(A) “Gymnosperms” - non-flowering seed plants

    “Gymnosperms” is an historical term used to collectively refer to the following groups of plants:
 

    The word gymnosperm (Gr: gymnos, naked + sperma, seed) refers to the principle characteristic of these groups: that they have ovules (which become seeds upon fertilization), and that the ovules are borne exposed(naked) on the surface of sporophylls. It should be noted that the gymnosperms collectively DO NOT constitute a monophyletic group. Rather, each gymnosperm lineage is an independent offshoot of the lineage ultimately leading to the flowering plants. You will study Coniferophyta, by far the most common and diverse gymnosperm lineage, as an example of the non-flowering seed plants. Conifers are the dominant species of evergreen forests in temperate or boreal areas. They are very abundant in California, and a large portion of conifer diversity is represented in the state, with species of Sequoia and Sequoiadendron (the redwoods), Pinus (pines), Cupressus (cypresses), Abies (firs), and others, found in a wide range of habitats.

   The sporophyte is the dominant stage in the conifer life cycle. The typical form of the conifer sporophyte is a tree with evergreen leaves. The gametophytes are not free living in conifers or any other gymnosperms (or flowering plants, for that matter), but rather are dependent on the sporophyte for their entire existence. In all seed plants, the spores, produced in the cones (or strobili), are not released into the environment. Instead, they are retained within sporophytic structures, the sporangia, as the gametophytes develop. The tiny male gametophyte (aka microgametophyte; contained within the pollen grain) is then carried to the female gametophyte (megagametophyte) via a process called pollination. The microgametophyte produces sperm, which fertilize the egg produced by the megagametophyte. The embryonic sporophyte develops within the megagametophyte and is packaged, together with sporophytic tissues (the integument (which forms the seed coat), and the remnants of the megasporangium (nucellus) and megagametophyte), into a stucture called the seed. The life cycle of conifers will be covered in detail in Lab 12.

   Examine the conifers and other gymnosperms on display in the lab.

• Are the leaves of all the conifers similar? How? How do conifer leaves compare with those of other gymnosperm groups (if available).
• Is the general life form comparable among conifers and between conifers and other groups? Are they always woody? Are they usually trees? Are they evergreen? Do they all produce seeds?