Chapter 13 Plants: Uses, Form, and Function - Vocabulary Flashcards

13.1 Plants as Valuable Bioresources

• Plants make possible almost every daily activity by providing food, clothing, shelter, medicine, and oxygen. They support life on Earth through photosynthesis and cellulose, and underpin many ecosystem services.

• Biosphere dependence on plants

  • Ecosystem services provided by plants include food and habitat for other organisms, oxygen production via photosynthesis, fiber for clothing and structures, reduced soil erosion, and fuel sources.

  • Two key ecosystem services: photosynthesis and cellulose (the latter is a major plant carbohydrate). Photosynthesis: 6CO2+6H2O+light→C6H12O6+6O2

• Photosynthesis as a life-sustaining process

  • Plants, some bacteria, and some protists perform photosynthesis.

  • Plants convert solar energy into chemical energy, producing glucose (energy source) and oxygen.

  • Plants are producers and form the base of many food chains.

  • Plants emit oxygen: most of the atmosphere’s oxygen comes from photosynthesis; estimate: about $50\%$ of atmospheric O₂ is produced by plants.

• The many uses of cellulose

  • cellulose is a large carbohydrate and the main component of plant cell walls.

  • Human uses include textiles (cotton), paper and cardboard (wood pulp).

  • Energy release when burning plant materials arises from chemical energy stored in cellulose.

• Food and agricultural context

  • Agriculture: farming/forestry practices that produce food and goods.

  • Global crop usage: only a small fraction of edible plant species are used commercially (roughly $150/50{,}000\approx 3\times 10^{-3}$ or about 0.3%).

  • The average human diet relies on about $20$ major crop plants; wheat, rice, and corn account for about $60\%$ of plant-based calories.

  • Other important crops include sugar cane, potatoes, sugar beets, soybeans, and barley.

• Canada and plants

  • Canada’s agricultural sector provides food and jobs; about $1/7$ of Canadian jobs are agricultural-related.

  • Agriculture and food sectors contribute roughly $10\%$ of Canada’s GDP.

  • Canada exports agricultural products globally; notable example: maple sugar and maple syrup exports exceed $200\,\text{million dollars}$ annually.

• Aboriginal agriculture: the Three Sisters

  • Corn, climbing beans, and squash planted together form a symbiotic system.

  • Corn provides vertical structure for beans to climb; beans fix atmospheric nitrogen, enriching the soil for corn and squash.

  • Squash provides ground cover, protecting against dehydration, weeds, and pests.

• Important Canadian crops and products (Table 13.1 highlights)

  • Wheat: production around $28{,}611\text{ thousand tonnes}$; flour used for pasta, bread, cereal, cakes, cookies.

  • Canola: around $12{,}642\text{ thousand tonnes}$; primary product canola oil.

  • Barley: $11{,}781\text{ thousand tonnes}$; used in soups, salads, stews; flour for baked goods.

  • Grain corn: $10{,}592\text{ thousand tonnes}$; cornmeal, cereal, tortillas chips.

  • Oats: $4{,}272\text{ thousand tonnes}$; oatmeal, oat bran; flour for cereal, muffins, cookies.

  • Peas: $3{,}571\text{ thousand tonnes}$; eaten alone or in dishes.

  • Soybeans: $3{,}335\text{ thousand tonnes}$; soy products and flour for baked goods.

  • Lentils: $1{,}043\text{ thousand tonnes}$; eaten alone or in soups.

  • Flaxseed: $861\text{ thousand tonnes}$; flaxseeds and flaxseed oil.

  • Rye: $316\text{ thousand tonnes}$; flour for cereal and baked goods.

• Food security and monoculture vs. sustainable agriculture

  • By 2030–2050, global population projections reach $8-9\times 10^{9}$; food security becomes critical.

  • Monoculture advantages: simplifies management, potential for higher yields; major drawbacks: soil nutrient depletion, greater reliance on synthetic fertilizers and pesticides, water quality concerns due to runoff, and vulnerability to pests.

  • Sustainable agriculture aims to balance high yields with ecological, economic, and social considerations.

  • Practices include crop rotation, use of natural predators for pest control, reduced machinery use (e.g., weed hand-pulling), and supporting local communities.

• Plants as a source of fibres and building materials (Table 13.2 and related ideas)

  • Plant fibres used to produce paper, cardboard, rope, fabrics/textiles, and timber products.

  • Key materials from plant fibres include: paper (wood chips, fibrous crops; pulp-based), cardboard (high-quality paper with lignin left in), rope (textiles and cord; high-quality rope historically from Indian hemp), fabrics/textiles (cotton, flax linen), and timber (lumber, plywood, particleboard, fiberboard).

  • Straw from straw-bale construction serves as walls and insulation; straw is renewable on a short timescale, inexpensive, readily available, and a good insulator.

  • Wood remains the most common building material globally; other plant-based building materials include straw bales.

• Plant-based fuels and erosion control; ecotourism

  • Biofuels: Canada is exploring biofuels produced from renewable biological sources (e.g., crops and crop residues).

