Biology

Plant Kingdom

Plants are seen in various regions. They are found in deserts, rain forests, oceans, lakes and in lot of other environments. Many animals eat plants to survive. Plants also give shelter to many living organisms. They play major role in ecosystem. There are many species of plants like trees, grasses, shrubs etc. Plants take in carbon dioxide and light energy and releases oxygen. Plants are divided into several subgroups.

Characteristics of Plant Kingdom
• Plants are eukaryotic
• Plants are multicellular
• Plants are autotropic because they synthesize their food by photosynthesis using chlorophyll
• Plants have cell wall made of cellulose
• Plants have a large central vacuole that holds water
• Some plants reproduce asexually and some sexually

Classification of Plants
• Cryptogams (reproduces by spores)
 Thallophyta
 Bryophyta
 Pteridophyta
• Phanerogams (seed-bearing plants)
 Angiosperms
 Monocotyledons
 Dicotyledons
 Gymnosperms

Thallophyta
• It includes primitive plant life having simple plant body, e.g. algae, fungi.
• Algae are autotropic and have chlorophyll
• Fungi includes mould, yeast and mushrooms. Fungi do not have chlorophyll
• Fungi may develop symbiotic relationship with algae for food giving protection to algae from UV rays
• Lichens arise from symbiotic partnership of algae and fungi
• Found in moist or wet places
• They do not have vascular system required to transport water
• Mostly reserve food is starch
• They have cell wall
• Single-celled sex organs.
• Vegetative reproduction is by fragmentation. Each fragment becomes a thallus
• The asexual reproduction is through spores
• Sexual reproduction is by the fusion of gametes
• Examples are Spirogyra and Chara

Bryophyta
• Plant body is thallus-like
• Reproduction is through spores
• They need water for sexual reproduction
• They do not have roots, stems or leaves but have something similar
• They have rhizoids instead of roots. They do not absorb nutrients
• It produces gametes
• Seen in moist and shady habitats
• They do not have vascular system
• They are amphibious. Found both on land and in water
• Examples are liverworts and mosses

Pteridophyta
• They have roots, stems and leaves
• Main plant body is sporophyte
• They have vascular system having vascular tissues xylem and phloem
• They are seedless plants
• The spores germinated to form gametophytes, which have male and female sex organs
• Reproduction is through spores
• Examples are Ferns and Marsilea

Angiosperms
• Seeds are enclosed in fruits
• Well differentiated plant body
• Flowering plants
• They have vascular bundle with xylem and phloem to transport water
• In a flower the male sex organ is stamen and the female sex organ is pistil
• Pollen grains and ovules are developed in flowers
• They are divided into monocotyledons and dicotyledons
• Examples are Orchids, Eucalyptus, Rafflesia and Wolfie

Gymnosperms
• Seeds are not enclosed in fruits
• Well differentiated plant body
• They have roots, stems and leaves
• Absence of flowers
• Root is taproot
• Seeds are fertilized by pollination
• Examples are Conifers, Pine, Ginkgo and Cycus

Monocotyledons
• Contains one cotyledon (embryonic leaf)
• Have fibrous root system
• Vascular system in paired bundles
• Parallel leaf veins
• Examples are rice, wheat and banana

Dicotyledons
• Contains two cotyledons (embryonic leaves)
• Tap root system
• Vascular system is around the inside of the stem
• Netted leaf venation
• Examples are Grapes, tomatoes and Potatoes