Chapter 3: Plant Kingdom

Gymnosperms are vascular seed-producing plants in which the ovules are not enclosed within an ovary. Their seeds are therefore described as naked seeds.

Important characteristics

• The sporophyte is the dominant plant body.
• Plants are usually woody, perennial and evergreen, although exceptions occur.
• Roots, stems and leaves are well differentiated.
• Many gymnosperms possess a taproot system.
• In some genera, roots form specialised associations, such as coralloid roots in Cycas.
• Leaves may be needle-like or scale-like, reducing water loss in many species.
• Reproductive structures are commonly organised into cones or strobili.
• Ovules are not enclosed in an ovary, and fruits are not formed.

Reproduction

• Gymnosperms are heterosporous.
• Microspores develop into male gametophytes, commonly represented by pollen grains.
• Megaspores develop within ovules and give rise to female gametophytes.
• Pollination transfers pollen to the ovule or its vicinity, depending on the group.
• Fertilisation leads to embryo development within the seed.

Examples and distinctive features

• Cycas: Has pinnate leaves and coralloid roots containing cyanobacteria. Male and female reproductive structures occur on separate plants.
• Pinus: Has needle-like leaves, commonly forms male and female cones, and often develops mycorrhizal associations.
• Gnetum: Has certain features that resemble those of angiosperms, such as broad leaves in some species.

Economic importance

• Wood from some gymnosperms is used in construction and paper production.
• Resins and other products are obtained from certain species.
• Several gymnosperms are used as ornamental plants.