Strobilus

Equisetum hyemale

Equisetum sylvaticum 240405

Equisetum strobilus wm

Equisetum strobilus xs of wm showing sporangiophores

Dioon edule04

Cycas circinalis - sago palm - desc-top of trunk

Strobilus (plural: strobili) is a term used in botany to describe the structure present in many non-flowering plants where the reproductive organs are arranged. Strobili are commonly referred to as "cones" in everyday language, especially in the context of conifers like pines, where they are most easily recognized. However, strobili are also found in a variety of other plants, including certain ferns and clubmosses.

Structure and Function

A strobilus consists of a central axis with a series of modified leaves or scales arranged around it. These scales can bear sporangia (spore-producing organs) in non-seed plants or ovules and pollen in seed plants. In conifers, for example, the female strobilus develops into a woody cone that contains the seeds, while the male strobilus produces pollen. The structure of a strobilus is adapted to facilitate the efficient dispersal of spores or pollen and, in the case of seed plants, to protect and aid in the dispersal of seeds.

Types of Strobili

Strobili can be broadly classified into two types based on the kind of reproductive organs they bear:

• Sporangiate Strobili: Found in non-seed plants like ferns and horsetails, these strobili bear sporangia that produce spores. The spores are released into the air and germinate to form new plants.
• Seed Strobili: Present in seed plants, these strobili bear ovules (which develop into seeds after fertilization) and, in some cases, pollen. In conifers, separate male and female strobili are often found on the same plant.

Evolutionary Significance

Strobili represent an important evolutionary adaptation for plants in terrestrial environments. By organizing reproductive organs into compact structures, strobili facilitate more efficient reproduction and dispersal in a variety of environmental conditions. This adaptation has been crucial in the success of seed plants, in particular, allowing them to become the dominant plant group in most terrestrial ecosystems.

Examples

• In conifers, such as pines and firs, the most recognizable strobili are the woody cones that contain seeds. However, these plants also produce smaller, often less conspicuous male strobili that release pollen.
• Cycads produce large, often colorful strobili that can be either male or female, bearing either pollen or ovules, respectively.
• Among non-seed plants, clubmosses and horsetails produce spore-bearing strobili, which are usually smaller and less complex than those of seed plants.

See Also

• Cone (botany)
• Sporangium
• Seed
• Pollen
• Fern
• Conifer