Plant Kingdom

Overview

• Plant Kingdom is part of the broad classification system of living organisms.
• Kingdom Plantae includes Algae, Bryophytes, Pteridophytes, Gymnosperms, and Angiosperms.
• Earlier classifications included fungi and some Monera and Protista as Plantae, but now they are excluded.
• Algae, Bryophytes, Pteridophytes, Gymnosperms, and Angiosperms are described in detail.

Classification Systems

• Artificial Systems: Based on superficial morphology; used by Linnaeus.
• Natural Classification: Considers natural affinities and internal features; by Bentham and Hooker.
• Phylogenetic Classification: Based on evolutionary relationships and common ancestry.
  • Includes numerical taxonomy, cytotaxonomy, and chemotaxonomy.

Algae

• Chlorophyll-bearing, simple, thalloid, autotrophic organisms.
• Mostly aquatic; found in moist environments.
• Reproduce vegetatively by fragmentation, asexually by spores, and sexually by gametes.
• Divided into: Chlorophyceae (Green), Phaeophyceae (Brown), and Rhodophyceae (Red).

Chlorophyceae (Green Algae)

• Unicellular, colonial, or filamentous.
• Grass green due to chlorophyll a and b.
• Examples: Chlamydomonas, Volvox, Ulothrix, Spirogyra, Chara.

Phaeophyceae (Brown Algae)

• Mostly marine; vary in size and form.
• Contain chlorophyll a, c, carotenoids, and xanthophylls.
• Examples: Ectocarpus, Dictyota, Laminaria, Sargassum, Fucus.

Rhodophyceae (Red Algae)

• Marine, found in warm areas.
• Predominantly red due to r-phycoerythrin.
• Examples: Polysiphonia, Porphyra, Gracilaria, Gelidium.

Bryophytes

• Mosses and liverworts; grow in moist, shaded areas.
• Called amphibians of the plant kingdom; require water for reproduction.
• Plant body is thallus-like and attached by rhizoids.
• Main plant body is the gametophyte; produces gametes.
• Divided into liverworts and mosses.

Liverworts

• Grow in moist, shady habitats.
• Thallus is dorsiventral.
• Reproduce asexually by fragmentation or gemmae.

Mosses

• Gametophyte stage predominant; consists of two stages: protonema and leafy stage.
• Reproduce vegetatively by fragmentation or budding.

Pteridophytes

• Include horsetails and ferns.
• First terrestrial plants with vascular tissues.
• Main plant body is sporophyte.
• Require water for reproduction.
• Divided into four classes: Psilopsida, Lycopsida, Sphenopsida, Pteropsida.

Gymnosperms

• Naked seeds; ovules are not enclosed by ovary walls.
• Include trees and shrubs; e.g., Sequoia.
• Heterosporous: produce microspores and megaspores.
• Examples: Cycas, Pinus, Ginkgo.

Angiosperms

• Seeds enclosed in fruits; pollen grains and ovules in flowers.
• Large group with wide range of habitats.
• Divided into dicotyledons and monocotyledons.

Summary

• Plant Kingdom includes diverse groups with varying complexity and reproduction methods.
• Algae are autotrophic and play a key role in ecosystems.
• Bryophytes have more differentiated bodies compared to algae and rely on water for reproduction.
• Pteridophytes are the first to have vascular tissues and have a dominant sporophyte phase.
• Gymnosperms have naked seeds with cones and are important in certain ecosystems.
• Angiosperms have flowers and fruits, and are crucial for human agriculture and economy.