Plant Structure and Function

Plant Structure

• Plants are multicellular eukaryotes with cell walls made of cellulose and are autotrophic, producing their own food.

Roots

• Absorb water, anchor the plant, and store sugars.
• Taproot systems have a single, large central root that goes deep into the ground.
• Fibrous root systems consist of many thin roots that spread out near the soil surface.

Plant Tissues

• Tissues are groups of cells performing specialized functions.
• Xylem transports water and minerals upward from the roots.
• Phloem transports sugars and nutrients from leaves or storage tissues to other parts of the plant.

Meristems

• Meristems are unspecialized tissues that divide, producing new cells for growth and specialization.
• Apical meristems, located at root tips and shoot buds, enable plants to lengthen vertically (primary growth).

Vascular Plants (Tracheophytes)

• Terrestrial plants capable of storing water in cells.
• Transport water and nutrients over long distances via stems, roots, and leaves.

Non-Vascular Plants (Bryophytes)

• Live in damp environments.
• Lack vascular bundles for water transport.
• Lack true stems, roots, or leaves.

Transportation

• Plants lose water vapor through stomata, tiny openings.
• Guard cells regulate stomata openings to control air and water passage.
• The waxy cuticle reduces water loss through transpiration.

Plant Evolution

• Modern land plants evolved from green algae (charophytes).
• Early plants lacked vascular tissue and depended on water.
• Mosses (bryophytes) were the first land plants, lacking vascular tissue and reproducing via spores in moist environments.
• Ferns (pteridophytes) were the first vascular plants, reproducing via spores in moist environments.

Gymnosperms and Angiosperms

• Both produce seeds, with gymnosperms bearing naked seeds inside cones and angiosperms enclosing seeds inside fruits.
• Utilize wind pollination; angiosperms also use insects and animals for pollination.

Alternation of Generations

• Plants alternate between a haploid gametophyte (n) stage, producing gametes through mitosis, and a diploid sporophyte (2n) stage, producing sporangia through meiosis.

Plant Adaptations: Pollen Grains

• Allow plants to reproduce without water, carried by wind or animals.
• Pollen contains sperm-producing cells, transferred through pollination.

Flower Structure

• Flowers have male, female, and non-reproductive parts for plant reproduction.
• Carpel (Pistil): Female reproductive structure with stigma (pollen landing surface), style (tube to ovary), and ovary (containing ovules).
• Anther: Male part of the stamen that produces and releases pollen containing sperm cells.
• Sepals: Non-reproductive, green leaf-like structures that protect the flower bud.
• Ovary: Enlarged base of the carpel containing ovules that develop into seeds, and becomes the fruit for protection and seed dispersal.

Photosynthesis

• Occurs in the chloroplasts.
• Light reactions generate ATP and NADPH using sunlight.
• Calvin cycle (dark reactions) uses ATP and NADPH to convert CO2 into glucose.
• 6CO2 + 6H2O + light energy → C6H12O6 + 6O2
• Performed by autotrophs (plants and algae), converting sunlight into glucose and producing oxygen.

Cellular Respiration

• Happens in the mitochondria.
• C6H12O6 + 6O2 → 6CO2 + 6H2O + ATP
• Both autotrophs and heterotrophs use it to break down glucose and release energy as ATP.

Interconnection of Photosynthesis and Cellular Respiration

• Oxygen from photosynthesis is used in cellular respiration, and carbon dioxide from cellular respiration is used in photosynthesis.
• Cellular respiration breaks down glucose to release energy.
• Photosynthesis creates glucose and oxygen.
• Requires oxygen and not carbon dioxide.

Photosynthesis Pathways

• C3: cool, moist environments.
• C4: hot, sunny environments.
• C5: dry environments.

Light Absorption

• Red and blue light are most effective for photosynthesis.
• Chlorophyll absorbs specific wavelengths of light.
• Carotenoids (orange) and xanthophylls (yellow) help absorb light.

Chromatography

• Used to separate pigments.
• Carotene is the most soluble pigment and moves farthest on the paper.
• RF value = pigment distance / solvent distance, indicating how far a pigment traveled relative to the solvent.