  • Ethanol and biodiesel as examples of biomass-derived fuels; pros and cons discussed in various forums (e.g., Quirks & Quarks feature).

  • Plants contribute to erosion control by stabilizing soil with roots and canopy cover, reducing soil loss and surface runoff; vegetation slows water movement and promotes infiltration.

  • Plants, recreation, and ecotourism: Canada’s landscapes and plant diversity support hiking, camping, parks, and ecotourism(
    including boreal forests, temperate rainforests, and prairies).

• Medicinal plants and biochemicals (highlights from Section on Plant Biochemicals)

  • Traditional and Aboriginal uses of plant extracts for medicines, perfumes, and dyes.

  • Modern industry: ~25% of prescription medicines contain plant extracts or are derived from plant compounds; ongoing discovery and synthesis of plant-based medicines.

  • Rosy periwinkle (Catharanthus roseus) source of vincristine and vinblastine; significant cancer treatment impact but species at risk due to habitat loss from deforestation (Madagascar).

  • Examples of other medicinal plants include ginseng (immune system) and goldenseal (cold/ throat therapies).

  • Deforestation and biodiversity loss threaten undiscovered plant-derived medicines; need for sustainable harvesting and biodiversity conservation.

• Biofuels and industry notes (Quirks & Quarks summary)

  • Biomass resources (e.g., agricultural residues, wood waste) have potential as energy sources but challenges include energy density, logistics, and competing land use.

  • Some projects show promising ethanol yields from straw and switchgrass, but scale requires large investments and careful resource planning.

• Ethical, philosophical, and practical implications

  • Balancing human energy needs with biodiversity conservation and environmental sustainability.

  • Indigenous and local communities’ rights and knowledge in plant use and land management.

  • The need for sustainable harvesting and fair access to plant-based resources, particularly for medicines and traditional uses.

  • Economic considerations: monocultures versus diversified farming, local employment, and community resilience.

13.2 The Vascular Plant Body

• Plants are composed of specialized cells organized into tissues, which form organs and systems.

• Plant organization overview

  • Two major plant groups: vascular (vascular tissues present) and non-vascular (no true vascular tissue).

  • Vascular plants have two organ systems: shoot system (stems and leaves) and root system (roots).

  • The shoot system supports photosynthesis and reproduction; the root system anchors the plant and absorbs water and minerals.

• Plant cell basics

  • Plant cells have a cell wall, a large central vacuole, and chloroplasts (sites of photosynthesis).

  • Major tissue types include meristematic tissue, dermal tissue (epidermis and periderm), ground tissue, and vascular tissue (xylem and phloem).

• Meristematic tissue

  • Regions of rapid cell division; provide undifferentiated cells that can develop into other tissues.

  • Apical meristems drive primary growth (lengthening of stems and roots).

  • Intercalary meristems (in some plants like grasses) allow continued growth after mowing.

  • Lateral meristems (vascular cambium and cork cambium) enable secondary growth (girth increase) and production of wood/bark.

• Dermal tissue

  • Outer protective covering; includes epidermis and periderm (cork) in older, woody plants.

  • Guard cells regulate stomatal openings (stoma) for gas exchange; stomata control CO2 uptake, O2 release, and water vapor loss.

  • Trichomes (epidermal hairs) reduce evaporation and may secrete deterrents/toxins.

  • Root hairs increase surface area for water and nutrient uptake.

• Ground tissue

  • Broadly functional; includes parenchyma (storage, photosynthesis in leaves, soft tissues), collenchyma (flexible support), sclerenchyma (thick-walled, lignified for support; includes fibers and sclereids).

• Vascular tissue

  • Internal transport system consisting of xylem and phloem.

  • Xylem transports water and minerals from roots to tops; composed of tracheids and vessel elements (dead at maturity in angiosperms; vessel elements form continuous tubes; pits allow movement between cells).

  • Phloem transports sugars (organic molecules) from leaves to other parts of the plant (sources to sinks); composed of sieve tube elements (living but with no nuclei) and companion cells that support living function.

• Plant cell types (Table 13.3 overview)

  • Parenchyma: storage, photosynthesis, gas exchange, protection; often alive at maturity; chloroplast-rich in leaves.

  • Collenchyma: flexible support; unevenly thickened walls; allows bending without breaking.

  • Sclerenchyma: thick, lignified secondary walls; often dead at maturity; provides mature support; two forms: sclereids (gritty pears, seed coats) and fibers (rope textiles).

• Visualize plant tissues (Fig. 13.8, Fig. 13.12, Fig. 13.13, etc.)

• Key terms

  • meristematic tissue, dermal tissue, epidermis, guard cell, stoma, root hairs, ground tissue, xylem, phloem, parenchyma, collenchyma, sclerenchyma, vascular tissue, sieve tube element, companion cell.

13.3 Plant Organs and Their Functions

• Three basic plant organs and their roles

  • Roots: absorb water and minerals, anchor the plant, store carbohydrates; can comprise more than half of a plant's mass in some species.

