Important Notes For Neet Plant Kingdom

Table of Contents

Classification

Algae

Bryophytes

Pteridophytes

Gymnosperms

Angiosperms

Plant Kingdom - Important Points, Summary, Revision, Highlights

Plant Kingdom

**Whittaker’s (1969) five-kingdom classification of living organisms is based on features such as complexity of cellular and body structure, mode of nutrition, etc. These five kingdoms are: Monera, Protista, Fungi, Plantae and Animalia.

##The various systems of classification that have been attempted include: -Aristotle’s classification of plants as herbs, shrubs, and trees (2000 years ago)

  1. Artificial System: Based on only a few morphological characteristics, such as the structure and number of stamens present, Linnaeus classified plants.

  2. Natural System- Based on morphological as well as anatomical characters such as cellular ultrastructure, embryology, phytochemistry, etc., Bentham and Hooker classification divided plants into two categories: Phanerogamia and Cryptogamia, based on the presence and absence of flowers and seeds.

  3. Phylogenetic System: Based on evolutionary and genetic relationships of plants, such as Whittaker, Engler, Prantl, and Eichler, etc.

Various modern taxonomic advancements include:

Numerical Taxonomy: A statistical method which gives equal importance to various different characters and utilizes computers for its implementation.

Cytotaxonomy: Based on cytological information, such as chromosome structure and number.

Chemotaxonomy: Based on Chemical Constituents

Classification of the Plant Kingdom

Plant Classification

Algae

The plant body is a thallus, which can be filamentous, colonial, unbranched, or branched and massive.

Some of the special characteristics of the plant body of various algae are:

  • Spirogyra (water-silk), Ulothrix filamentous
  • Volvox colonial
  • Unicellular Chlamydomonas, Acetabularia (largest unicellular algae), also known as the umbrella plant
  • Ectocarpus filamentous branched and epiphytes (grow on other plants)
  • Kelps giant brown algae, profusely branched and massive, may reach up to the height of 100 metres
  • Brown algae: Holdfast attaches the plant to a substratum, the stalk is known as Stipe, Frond leaf-like and carries out photosynthetic

They predominantly inhabit aquatic habitats, which can be either marine or freshwater.

Algae are autotrophic and have chlorophyll, with different shapes of chloroplast present such as:

  • Girdle shaped in Ulothrix
  • Ribbon-shaped in Spirogyra
  • Cup-shaped in Volvox and Chlamydomonas
  • Reticulate in Oedogonium
  • Disc-shaped in Caulerpa
  • Star-shaped in Zygnema

Reproduction can occur through vegetative, sexual, and asexual means.

Vegetative reproduction occurs through fragmentation

Asexual reproduction can occur via the formation of various spores, such as zoospores (which are motile) and aplanospores and akinetes (which are non-motile).

Sexual reproduction is by fusion of gametes and is of three types:

  • Fertilization
  • Parthenogenesis
  • Budding

Isogamous: Male and female gametes of organisms such as Ulothrix (which have motile or flagellated gametes) and Spirogyra (which have non-motile gametes) are similar in size.

Anisogamous: Gametes of organisms such as Eudorina and Chlamydomonas are dissimilar in size.

Oogamous: Female gamete is large and non-motile, while male gamete is small and motile, e.g. Volvox, Fucus.

Some of the special reproductive structures and processes present in different algae are:

  • Sexual reproduction by Conjugation in Spirogyra
  • Conceptacles of Sargassum, which is a flask-shaped cavity bearing male and female sex organs, antheridia and oogonia respectively
  • In Chara sex organs are multicellular and jacketed known as Globule (male antheridium) and Nucule (female archegonium)

Fucus has a diplontic life cycle, whereas Ectocarpus, Kelps and Polysiphonia have a haplo-diplontic life cycle, while the life cycle of most species is haplontic.

Phycology – the scientific study of algae

The three main classes of algae are:

  • Chlorophyceae (green algae)
  • Phaeophyceae (brown algae)
  • Rhodophyceae (red algae)
Attributes Algae

| Class | Chlorophyceae | Phaeophyceae | Rhodophyceae |

Common Name Green Algae Brown Algae Red Algae

| Habitat | Mostly Freshwater | Mostly Marine | Mostly Terrestrial |

| Type of Chlorophyll | Chlorophyll a | Chlorophyll b | Chlorophyll c | Chlorophyll d |

| Pigments | β-carotene, xanthophylls | Carotenoids, xanthophylls, fucoxanthin | r-phycoerythrin, phycocyanin, β-carotene |

| Stored Food | Carbohydrate | Mannitol, Laminarin | Floridean Starch |

| Cell Wall | Cellulose | Cellulose, Algin | Cellulose, Phosphate Esters, and Pectin |

Vegetative Reproduction Fragmentation and Spore Formation
Fragmentation Fragmentation

| Asexual Reproduction | Flagellated Zoospores | Biflagellated Zoospores (Pear-Shaped) with Unequal Laterally Attached Flagella | Non-Motile Spores |

Sexual Reproduction Isogamous, Anisogamous, or Oogamous
Isogamous Anisogamous, or Oogamous
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