The word gymnosperm comes from two Greek words that mean "naked-seeded," in reference to the fact that gymnosperm seeds are produced out in the open on cone scales, while the seeds of flowering plants are produced completely enclosed within fruits. In the previous lab we learnt that bryophytes and Pteridophytes of the kingdom Plantae, reproduce by spores. In gymnosperms and angiosperms (flowerng plants), however, dispersal is primarily by means of seeds, which are considerably more complex and larger than spores. In contrast to the branching patterns of most broadleaf trees, the growth of most conifers is excurrent or Monopodial (i.e., the trunk of the tree does not divide unless the terminal bud is removed). Also, with the exception of Ginkgo, most gymnosperms have evergreen leaves. Pine (Pinus Spp) is a good example of Gymnosperms. Objectives:
1. Understand the difference between the two types of leaves produced by pines, and how pine leaves differ from those of other conifers. 2. Know the life cycle of a pine tree, and be able to indicate within the life cycle where events such as meiosis, fusion of gametes, development of an embryo, and production of sperms take place. 3. Understand the differences between male (pollen) and female (seed) pine cones. 4. Know the locations and functions of a pine micropyle, integument, pollen chamber, and nucellus. 5. Know the function of the bladders or wings on pine pollen grains. 6. Be able to distinguish a pine, and a cycad from one another (if they are available for examination). Materials
1. Fresh pine branch with cluster of pollen cones (demonstration) 2. Fresh pine, and other conifer branches for examination of leaves 3. Pine seed cones with seeds on the scales
4. Conifer pollen
5. Prepared slides of longitudinal sections through a pine ovule 6. Demonstrations of specimens of Cycas and Zamia, if available
A. Conifers-Phylum Coniferophyta
Carefully examine the...
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