Gymnosperms: naked seeds

Gymnosperm means naked seed (gymnos: naked, sperma: seed). The ovules have no ovary wall around them and stay exposed before and after fertilisation, so the seeds that follow are uncovered.

Gymnosperms are medium or tall trees and shrubs. The giant redwood Sequoia is among the tallest tree species.

Roots are usually tap roots. In Pinus the roots associate with fungi as mycorrhiza. In Cycas, small specialised coralloid roots house nitrogen-fixing cyanobacteria.

Stems may be unbranched (Cycas) or branched (Pinus, Cedrus). Leaves may be simple or compound; the pinnate leaves of Cycas last a few years.

Leaves are built to withstand extremes of temperature, humidity and wind. Conifer needles cut the surface area, and a thick cuticle and sunken stomata cut water loss further.