Kingdom Plantae – The Division Bryophyta

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Kingdom Plantae – The Division Bryophyta

For the sake of convenience organisms included in Plantae can be divided into two broad classifications viz. nonvascular (Bryophyta) and vascular (Tracheophyta) plants.

Although this grouping is not according to any specific system of classification however it does reflect resemblances and dissimilarities amongst numerous groups of plants.

Each classification (division) is divided into Subdivisions, Classes, Subclasses, and other taxonomic ranks.

In this article, you will learn about the division Bryophyta.

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Overview

The very first plants to colonize land were the bryophytes. They are typically thought to have developed from green algae. The Bryophytes are poorly adapted to reside on land and are generally confined to damp shady locations. These plants are devoid of specialized conducting (xylem and phloem) and strengthening tissues.

Just the process of diffusion and osmosis assists in the transport of water and minerals as well as in the transport of prepared food and other substances. The plant body is with a proper cuticle or has a very thin one. The water is taken in by the basic surface of the plant. The bryophytes are stated to be the amphibians of the plant world because they cannot live far from water. They need water for reproduction.

Characteristics of Bryophyta
  • The bryophytes are non-vascular flowerless plants.
  • These plants show a regular alternation of heteromorphic (morphologically different) generations.
  • They have a dominant independent free-living gametophyte. This might be thalloid as in lots of liverworts or is differentiated into structures resembling to stem, leaves and absorbing and anchoring organs, rhizoids, as in mosses and some liverworts.
  • The gametophyte produces a sporophyte, which is a less conspicuous generation, partially or absolutely reliant upon the gametophyte for its nutrition.
  • The sporophyte normally includes the foot, seta, and capsule. The sporophyte is diploid (2n) which produces in sporangia one kind of haploid spores (i.e., it is homosporous) by meiosis.
  • The spores sprout and trigger gametophyte which is likewise haploid. Multicellular male and female sex organs i.e., antheridia and archegonia respectively, are born upon gametophyte either on very same or different plants. These sex organs are multicellular and protected by a sterilized covering of cells.

Gametes are produced by mitosis. Male gametes produced within antheridia are called antherozoids; antherozoids are motile and constantly produced in a great number. Female gametes formed within archegonia are called eggs. A single egg is formed in each archegonium.

Fertilization and Development

Fertilization takes place in water. Antherozoids (n) are drawn in towards archegonia (n) chemotactically. A single antherozoid fuse with an egg (n) thus accomplishing fertilization which leads to the development of the diploid zygote (2n). The zygote is kept within the female sex organ (archegonium) for a long time. After a resting period, the zygote establishes through mitotic divisions into a diploid embryo. The embryo ultimately becomes a sporophyte which is likewise diploid.

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The entire development of sporophyte thus takes place within the gametophyte plant body. Even when the sporophyte is completely developed it remains attached to the gametophyte for nourishment and protection because it does not consist of chloroplasts and is unable to perform photosynthesis.

Alternation of Generation

There is an alternation of generations in the life process of bryophytes i.e., multicellular haploid gametophytic (gamete producing) generation alternates with the multicellular diploid sporophytic (spore-producing) generation. It is a really crucial phenomenon, which supplies constant genetic variations and choice for the best genetic makeup for survival and adaptation in the changing environment(s).

Alternation-of-Genera

Adaptation to Terrestrial Habitat

In general, bryophytes established the following adaptive characters for the terrestrial environment:

  1. The formation of a compact multicellular plant body helped in the conservation of water by reducing cell area exposed to dryland conditions. The presence of a cuticle additionally decreases the loss of water by evaporation.
  2. Development of photosynthetic tissues into special chambers for the absorption of carbon dioxide without losing much water and direct exposure to light.
  3. Development of unique structures like rhizoids for the absorption of water and anchorage.
  4. Heterogamy (production of two types of gametes) is evolved, forming nonmotile egg containing stored food and motile sperms.
  5. Gametes are produced and safeguarded by the special multicellular organs (antheridia and archegonia).
  6. The multicellular embryo is formed which is maintained and protected inside the female reproductive body throughout its development.
  7. Alternation of spore-producing generation (sporophyte) with gamete producing generation (gametophyte) enabled the plant to produce and evaluate the very best genetic recombinations for adapting to the versatile terrestrial conditions.

