Part 3 - Gymnosperm seed plants - Conifer (Pine)

Photos by Dr. Rob Bowker, Glendale Community College, Glendale, Arizona
(These photos are protected by copright and may not be reproduced without written permission.)

Here is a photo of male and female pine cones. The cone is the reproductive structure of a conifer.  Its form is that of a very short branch with many small, rounded,  leaf-like structures (scales) attached to a central stem. A female cone (lower half of photo) lives and grows for several years, becoming much larger than a male cone. An ovule develops on each scale of a female cone.  Inside the ovule, an egg cell is produced.  If fertilization occurs, an embryo grows inside the ovule.  The ovule hardens, becoming a seed. Eventually the scales spread, allowing the seeds to fall.  If conditions are favorable where it falls, the embryo inside the pine seed will grow into a new tree. A cluster of several male cones is shown above the female cone.

This is a close-up of the male pine cones shown above. Male cones live only a few weeks.  On each tiny scale of a male cone, a pollen sac develops, inside which pollen grains are formed.  Each pollen grain is a protective container for a sperm cell. When mature pollen is released, the male cones die and fall apart. Pollen is carried by the wind, and some of the pollen grains land between the scales of female cones, resulting in fertilization.

Male pine cone, sliced lengthwise,  viewed through microscope at low power.

Close-up of pollen sacs on male cone scales. The tiny dots all around the "X" are pollen grains.

Female pine cone, sliced lengthwise, viewed through microscope at low power.

Close-up of ovules on female cone scales. The lump of tissue marked "X" is an ovule.