Plant kingdom

• Whittaker (1969) proposed the Five Kingdom classification: Monera, Protista, Fungi, Animalia, and Plantae
• Fungi, members of Monera and Protista with cell walls have been excluded from Plantae
• Cyanobacteria, also known as blue green algae, are not considered algae anymore
• Classification within Kingdom Plantae includes Algae, Bryophytes, Pteridophytes, Gymnosperms, and Angiosperms
• Early classification systems were based on superficial morphological characters, while natural classification systems consider internal features like ultra-structure, anatomy, embryology, and phytochemistry
• Phylogenetic classification systems are based on evolutionary relationships between organisms
• Numerical Taxonomy is based on all observable characteristics, assigning numbers and codes to each character for processing
• Cytotaxonomy uses cytological information like chromosome number, structure, and behavior
• Chemotaxonomy uses chemical constituents of plants for classification
• Algae are chlorophyll-bearing, simple, thalloid, autotrophic, and largely aquatic organisms
• Algae reproduce by vegetative, asexual, and sexual methods
• Algae are primary producers of energy-rich compounds and are important in aquatic food cycles
• Algae are divided into three main classes: Chlorophyceae, Phaeophyceae, and Rhodophyceae
• Chlorophyceae (green algae) have unicellular, colonial, or filamentous plant bodies with chlorophyll a and b
• Phaeophyceae (brown algae) are primarily found in marine habitats, storing food as complex carbohydrates
• Rhodophyceae (red algae) have red pigment r-phycoerythrin, store food as floridean starch, and reproduce vegetatively and sexually
• Bryophytes include mosses and liverworts, are amphibians of the plant kingdom, and play a role in plant succession
• Bryophytes lack true roots, stem, or leaves, and reproduce sexually through gametophytes and sporophytes
• Liverworts grow in moist, shady habitats, have thalloid plant bodies, and reproduce asexually by fragmentation or gemmae formation
• Sexual reproduction in liverworts can take place by fragmentation of thalli or by the formation of specialized structures called gemmae
• Gemmae are green, multicellular, asexual buds that develop in small receptacles called gemma cups located on the thalli
• During sexual reproduction in liverworts, male and female sex organs are produced either on the same or on different thalli
• The sporophyte in liverworts is differentiated into a foot, seta, and capsule, with spores being produced within the capsule after meiosis
• In mosses, the predominant stage of the life cycle is the gametophyte, which consists of two stages: protonema and leafy stage
• Protonema is a creeping, green, branched, and frequently filamentous stage that develops directly from a spore
• The leafy stage develops from the secondary protonema as a lateral bud, consisting of upright, slender axes bearing spirally arranged leaves
• Vegetative reproduction in mosses is by fragmentation and budding in the secondary protonema
• In sexual reproduction in mosses, the sex organs antheridia and archegonia are produced at the apex of the leafy shoots
• The sporophyte in mosses is differentiated into a foot, seta, and capsule, with spores being formed after meiosis within the capsule
• Pteridophytes include horsetails and ferns, and they are the first terrestrial plants to possess vascular tissues – xylem and phloem
• The main plant body in pteridophytes is a sporophyte, differentiated into true root, stem, and leaves with well-differentiated vascular tissues
• In pteridophytes, the leaves may be small (microphylls) as in Selaginella or large (macrophylls) as in ferns
• The sporophytes in pteridophytes bear sporangia that are subtended by leaf-like appendages called sporophylls
• Spores are produced by meiosis in spore mother cells within the sporangia, germinating to form free-living, mostly photosynthetic thalloid gametophytes called prothallus