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An in-depth exploration of the unique features of ferns, focusing on their cellular organization, growth patterns, and reproductive processes. Ferns, belonging to the phylum tracheophyta and class filicineae, are vascular plants that reproduce via spores. They have specialized tissues called rhizomes, which are horizontal stems that grow under the soil and produce new roots and leaves each season. Ferns have true roots, large fronds, and specialized structures called sori that contain sporangia, which produce spores. The document also discusses the differences between the sporophyte and gametophyte generations, and the process of fertilization.
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Typology: Schemes and Mind Maps
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Special Characteristics of Ferns Pre-Lab Discussion Ferns belong to a group of plants that are "true" land plants. These plants have specialized tissues called vascular (conducting or "plumbing") tissues that transport water and the products of photosynthesis throughout the plant. For this reason, these plants are called vascular plants. Vascular plants can grow much larger than plants without vascular tissues. When comparing cellular organization, ferns lie between mosses and more complex vascular plants, such as trees. Ferns belong to the Phylum Tracheophyta and grouped together into the Class Filicineae because they produce spores instead of seeds. Plants reproducing using seeds are grouped into the Classes Gymnospermae and Angiospermae. These two classes are distinguished from one another on the basis of where the seeds are found on the plant (ie. cones vs. flowers). Most ferns do not have sturdy, erect stems. Instead a thick stem runs horizontally under the soil. It is usually covered with scales. Underground stems of this type are called rhizomes. Inside the rhizomes are vascular tissues that carry water and food through the plant. Fern rhizomes live from year to year. They gradually grow outward through the soil and produce numerous roots and leaves each season. Because of the creeping rhizomes, ferns are often found in large clumps. Unlike mosses, ferns do have true roots. Clusters of roots develop from the rhizome. They anchor the fem in place and absorb water from the soil. The leaves of ferns are usually large and are called fronds. The fronds die in the winter and a new set develops from the rhizome each spring. A frond consists of 3 parts: a blade , a rachis , and a stipe. The large expanded part of the fern is the blade. The midrib that supports the blade is the rachis. The stipe is the stalk that attaches the rachis to the rhizome. The blade is usually divided into many leaflets that are arranged in 2 rows along the sides of the rachis. As new fronds develop in the spring they unroll from tightly coiled buds produced by the rhizome. Because they look like the curved end of a violin, these young fronds are called fiddleheads. The fiddleheads of some (not all!) ferns are edible. When the fern is mature, raised brown dots appear on the lower surfaces of the blades. These "dots" are called sori (singular = sorus ). Each sorus contains a cluster of sporangia (spore cases). These sporangia produce thousands of dust-like spores. Sporangia are very sensitive to the amount of moisture in the air. Under certain conditions the sporangia tear open and spores are shot out in a manner similar to that of sling-shot. If a spore lands in a warm damp place, it germinates and develops into the first of cells of the gametophyte generation. A fern gametophyte starts as a short filament of cells with a few rhizoids to anchor it. It then widens into a flat sheet of cells called a prothallus (pro = early; thallus a plant body). The prothallus is heart- shaped and smaller that a dime in diameter! It has rhizoids, but no root , stems or leaves. Most people have never seen fern prothalli, because they are so tiny and short-lived. The function of the prothallus is to produce gametes. Both the male and female sex organs develop on the under surface of the prothallus. The male sex organs, antheridia are found near the apex or point of the heart-shaped prothallus, among the rhizoids. They are dome-shaped and produce the male gametes which are spirally-coiled sperm cells. The sperm have many flagella to help them swim to the site of the female gametes. The female sex organs, archegonia are located near the notched end of the heart-shaped prothallus. They are shaped like a flower vase and contain one female gamete or egg cell.
Because the sperm swim, water is required for fertilization! The sperm swim to the nearby female archegonium, enter, and fuse with the egg. Only a single sperm fertilizes each egg. The resulting zygote is the first cell of the sporophyte generation. While still inside the archegonium, the zygote begins to grow into the sporophyte. At fist ft is parasitic on the prothallus, absorbing its food and water from it. In a few days the sporophyte produces a leaf, root, and stem and contains chlorophyll. It can now produce its own food and is no longer dependent on the gametophyte. As the sporophyte develops, the tiny prothallus withers and dies. In this investigation, you will observe some of the characteristics of ferns. You will also examine how ferns reproduce. Procedure : Part A: Characteristics of the Sporophyte Fern