Seed Plants Angiosperms and Gymnosperms

Gymnosperms •Seed plants that produce “naked seeds”. •Seeds are not enclosed by a fruit. •The oldest type of seed plant.

Gymnosperms Many have needle-like or scale-like leaves. Pacific yew -- taxol

Cycads – Ancient plants. Four Types of gymnosperms … Cycads – Ancient plants. Look like palm trees with cones. Grow mainly in tropical or subtropical areas.

Conifers – “cone bearing”. Largest and most diverse gymnosperm group today. Most are evergreens… like firs, pines, spruces, sequoias, junipers.

Ginkgoes – also ancient. Only one species still exists. Can tolerate air pollution.

Gnetophytes Found in deserts and tropical rain forests. Are trees, shrubs, or vines. Some may live for more than 1000 years. Ephedra – ephedrine - decongestant

Gymnosperm reproduction Cones – reproductive structures Usually, both male and female cones are made by a single plant. Cones are covered by scales.

Scales on male cones produce pollen – the male gametophyte Scales on male cones produce pollen – the male gametophyte! Each scale produces thousands of pollen grains.

Scales on the female cone contain at least one ovule at the base Scales on the female cone contain at least one ovule at the base. Ovule is female gametophyte. Ovule contains egg cell. What advantage do these gametophytes have over those of nonvascular and seedless plants?

4 Steps of reproduction 1. Pollination – Wind often carries the pollen to the female cones. Pollen sticks to substance produced by ovules. 2. Fertilization -- After pollination, ovule closes and seals. p.275

3. Seed Development -- Female cones stay on tree and get bigger as seeds mature. May take up to 2 years. 4. Seed Dispersal -- Scales open when seeds mature. Wind carries them away. Few will land in places suitable for germination.