Explain why seedless

Whisk ferns have been classified outside the true ferns; however, recent comparative analysis of DNA suggests that this group may have lost both vascular tissue and roots through evolution, and is actually closely related to ferns. With their large fronds, ferns are the most readily recognizable seedless vascular plants [Figure 8]. About 12, species of ferns live in environments ranging from tropics to temperate forests. Although some species survive in dry environments, most ferns are restricted to moist and shaded places.

They made their appearance in the fossil record during the Devonian period — million years ago and expanded during the Carboniferous period, — million years ago [Figure 9]. Go to this website to see an animation of the lifecycle of a fern and to test your knowledge. Landscape Designer Looking at the well-laid gardens of flowers and fountains seen in royal castles and historic houses of Europe, it is clear that the creators of those gardens knew more than art and design.

They were also familiar with the biology of the plants they chose. A landscape designer will plan traditional public spaces—such as botanical gardens, parks, college campuses, gardens, and larger developments—as well as natural areas and private gardens [Figure 10].

The restoration of natural places encroached upon by human intervention, such as wetlands, also requires the expertise of a landscape designer. Coursework in architecture and design software is also required for the completion of the degree.

The successful design of a landscape rests on an extensive knowledge of plant growth requirements, such as light and shade, moisture levels, compatibility of different species, and susceptibility to pathogens and pests. For example, mosses and ferns will thrive in a shaded area where fountains provide moisture; cacti, on the other hand, would not fare well in that environment.

The future growth of the individual plants must be taken into account to avoid crowding and competition for light and nutrients. The appearance of the space over time is also of concern.

Shapes, colors, and biology must be balanced for a well-maintained and sustainable green space. Art, architecture, and biology blend in a beautifully designed and implemented landscape. Seedless nonvascular plants are small. The dominant stage of the life cycle is the gametophyte. Without a vascular system and roots, they absorb water and nutrients through all of their exposed surfaces. There are three main groups: the liverworts, the hornworts, and the mosses. They are collectively known as bryophytes.

Vascular systems consist of xylem tissue, which transports water and minerals, and phloem tissue, which transports sugars and proteins. With the vascular system, there appeared leaves—large photosynthetic organs—and roots to absorb water from the ground. The seedless vascular plants include club mosses, which are the most primitive; whisk ferns, which lost leaves and roots by reductive evolution; horsetails, and ferns.

The bryophytes are divided into three divisions: the liverworts or Marchantiophyta, the hornworts or Anthocerotophyta, and the mosses or true Bryophyta. How did the development of a vascular system contribute to the increase in size of plants? It became possible to transport water and nutrients through the plant and not be limited by rates of diffusion.

Vascularization allowed the development of leaves, which increased efficiency of photosynthesis and provided more energy for plant growth. Skip to content Chapter Diversity of Plants. Learning Objectives By the end of this section, you will be able to: Describe the distinguishing traits of the three types of bryophytes Identify the new traits that first appear in seedless vascular plants Describe the major classes of seedless vascular plants.

Careers in Action. Why do mosses grow well in the Arctic tundra? They grow better at cold temperatures. They do not require moisture. They do not have true roots and can grow on hard surfaces. There are no herbivores in the tundra. Which is the most diverse group of seedless vascular plants? Which group are vascular plants? What are the three classes of bryophytes?

Glossary club moss the earliest group of seedless vascular plants fern a seedless vascular plant that produces large fronds; the most advanced group of seedless vascular plants hornwort a group of non-vascular plants in which stomata appear horsetail a seedless vascular plant characterized by a jointed stem liverwort the most primitive group of non-vascular plants moss a group of plants in which a primitive conductive system appears phloem the vascular tissue responsible for transport of sugars, proteins, and other solutes sporophyll a leaf modified structurally to bear sporangia strobili cone-like structures that contain the sporangia whisk fern a seedless vascular plant that lost roots and leaves by evolutionary reduction xylem the vascular tissue responsible for long-distance transport of water and nutrients.

Previous: The Plant Kingdom. Learning Objectives Evaluate the evolution of seedless vascular plants. Key Points The life cycle of seedless vascular plants alternates between a diploid sporophyte and a haploid gametophyte phase. Seedless vascular plants reproduce through unicellular, haploid spores instead of seeds; the lightweight spores allow for easy dispersion in the wind. Seedless vascular plants require water for sperm motility during reproduction and, thus, are often found in moist environments.

Key Terms gametophyte : a plant or the haploid phase in its life cycle that produces gametes by mitosis in order to produce a zygote sporophyte : a plant or the diploid phase in its life cycle that produces spores by meiosis in order to produce gametophytes tracheophyte : any plant possessing vascular tissue xylem and phloem , including ferns, conifers, and flowering plants.

Seedless Vascular Plants The vascular plants, or tracheophytes, are the dominant and most conspicuous group of land plants. Some plants capable of producing seed may have sterile pollen or other reasons that render them incapable of forming seed, and to produce seed they require pollination by another, genetically different member of that species. When planted in large orchards, they are surrounded by genetically identical copies of themselves, causing them produce parthenocarpic fruit.

Many citrus operate this way. This occurs in most seedless grapes, watermelon and other fruits. Breeders of seedless grapes capitalize off this partial development process by removing developing seeds prior to abortion and growing them into plants using tissue culture techniques. This way, both parents possess the seedless trait thereby producing a higher number of seedless offspring. Disruption of the seed development process occurs for a number of reasons.

Watermelon and banana are seedless because they have three sets of chromosomes, giving them an odd number to work with when they produce pollen and egg cells. Most organisms have an even number of chromosomes, so the resulting egg and pollen cells receive an even number of chromosomes that contain the genetic material, e. When triploids form eggs and pollen, the process produces an odd number, resulting in egg and pollen not receiving an equal chromosome compliment, therefore they lack information needed to be viable.

Pollen from triploids often appears shriveled and poorly formed. Triploid organisms occur naturally or they can be developed by crossing a diploid two sets of chromosomes with a tetraploid four sets of chromosomes to produce a triploid. In the case of watermelon, pollination needs to occur for fruit to develop and since triploid pollen does not germinate, diploid varieties are interplanted to provide viable pollen to induce fruit without complete seed development.

The white seed traces are readily visible in watermelon. Many use the word mutation or mutant in a negative context, but most changes we find desirable occurred naturally. An effort was made to develop seedless cherries. A pit is the hard, stony tissue surrounding the seed in olives, cherries, peaches, plums and apricots and is not part of the seed.

Researchers were able to develop seedless but not pitless cherries. Seedlessness may or may not change the character of the fruit.