Overview

Gymnosperm trees are defined as having naked seeds that are exposed to the air.  In Tamarack trees, these seeds are contained in distinct globular ovule cones pictured at the left. 

Tamarack is a monoecious tree, meaning that both pollen cones and seed cones can be found on the same tree.

Pollen is developed in the yellow-colored male cones and transferred via wind to the ovule cone where fertilization and embryo development takes place within the seeds.  The seeds then drop and with a little TLC from mother nature, a new Tamarack tree is created!

When the tree is a sporophyte, or what is commonly thought of as a ‘tree’, the sex organs are the microsporangia and the megasporangia.  The microsporangia are the pollen-producing male cones, and the megasporangia are the ovule or female cones.  Larix laricina is monoecious, meaning that both pollen cones and female cones  are found on the same tree.

The microsporangia are the pollen cones of the tree.  These are also referred to as the male cones and are typically smaller than ovule cones and yellow colored on Tamarack.  These cones contain microsporocytes that go through meiosis to produce pollen grains that contain four haploid immobile sperm cells.  These pollen grains contain two sacs to allow for easy wind transportation.  They are carried via wind to the ovule cones.

These reddish-brown scale cones are very unique to Larix laricina.

Here are some pine cones as they are on the tree.  Please note that this species is NOT Larix laricina.

    Larix laricina exhibits alteration of generations.  This means that the life cycle of Tamarack is split into two divisions including gametophyte and sporophyte generations. 

    Ovule cones are typically what are thought of as pine cones.  They are characterized by a set of scales.  Each scale contains two ovules.  Each scale is connected to the rest of the cone by a bract.  Each ovule has three components.  The first is the diploid (2n) integuments that eventually develop into the seed coat.  The second part of the ovule is the diploid (2n) megasporangium which becomes the site where pollen grain is germinated.  The third component of the ovule is the diploid (2n) megasporocyte, which is the site of archegonium development.  See the large image above for further clarification. 

    Reproduction proceeds by a process called pollination.  This is when pollen is transferred from a pollen cone to a seed cone via wind.  The seed cone secretes a liquid, to which the pollen grain sticks.  This fluid is then soaked up by the seed cone until the pollen comes in contact with one of the two ovules at the base of the scale.  When many of the ovules have been germanized, the scales on the seed cone become thick and hardy and close up. Then, the development of megagametophytes ensues. 

    The megasporocyte is initially diploid (2n).  After germination, the mother megasporocyte goes through meiosis to create four haploid (1n) megaspores.  only one of these four, called the functional megaspore (1n) will go on to produce a mature megagametophyte.  Upon maturation, a few (about 2-5) archegonium will be produced over the course of 1-2 years, each containing one egg. 

    Simultaneous with the development of the archegonium, the pollen matures and develops pollen tubes.  Pollen tubes provide the means of transportation of pollen to the egg, now fully developed inside the archegonium.  The seed is now fully formed

Much of this information has been obtained from The Seed Biology Place.  This site contains tons of good information!  Click here to proceed.

Figure 1: This diagram shows the Gymnosperm life cycle.  Pay close attention to this during the discussion about gymnosperm reproduction