MCQs with Answers: Kingdom Plantae – The Division Bryophyta

  1. What is the primary division of Plantae discussed in the tutorial?
    • a) Tracheophyta
    • b) Bryophyta
    • c) Angiosperms
    • d) Gymnosperms
    • Answer: b
  2. Where are bryophytes typically confined due to their poor adaptation to land?
    • a) Arid regions
    • b) Sandy deserts
    • c) Moist shady areas
    • d) Mountainous terrain
    • Answer: c
  3. What is the main role of diffusion and osmosis in bryophytes?
    • a) Reproduction
    • b) Water and mineral transport
    • c) Photosynthesis
    • d) Chlorophyll production
    • Answer: b
  4. Which generation is dominant in bryophytes?
    • a) Gametophyte
    • b) Sporophyte
    • c) Haploid
    • d) Diploid
    • Answer: a
  5. What structures are present on the gametophyte that resemble stem, leaves, and rhizoids?
    • a) Thalloid
    • b) Xylem and phloem
    • c) Sporophyte
    • d) Seta
    • Answer: a
  6. In bryophytes, where does fertilization take place?
    • a) In the air
    • b) In the soil
    • c) In water
    • d) Inside archegonia
    • Answer: c
  7. What is the main characteristic of the sporophyte in bryophytes?
    • a) Chloroplasts for photosynthesis
    • b) Diploid and attached to gametophyte
    • c) Independent nutrition
    • d) Haploid spores
    • Answer: b
  8. What is the key phenomenon in the life cycle of bryophytes, providing genetic variations?
    • a) Meiosis
    • b) Alternation of generation
    • c) Mitosis
    • d) Homospory
    • Answer: b
  9. What does the alternation of generations involve in bryophytes?
    • a) Change in size of the plant body
    • b) Shift from diploid to haploid generations
    • c) Successive dominance of gametophyte
    • d) Multicellular embryo formation
    • Answer: b
  10. How do bryophytes conserve water in terrestrial environments?
    • a) Through extensive root systems
    • b) By reducing cell area exposed to dryland
    • c) Absorption through leaves
    • d) Utilizing specialized conducting tissues
    • Answer: b
  11. What is the main reason the sporophyte remains attached to the gametophyte?
    • a) Photosynthesis
    • b) Lack of chloroplasts
    • c) Protection and nourishment
    • d) Evolutionary adaptation
    • Answer: c
  12. What is the significance of heterogamy in bryophytes?
    • a) Chlorophyll production
    • b) Nonmotile egg production
    • c) Water absorption
    • d) Continuous genetic variations
    • Answer: d
  13. What structures are developed for the absorption of water and anchorage in bryophytes?
    • a) Xylem and phloem
    • b) Rhizoids
    • c) Seta
    • d) Antheridia and archegonia
    • Answer: b
  14. What is the primary role of rhizoids in bryophytes?
    • a) Photosynthesis
    • b) Absorption of water and anchorage
    • c) Spore production
    • d) Fertilization
    • Answer: b
  15. In which generation does meiosis occur in bryophytes?
    • a) Gametophyte
    • b) Sporophyte
    • c) Both
    • d) Neither
    • Answer: b
  16. What is the primary habitat adaptation feature of bryophytes?
    • a) Extensive root systems
    • b) Development of specialized conducting tissues
    • c) Formation of multicellular embryos
    • d) Compact multicellular plant body
    • Answer: d
  17. What is the function of the cuticle in bryophytes?
    • a) Absorption of water
    • b) Protection against UV radiation
    • c) Reduction of water loss by evaporation
    • d) Aiding in photosynthesis
    • Answer: c
  18. Why are bryophytes often referred to as amphibians of the plant world?
    • a) They live both in water and on land
    • b) They have both male and female reproductive organs
    • c) They exhibit a unique life cycle
    • d) They lack chloroplasts
    • Answer: a
  19. What does the adaptation to a terrestrial habitat involve in bryophytes?
    • a) Specialized conducting tissues
    • b) Absorption of UV radiation
    • c) Conservation of water and reduction of evaporation
    • d) Increase in cell surface area
    • Answer: c
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FAQs – Kingdom Plantae – The Division Bryophyta

