A silique is a dry fruit found on certain plants, recognized by its unique structure and how it opens to release seeds. Unlike fleshy fruits, siliques are pods that split apart when mature. This characteristic is important for how these plants reproduce and spread their seeds.
Key Features of a Silique
A silique develops from a flower’s ovary, formed from two fused carpels. As the fruit matures, it dries and undergoes dehiscence, splitting open to release its seeds. This splitting typically occurs along two seams, allowing the outer walls, known as valves, to separate.
A defining feature of the silique is the persistent central partition, or septum, that remains after the valves detach. Seeds are typically attached to this septum. The replum, a frame-like structure, connects the two valves and supports the septum. It also serves as a main vascular structure, providing nutrients to the developing seeds.
Siliques are generally elongated, with their length being at least three times greater than their width. This ratio helps distinguish a silique from a silicle, a shorter, broader version of the same fruit type. The coordinated drying and lignification (hardening) of specific cell layers within the silique create tension, leading to the valves separating from the replum.
Plants with Siliques
Siliques are a characteristic fruit type of the Brassicaceae family, commonly known as the mustard or cabbage family. Many cultivated plants belong to this family. For instance, various types of mustard plants, such as white mustard, produce siliques.
Many common vegetables also belong to this family and produce siliques if allowed to go to seed. These include cabbage, broccoli, cauliflower, Brussels sprouts, kale, kohlrabi, and turnip, all cultivated forms of Brassica oleracea. While the edible parts of these plants are usually harvested before the siliques fully develop, the presence of this fruit type is a botanical indicator of their family. Radish and arugula are other familiar examples that develop siliques.
Canola, or rapeseed, is another significant crop from the Brassicaceae family known for its siliques, which are harvested for oil production. Silique dehiscence is vital for seed dispersal in wild plants, but in agriculture, this natural shattering can lead to significant crop yield losses, prompting research into developing shatter-resistant varieties. Shepherd’s purse (Capsella bursa-pastoris), a common weed, is a classic example of a plant with silicles, the shorter, broader version of a silique.