Question

What are the major divisions in Plantae? Explain them.

Answer 1

Hint: Multicellular, eukaryotic organisms with the photosynthetic mode of nutrition. They are the main producer of land and water. Division of plantae is based on non- flowering with hidden reproductive organs and flowering plants with visible reproductive organs.

Complete answer:
-Kingdom Plantae is divided into two sub- kingdoms: cryptogams and phanerogamae.
-Sub kingdom- Cryptogamae (Kryptos= concealed; gamos= marriage)
-Spores producing plants that do not produce seeds and flowers.
-Reproduce sexually by gametes but sex organs are hidden.
-Include algae, bryophytes, and pteridophytes.
-Division I- Algae
-They may be small, unicellular, microscopic like Chlorella (non-motile), Chlamydomonas (motile), or branched filamentous like Chara, or multicellular unbranched filamentous like Spirogyra and Ulothrix or colonial forms like Volvox or huge macroscopic like such as seaweeds e.g. Sargassum.
-Accessory pigments like chlorophyll-b, chlorophyll- c, chlorophyll- d, carotenes, xanthophylls, and phycobilins.
-Reserve food material is starch i.e. laminarin- starch, mannitol, or Floridian- starch.
-Algae group is further divided into Chlorophyceae (green algae), Phaeophyceae (brown algae), and Rhodophyceae (red algae).
-Division II- Bryophyta
- They are known as amphibian plants as terrestrial plants that depend on external water for fertilization and completion of the life cycle.
-They show a thalloid plant body that is not differentiated into root, stem, and leaves.
-Bryophyta is further divided into hepaticopsida (liverworts), anthocerotopsida (hornworts), and Bryopsida (moss).
-Division III- Pteridophyta
-they are known as vascular cryptogams as first vascular plants and the successful terrestrial plants with true root, stem, and leaves but no flowers, fruits and seeds.
-They have a primary root that is short-lived and soon replaced by adventitious roots.
-In these plants, the xylem consists of only tracheids and phloem sieve cells only.
-Pteridophyta is further divided as psilopsida, lycopsids, sphenopsida ad pteropsida.

-Sub kingdom- Phanerogamae (Phaneros= visible)
-Seed producing plants which have special reproductive structures that are visible
-They are commonly called seed plants.
-Include gymnosperms and angiosperms.
-Division II- Gymnospermae
-These plants have naked seeds with simpler members of phanerogams without ovaries.
-These plants are vascular plants as they have xylem with tracheids and phloem with sieve cells.
-They show heteromorphic alternation of generation.
I-Sporophyte is diploid, dominant, autotrophic and independent
II- gametophyte is haploid, recessive, and dependent. The gametophyte is very much reduced.
-These plants have a well-developed tap root system.
-Division I- Angiosperms
-These divisions have most advanced plants having flowering plants, seeds are enclosed within the ovary inside the fruit.
-These plants show vessels and phloem have companion cells and sieve tubes.
-Angiosperms show double fertilization where the first male gamete fuses with the egg cell to form second male gamete fuses with the secondary nucleus to form endosperm.

Additional Information:
-Species of Sphagnum, a moss, provide peat that has long been used as fuel, and because of their capacity to hold water as packing material for transport of living materials.
-Plants are heterosporous which means plant produces two types of spores different in size and sex,
Microspores- Microsporangia- Microsporophylls (stamens)
Megaspores- Megasporangia- Megasporophylls (carpels)
-Plants are homosporous which means plant producing spores of one kind that are not differentiated.

Note: -The sunflower family contains the largest flowering plant families containing the greatest number of species up to 24,000 approx.
-Pandora, a single male Quaking Aspen (Populus tremuloides) is known as the largest plant in the world.
-Rafflesia arnoldii flower is the world’s largest bloom.