Accessory fruit

thumb|right|A selection of accessory fruits (from left to right: [[pear, fig, and strawberry)]]

An accessory fruit is a fruit that contains tissue derived from plant parts other than the ovary. In other words, the flesh of the fruit develops not from the floral ovary, but from some adjacent tissue exterior to the carpel (for example, from receptacles or sepal). As a general rule, the accessory fruit is a combination of several floral organs, including the ovary. In contrast, true fruit forms exclusively from the ovary of the flower.

Accessory fruits are usually indehiscent, meaning that they do not split open to release seeds when they have reached maturity.

Incorporated organs

The following are examples of accessory fruits listed by the plant organ from which the accessory tissue is derived:

{| class="wikitable"

|+ Accessory Fruit Organs

! Organ !! Fruit

| Hypanthium || apple, pear, rose hip

| Involucre || pineapple

| Peduncle || cashew apple

| Perianth || anthocarps of the Nyctaginaceae

| Receptacle || fig, mulberry, pineapple, strawberry

| Calyx || eastern teaberry, rose apple

Fruit with fleshy seeds, such as pomegranate or mamoncillo, are not considered to be accessory fruits.

Examples

Apples and pears

thumb|Apple section, showing seeds plus papery expression of the ovary, surrounded by tissue formed from ripening of the hypanthium.

The part of apples and pears that is consumed is, in fact, the hypanthium. The ovary is the papery core that surrounds the apple seeds. As the hypanthium ripens it forms the edible tissues.

Roses

For roses, the hypanthium is the tissue that composes the edible part of rosehips. Roses and apples are both members of the Rosaceae family; the fact that they have similar fruit morphology is a major consideration in placing them in the same taxonomic family. It ripens into a yellow or red structure about long.

Research

Current research has proposed that a single class of genes may be responsible for regulating accessory fruit formation and ripening. A study using strawberries concluded that hormone signaling pathways involving gibberellic acid and auxin affect gene expression, and contribute to the initiation of accessory fruit development. Metabolic modifications in different developing accessory fruit tissues are due to the varied distributions of compounds such as triterpenoids and steroids.