Biology Today - May 2018

• The Kingdom Plantae includes eukaryotic, photosynthetic organisms. According to traditional systems of classification, the

Kingdom Plantae is divided into two subkingdoms : Cryptogamae and Phanerogamae. Cryptogamae is further divided into algae,

bryophyta and pteridophyta, while phanerogamae is further divided into gymnospermae and angiospermae.

Algae

• Plant body is undifferentiated
  and is known as thallus.


• It may range from microscopic
  unicellular to macroscopic
  multicellular forms.


• The plants are non-vascular
  and chlorophyllous.

Bryophyta

• Represent group of
  plants growing in
  amphibious habitat.


• They are simpler and
  smaller embryophytes.

Pteridophyta

• Referred as first land
  plants or vascular
  cryptogams as they
  possess xylem and
  phloem.

Gymnospermae

• Naked seed bearing
  plants.


• Flowers are absent.


• Vascular tissue are
  present, xylem vessels
  are absent.

Angiospermae

• Plants bear covered seeds
  and fruits. Most evolved
  group of plant kingdom.


• Vascular tissue contains
  xylem vessels.


• Double fertilisation occurs.

Kingdom Plantae

Cryptogamae

• Plants called cryptogams do not bear conspicuous reproductive
  structures like seeds i.e., seedless plants.


• Plant body is not well organised and do not bear flowers, fruits and seeds.


• The reproductive structures or sex organs are invisible.

Phanerogamae

• Phanerogams are flowering or seed plants.


• The plant body is differentiated into root, stem and leaves.


• They bear visible reproductive structures like cones and flowers.


• There are vascular plant.

ALGAE

• Algae are chlorophyllous thallophytes characterised by the absence of embryo stage and presence of non-jacketed gametangia.


• These are usually aquatic, either marine or fresh water, a few algae occur in moist terrestrial habitat.


• Algae are covered by mucilage which protects them from epiphytic growth and decaying effect of water and also prevents

desiccation.

• Vascular tissues and mechanical tissues are absent.


• Algae mainly contain chlorophyll a, carotenes and xanthophylls.


• Algae are usually classified on the basis of their pigments, flagellation and storage products.


• According to Whittaker (1969), algae are of three types : red algae (Rhodophyta), brown algae (Phaeophyta) and green algae

(Chlorophyta).

• Vegetative, asexual and sexual modes of reproduction are present.


• Vegetative reproduction may take place by fragmentation (e.g., Ulothrix, Oedogonium), fission (e.g.,Chlamydomonas), hormogonia

(e.g., Oscillatoria), tubers (e.g., Chara), budding (e.g., Polysiphonia), etc.

• Asexual reproduction takes place by flagellated zoospores (e.g., Ulothrix, Oedogonium); non-motile, thin walled aplanospore

(e.g., Chlorella, Microspora) and non-motile, thick walled hypnospores (e.g., Vaucheria, Chlamydomonas nivalis, thick walled

akinetes (e.g., Cladophora), palmella stage (e.g., Chlamydomonas).

• Sexual reproduction involves isogamy, anisogamy and oogamy in different groups.


• Life cycle may be haplontic, diplontic or diplohaplontic.

Plant Kingdom