East Lansing Sexual Education: Get Smart about Conifers

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Monday, May 11, 2015, 12:18 am
By: 
Aron Sousa, MD

Above: Photo of a Norway Spruce in East Lansing, showing many small, tan male cones (staminate cones) as well as a single, large, pink, and receptive female cone called an ovulate cone

Today we bring you a very special ELi on Earth . . .

Conifers are a division (Pinophyta) of the plant kingdom to which pines, spruces, furs and redwoods all belong. East Lansing has been inundated with conifer sex in the last couple of weeks. All over town, the male cones of conifers have been releasing their yellow gametes to be carried by the wind to female cones. Sometimes the wind carries the male gametes (called pollen) to female cones on a neighboring tree, sometimes the pollen lands on the female cones of the same tree, and sometimes the wind spills the pollen into my house, as you see below in a photo of the floor of my solarium. That’s just how conifers get it on. (Article continues after image.)

The male cone of conifers is called a staminate cone and there are many of these on most mature conifers. In the picture at the top of this article, the male staminate cones are the small tan structures scattered about the branch. These staminate cones produce and release pollen, which are the male reproductive cells of the conifer. Like sperm in animals (including humans), pollen has half of the chromosomes of a regular cell from the species.

The female cones, ovulate cones, turn from green to pink as they become receptive to pollen. In the picture above, of the spruce male and female cones, the female cone is the single, large, pink structure in the middle of the image. The ovulate cones hold the female gametes of the tree, called “megaspores,” which, like the male, have half the chromosomes of a regular plant cell. When receptive to fertilization, the female ovulate cones open slightly and the male pollen can enter the ovulate cone, fuse with megaspore, and form a zygote, which has the full chromosomes of the species, just like in animals and flowering plants.

The ovulate cones will mature into pine cones and the zygotes will mature into seeds between the scales of the cone. (The scales on the redwood cone, shown below, are in the same spiral pattern as on the spruce ovulate cones, shown above.) Pine cones, scientifically referred to as a strobilus, can take one to three years to develop. Once mature, pine cones open to release their seeds.

Below: Mature Giant Sequoia cones that have opened to release seeds

 

Below: redwood seeds from a Giant Sequoia

 

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