  1. What is the significance of dividing organisms in Plantae into nonvascular (Bryophyta) and vascular (Tracheophyta) plants?
    • Answer: This division helps in understanding the similarities and differences among various plant groups, although it does not strictly follow a specific classification system.
  2. Which were the first plants to colonize land, and why are they called amphibians of the plant world?
    • Answer: Bryophytes were the first plants to colonize land. They are called amphibians of the plant world because they cannot live far from water and require water for reproduction.
  3. What are the main characteristics of Bryophyta?
    • Answer: Bryophytes are non-vascular flowerless plants, exhibit alternation of heteromorphic generations, have a dominant independent free-living gametophyte, and produce a less conspicuous sporophyte generation.
  4. What structures are present on the gametophyte in Bryophyta, and how is the sporophyte nourished?
    • Answer: The gametophyte may be thalloid or differentiated into stem-like structures, leaves, and rhizoids. The sporophyte is nourished by the gametophyte as it lacks chloroplasts and cannot perform photosynthesis.
  5. Where does fertilization take place in Bryophyta, and what is the role of antherozoids and archegonia?
    • Answer: Fertilization takes place in water. Antherozoids (male gametes) are attracted chemotactically to archegonia (female gametes). Antherozoids fuse with eggs inside archegonia, leading to diploid zygote formation.
  6. What is the alternation of generations in Bryophyta, and why is it significant?
    • Answer: Alternation of generations involves the alternation between multicellular haploid gametophytic and multicellular diploid sporophytic generations. It provides genetic variations for adaptation in changing environments.
  7. How do Bryophytes adapt to a terrestrial habitat?
    • Answer: Bryophytes adapt to a terrestrial habitat by forming compact multicellular plant bodies, developing special chambers for photosynthesis, creating structures like rhizoids for water absorption and anchorage, and evolving heterogamy for diverse genetic combinations.
  8. Why does the sporophyte remain attached to the gametophyte in Bryophyta?
    • Answer: The sporophyte remains attached to the gametophyte for nourishment and protection because it lacks chloroplasts and is unable to perform photosynthesis.
  9. What is the role of the cuticle in Bryophytes, and why is it important for water conservation?
    • Answer: The cuticle helps reduce water loss by evaporation, contributing to the conservation of water in Bryophytes.
  10. How does Bryophyta ensure the best genetic recombinations for adapting to terrestrial conditions?
    • Answer: Alternation of spore-producing generation (sporophyte) with gamete-producing generation (gametophyte) allows Bryophytes to produce and evaluate the best genetic recombinations for adapting to versatile terrestrial conditions.
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Summary: Kingdom Plantae

The tutorial delves into the fascinating world of Bryophyta, a division of nonvascular plants within the Kingdom Plantae. Here’s a brief overview of the key points covered:

  1. Introduction to Bryophyta:
    • Bryophyta is part of the Plantae kingdom, categorized into nonvascular plants (Bryophyta) and vascular plants (Tracheophyta). The first plants to colonize land were the bryophytes, believed to have evolved from green algae.
  2. Characteristics of Bryophyta:
    • Bryophytes are non-vascular, flowerless plants exhibiting alternation of heteromorphic generations. They feature a dominant, independent, free-living gametophyte, which may be thalloid or differentiated into structures like stems, leaves, and rhizoids. The sporophyte generation relies on the gametophyte for nutrition.
  3. Fertilization and Development:
    • Fertilization in bryophytes occurs in water, involving chemotactic attraction of antherozoids to archegonia. The diploid zygote develops into a sporophyte within the female sex organ, remaining attached to the gametophyte for nourishment and protection due to its inability to perform photosynthesis.
  4. Alternation of Generation:
    • Bryophytes undergo alternation of generations, involving the shift between multicellular haploid gametophytic and multicellular diploid sporophytic phases. This phenomenon ensures continuous genetic variations, fostering adaptation in changing environments.
  5. Adaptation to Terrestrial Habitat:
    • Bryophytes have evolved adaptive features for terrestrial life, including the formation of compact multicellular bodies for water conservation, development of specialized chambers for photosynthesis, unique structures like rhizoids for water absorption, and the evolution of heterogamy for diverse genetic combinations.

In conclusion, the study of Bryophyta provides insights into the unique reproductive and adaptive strategies of nonvascular plants, offering a glimpse into the early stages of plant evolution and their ability to thrive in terrestrial environments.

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