specialized outgrowth from a seed that partially or completely covers the seed. This structure is often fleshy and brightly colored, which can attract animals and aid in seed dispersal. Arils are found in various plant species and are an important feature in the reproductive strategy of these plants.

Structure and Function

The aril is typically a fleshy covering that develops from the seed stalk, known as the funiculus, or from the seed coat itself. It is distinct from the fruit, which develops from the ovary of the flower. The primary function of the aril is to attract animals, such as birds and mammals, which consume the aril and subsequently disperse the seeds.

Mace of nutmeg

In some species, the aril is edible and highly valued. For example, the aril of the nutmeg seed is known as mace, a spice used in cooking. The aril of the lychee fruit is the sweet, edible part that is consumed.

Examples of Arils

Nutmeg

The nutmeg tree produces seeds that are covered by a bright red aril known as mace. This aril is removed and dried to be used as a spice. The nutmeg seed itself is also used as a spice.

Lychee

Litchi chinensis

The lychee fruit has a fleshy, sweet aril that surrounds the seed. This aril is the part of the fruit that is consumed, while the seed is discarded.

Yew

Taxus baccata

In the yew tree, the aril is a fleshy, red structure that surrounds the seed. Unlike many other arils, the yew aril is not edible due to the toxicity of the seed it encloses.

Role in Seed Dispersal

Arils play a crucial role in the dispersal of seeds. By attracting animals with their bright colors and fleshy texture, arils encourage animals to eat them. The seeds are then carried away from the parent plant and are often deposited in new locations through the animal's droppings, facilitating the spread of the plant species.

Morphogenesis and Development

The development of arils involves complex morphogenetic processes. The growth of the aril is often synchronized with the development of the seed, ensuring that the aril is mature and attractive to dispersers at the right time.

Illustration of apical constriction in epithelial cells

Apical Constriction

Apical constriction is a process that can be involved in the development of arils, as it is in many other plant and animal tissues. This process involves the contraction of cells at their apical surface, leading to changes in tissue shape and structure.

Diagram showing the cellular changes during apical constriction

Mechanisms

The mechanisms of apical constriction involve the coordinated action of actin and myosin filaments within the cells. These proteins generate contractile forces that lead to the invagination or folding of tissues.

Mechanisms of apical constriction with actin and myosin

Stages

The stages of apical constriction can be observed in various developmental processes, including the formation of arils. These stages include the initial cell shape changes, the formation of a constricted apical surface, and the eventual stabilization of the new tissue structure.

Stages of apical constriction in tissue morphogenesis

Related Pages

• Seed dispersal
• Fruit
• Nutmeg
• Lychee
• Yew