Reproduction

 

Conifers are monoecious. This means that there are male cones and female cones on the same tree. Male cones, called staminate cones, give off pollen while their female counterparts, ovulate cones, catch the pollen blowing in the wind. This allows for the possibility of cross-fertilization which in turn increases the variation in the genes of offspring. Pollen (fertilizing haploid cell, n) and the megaspore (receiving haploid cell, n), once combined form a diploid cell. This diploid cell (2n) then grows into a zygote (baby conifer) that eventually lives in a seed.

Male strobili (cones) develop all over the tree. Female strobili on the other hand generally grow on the upper 10% of the Spruce. Most male strobili of the Blue Spruce are a brilliant shade of red when they emerge from the buds and contain hundreds of thousands of grains of pollen. Female cones turn from a pale green to a deep bright red during peak receptivity and have the potential to produce upwards of 350 to 450 seeds each! Cones mature in August and seed shed begins around mid-September and continues into the winter. Germination of seeds doesn’t take place until the spring or early summer. Optimum conditions for this germination in the habitat of the Blue Spruce are confined to open mineral soil with a good ratio of shade and direct sunlight.

The life cycle of P. pungens follows the normal life cycle of all coniferophyta dominanted by the sporophyte generation (the tree). When the sporophyte tree is mature, it produces diploid (2n) male and female cones or strobili as mentioned before. These diploid cells undergo meiosis to become haploid gametophytes. These gametophytes are the microspores of the staminate cone and the megaspores of the ovular cone. Once these haploid spores pollinate (pollen meets megaspore) they go through fertilization to create a diploid zygote. The subsequent embryo develops within a naked seed and upon receiving the proper hormonal and environmental cues, germinates and develops a diploid sporophyte, or tree.

The Colorado Spruce doesn’t start producing seeds until it is about 20, and once the tree is over 150 seed production declines.