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The Plant Kingdom

What is a Plant?

• Definition: A plant is a multicellular eukaryote capable of producing its own food through photosynthesis.

• Key Characteristics:

  • Multicellular

  • Eukaryote

  • Autotroph (self-feeding)

  • Utilizes photosynthesis to produce glucose.

Plant Adaptations for Land

• Gametophytes: Have protective coverings for gametes.

• Cuticle: A waxy layer on leaves that prevents water loss.

• Leaves: Specialized for trapping light energy needed for photosynthesis.

• Roots: Roles include water and mineral absorption, anchoring the plant, and storing starch.

• Stems: Provide structural support and facilitate the transport of water and nutrients.

Green Algae

• Evolutionary Link: Considered the predecessor to plants due to:

  • Presence of cellulose in cell walls.

  • Containing chlorophyll for photosynthesis.

  • Storing food as starch, unlike most other organisms that store it as glycogen.

Liverworts

• First Actual Plant: All other plants evolved from liverworts.

Secondary Characteristics of Plants

• Cell Walls: Thick and composed of cellulose.

• Cuticle: A waxy, waterproof covering that aids in water retention in stems and leaves.

USES OF PLANTS BY HUMANS

• Food Sources:

  • Green Plants: Provide food for all organisms; essential producers.

  • Grains: Major food supply for humans; includes one-seeded fruits of cereal plants like rice, wheat, and maize.

    • Rice: Oryza sativa; typically grown in tropical areas.

    • Wheat: Triticum aestivum; grown in drier regions; high in proteins, carbohydrates, and B vitamins.

    • Maize: Zea mays; consumed in vast quantities.

Legume Plants

• Produce pods called legumes that open upon ripening, serving as rich protein sources.

  • Examples:

    • Soybeans – Glycine soja

    • Peanuts – Arachis hypogaea

    • Beans – Phaseolus sp

    • Green peas – Pisum sativum

Root Crops

• Fleshly storage roots typically high in starch or sugar and low in proteins and fats.

  • Examples:

    • Cassava – Manihot esculenta

    • Sweet potato – Ipomea batatas

    • Beets – Beta vulgaris

Stem Crops

• Enlarged underground stems.

  • Example:

    • Sugar Cane – Saccharum officinarum

Fruits and Leaves Usage

• Fruits: Enhance diet variety; good sources of Vitamin C.

  • Examples:

    • Banana – Musa sp

    • Coconut – Cocos nucifera

• Leaves: Low in calories but provide essential vitamins and minerals.

  • Example:

    • Cabbage – Brassica oleracea

• Forages: Plants consumed by livestock; include grass and legumes.

  • Example:

    • Alfalfa – Medicago sativa

Other Uses of Plants

Lumber

• Source of fuel and building materials.

  • Examples:

    • Pine trees – Pinus sp

    • Redwood – Sequoia sempervirens

    • Maple – Acer saccharum

Fiber Plants

• Long, slender cells used for textiles.

  • Examples:

    • Cotton – Gossypium sp (primary natural fiber)

    • Jute – Corchorus capsularis (secondary to cotton)

Beverages

• Extracted from fruits.

  • Examples:

    • Coffee – Coffea arabica

    • Tea – Thea sinensis

    • Black Pepper – Piper nigrum

Medicinal Plants

• Utilized for treating human ailments.

  • Examples:

    • Opium – Papaver somniferum (morphine source)

    • Marijuana (recreational and medicinal effects)

    • Chrysanthemum (insecticide source) - Pyrethrum.

Classification Based on Nutrition

• Autotrophic Plants: Able to manufacture their own food (e.g., most green plants).

• Heterotrophic Plants: Cannot produce food (e.g., fungi).

Classification Based on Water Requirements

• Mesophytes: Require moderate water.

• Xerophytes: Adapted to dry habitats.

• Hydrophytes: Thrive in watery environments.

• Halophytes: Require water with high salt content.

Classification Based on Habitat

• Aquatic Plants: Live in water.

• Terrestrial Plants: Live on land.

• Aerial Plants: Grown above ground, often attached to other plants.

Classification Based on Lifespan

• Annual Plants: Live for one growing season.

• Biennial Plants: Live for two years.

• Perennial Plants: Live for multiple years.

Classification Based on Appearance

• Trees: Woody with a single main stem.

• Shrubs: Woody plants with multiple branches.

• Herbs: Soft-stemmed plants.

• Vines: Climbing or twining plants.

Overview of the Plant Kingdom

• Plants are categorized into divisions; a division in plants is equivalent to a phylum in animals.

• Groups: Vascular (Tracheophytes) and non-vascular (Bryophytes).

Non-vascular Plants: Bryophytes

• Lack vascular tissue; depend on osmosis and diffusion.

• Must remain small and live in moist environments.

• Divided into three groups: liverworts, hornworts, and mosses.

Liverworts

• Considered the first plants and possibly ancestral to all plant species.

Hornworts

• Characterized by sporophytes resembling animal horns; typically found in shady, damp habitats.

Moss

• Small plants with one-cell thick leaves; grow in dense mats, utilizing rhizoids for anchoring.

Peat Moss

• Grows in acidic conditions; harvested for fuel and fertilizer.

Vascular Plants: Tracheophytes

• Possess vascular tissues for efficient transport; can grow larger and survive in diverse habitats.

• Divided into seed plants and non-seed plants.

Non-seed Plants

• Reproduction occurs through spores; require moist environments.

• Includes ferns, whisk ferns, horsetails, and club mosses.

Reproduction in Non-seed Plants

• Sperm fertilizes eggs on the prothallus, resulting in a zygote that grows into a sporophyte to produce spores.

Kinds of Non-seed Plants

• Cover bryophytes and non-vascular plants, alongside whisk ferns, club mosses, horsetails, and ferns.

Seed Plants

• Produce seeds which protect zygotes and aid in dispersal; more evolved than non-seed plants.

Types of Seed Plants

• Gymnosperms: Naked seeds usually located in cones.

• Angiosperms: Enclosed seeds found in fruits.

Gymnosperms

• Four divisions include cycads, gnetophytes, ginkgoes, and conifers.

Conifers

• Cone-bearing with needle-like leaves; adaptations minimize water loss for survival in various climates.

Angiosperms

• Flowering plants that produce seeds enclosed in fruits, with a significant role in ecosystems.

Categories of Angiosperms

• Divided based on the number of cotyledons:

  • Monocots: One seed leaf; parallel veins, multiples of three in flowers.

  • Dicots: Two seed leaves; branched veins, and flower parts in four or five.

Life Span of Flowering Plants

• Annuals: Complete life cycle in one year.

• Biennials: Two-year cycle; growth in the first year, reproduction in the second.

• Perennials: Live for multiple years, adapting to seasonal changes.