How are cycads different from conifers?

Cycads and conifers are both gymnosperms, but they exhibit significant differences in their anatomy, growth, and reproductive strategies.

Structural and Growth Differences

• Stem Development: A primary distinction lies in stem growth. Cycads possess a primary thickening meristem (PTM), which results in a pachycaulous stem—one that is roughly as thick at the crown as at the base, contributing to their palmlike appearance. In contrast, conifers lack a PTM, and their stems are typically narrower at the apex than at the base.1
• Foliage: Conifers are characterized by needle-like or scale-like leaves. Cycads are distinguished by their compound leaves.23
• Vascular Anatomy: Cycad stems contain girdling leaf traces, a feature not found in coniferophytes.1

Reproductive Differences

• Sexuality: Cycads are universally dioecious, meaning male and female reproductive structures are borne on separate individual plants. Most conifers are monoecious, bearing both male and female cones on the same tree.45
• Cones: Conifers typically combine simple pollen cones with compound seed cones. Cycads generally produce simple cones, though the genus Cycas is unique in that its ovules develop on leaflike megasporophylls rather than in a true cone.243
• Pollen and Sperm: Conifer pollen is often characterized by air-filled "wings" or bladders. Cycad sperm are multiflagellate and motile, whereas conifer sperm lack flagella.42