Plant Diversity


How long does it take to produce a mature pinecone?

From the time young cones appear on the tree, it takes nearly three years for them to mature. The spores of a pine tree are located on scalelike features (sporophylls) that are densely packed in structures called cones. Conifers, like all seed plants, are heterosporous, meaning that male and female gametophytes develop from spores produced by separate cones. Small pollen cones produce microspores that develop into the male gametophytes or pollen grains, and larger cones make megaspores that develop into female gametophytes. Each tree usually has both types of cones. This three-year process culminates in the production of male and female gametophytes, brought together through pollination, and the formation of mature seeds from the fertilized ovules. The scales of ovulate cones then separate, and the seeds are scattered by wind or wildlife. A seed that lands on a habitable place germinates, its embryo emerging as a pine seedling. (For more about gametophytes, see this chapter.)


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