Angiosperms and Gymnosperms

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PRACTICAL 6
Seed Plants (Gymnosperms and Angiosperms)

OBJECTIVES:
1. To describe the features of seed plant life cycle and the concept of the dominant generation. 2. To describe the life histories and related reproductive structures of gymnosperms and angiosperms. 3. To summarize the features that distinguish gymnosperms and angiosperms. 4. To discuss the advantages of seed plants to dominate land and their evolutionary adaptations on land.

EXPERIMENT 1: Gymnosperms

INTRODUCTION:
Gymnosperms (720 species in 65 genera) are ancient seed plants that include ginkgos (Division Ginkgophyta), cycads (Division Cycadophyta), conifers (Division Coniferophyta), and gnetophytes (Division Gnetophyta). The term gymnosperm derives from the Greek wood roots gymnos, meaning “naked”, and sperma, meaning “seed”. They are naked-seeded plants meaning that the ovule, which becomes a seed, is exposed on the sporophyte at pollination. Mature seed are not enclosed in a fruit as are those of flowering plants. Gymnosperms are best known for their characteristic cones, called strobili. These strobili display sporangia and their subsequently developing ovules and pollens. Gymnosperms do not require water for sperm to swim to reach the egg as do seedless plants. Instead, immense amount of windblown pollen are produced. Most gymnosperm cones, including the familiar pine cone, are complex whorls of leaflike, woody scales around a central axis. The smallest cones include those of the junipers (Juniperus) which have flesh scales fused into a structure resembling a berry. The larger cones may weigh 45 kg and are produced by cycads. In most gymnosperm species, the female megastrobilus is larger and distinctive from the male microstrobilus.

MATERIALS:
1. Living or preserved specimens of
* Ginkgo (Ginkgo biloba)
* Cycad (Cycad sp.)
* Pine (Pinus sp.)
2. Prepared slide of gymnosperms
3. Compound microscope
4. Dissecting microscope
5. Slide and coverslip
6. Forceps
7. Distilled water

PROCEDURE:
A ginkgo:
1. A prepared slide of male strobilus of Ginkgo biloba is examined. The microsporophyll, microsporangium, and strobilus axis are identified. 2. A prepared slide of female strobilus of Ginkgo biloba is examined. The megasporophyll, megasporangium, and strobilus axis are identified. A cycad:

1. A female cycad is examined. The leaves, megasporophylls, megasporangia and developing seed are identified. 2. The pollen cone bears on male cycad. Pollinated cone is examined and microsporophyll, microsporangia, and pollen grains are identified. A pine:

1. A male cone and female cone of Pinus sp. are obtained. 2. A prepared slide of longitudinal section of female cone is examined. The megasporophyll, megasporangia, and ovule are looked. 3. A prepared slide of longitudinal section of male cone is examined. The microsporophyll, microsporangia, and pollen grains are looked. 4. Fertilization occurs after the pollen tube penetrates the megasporangium and allows sperm to enter the archegonium and fuses with the egg. The zygote will form after fertilization. A prepared slide of the developing embryo of Pinus sp. is examined. 5. Mature seed cone is obtained. The seed with wing attached to the ovuliferous scale is found. 6. The anatomy of pine leaf one needle is examined. The following: epidermis, stoma, photosynthetic mesophyll, endodermis, phloem, xylem, and resin duct are identified.

RESULTS

Cross section of Ginkgo Biloba

Cross section of Cycad

Cross section of female pine

Cross section of male pine

EXPERIMENT 2: Angiosperms

INTRODUCTION:
Angiosperms are the most abundant, diverse, and widespread of all land plants. They are successful because they are structurally diverse, have efficient vascular systems, share a variety of mutualisms (especially with insects and fungi), and have short generation times. Flowering plants are important to human because our...
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