  • Stems: provide structural support for leaves and reproductive parts; transport vessels between roots and leaves; enable growth in length and girth.

  • Leaves: main site of photosynthesis; large surface area; specialized internal structure to maximize light capture and chemical energy production.

• Root structure and function

  • Root tip is covered by the root cap (protects growing tissues and secretes slime to ease movement).

  • Apical meristem drives elongation; primary growth.

  • Cortex, endodermis, and Casparian strip regulate water and mineral entry into the vascular system.

  • Inner vascular tissue (xylem and phloem) arrangement differs between monocots and dicots:

  • Monocots: xylem forms a ring around a pith; phloem surrounds the ring.

  • Dicots: xylem forms a central star or X; phloem fills spaces between arms.

• Root systems

  • Two major root system types: taproot (a thick primary root with lateral branches) and fibrous (many small roots from a common point).

  • Taproots are associated with food storage (e.g., carrots); deep-water access in dry environments.

  • Fibrous roots commonly found in grasses; shallow but widespread.

  • Modifications for storage or adaptation: water storage roots; aerenchyma in aquatic plants for gas exchange.

• Stems

  • Types of stems include herbaceous (soft) and woody (rigid, with secondary growth).

  • Stem adaptations: tubers (potatoes) store nutrients; bulbs (onions) store nutrients and have enlarged bases; corms; stolons (runners like strawberries); rhizomes (underground stems).

  • Woody stems show annual growth rings (from xylem) reflecting yearly environmental conditions.

• Leaves

  • Structure: blade with petiole; cuticle reduces water loss; leaf venation patterns (parallel in monocots; palmate/pinnate in dicots).

  • Internal structure: mesophyll includes palisade (dense chloroplasts; main photosynthesis) and spongy (air spaces for gas exchange); guard cells regulate stomata.

  • Leaf adaptations include trichomes for cooling and deterring herbivores; variations in leaf shape and venation reflect species adaptations.

• Monocots vs. Dicots (Section 13.3 comparison)

  • Monocots: one cotyledon; vascular tissue arranged in scattered bundles; parallel venation; floral parts in multiples of three; fibrous roots; examples include grasses and lilies.

  • Dicots: two cotyledons; vascular tissue arranged in rings (stem) and star-shaped in roots; palmate or pinnate venation; floral parts in multiples of four or five; usually taproot; examples include beans, oaks, roses.

• Visualization and activities

  • Activity 13-B: Compare and contrast monocot and dicot stems through prepared slides and growth rings in woody vs. herbaceous dicot stems.

  • Investigation: Observe monocot and dicot stem tissues; analyze vascular bundle arrangements; infer growth patterns and age.

• Section Summary (13.3)

  • Root system anchors and absorbs; shoot system (stems/leaves) provides support and transport; stems can be modified to store food or water; leaves perform photosynthesis with specialized internal structures.

13.4 Transport in Plants

• Core idea

  • Vascular plants contain a conducting system to transport fluids and nutrients across the plant via two tissues: xylem (water/minerals) and phloem (organic nutrients, primarily sugars).

• Transport mechanisms (short-distance vs. long-distance)

  • Short-distance: active transport, diffusion, and osmosis move water and solutes across cells.

  • Long-distance: two models explain movement through vascular tissue:

  • Cohesion-tension model (xylem): transpiration in leaves creates negative pressure pulling water upward; relies on cohesion of water molecules and adhesion to xylem walls.

  • Pressure-flow model (phloem): translocation moves sugars from source to sink via positive pressure generated by osmosis at the source.

• Xylem transport (upward movement of water and minerals)

  • Root uptake creates higher solute concentration inside roots; water moves by osmosis into root cells; water and minerals move through intercellular spaces into the xylem.

  • Water moves upward through the xylem; entry into leaves occurs via diffusion into leaf tissues.

  • In leaves, most water is lost to the atmosphere via transpiration through stomata (often > $90\%$ of water reaching leaves is lost as water vapor).

  • Mechanisms enabling long-distance transport include:

  • Root pressure: positive pressure generated by water and solute accumulation in xylem; can cause guttation in small plants when humidity is high.

  • Transpiration: evaporation from leaf surfaces creates a negative pressure that pulls water up the plant.

  • Cohesion: water molecules in xylem form cohesive columns that resist breaking under tension.

  • Adhesion: water molecules adhere to xylem walls, aiding column stability.

• Phloem transport (movement of sugars and other organic molecules)

  • Translocation moves sugars from sources (e.g., mesophyll cells in leaves) to sinks (growth regions, storage tissues, roots).

  • Phloem anatomy: sieve tube elements (alive at maturity but lacking nuclei) and companion cells that support sieve tube elements.

  • Pressure-flow model details: loading sucrose into sieve tubes at the source draws water into the tube by osmosis, increasing pressure and pushing the sap toward a sink; at the sink, sucrose is unloaded and water exits, reducing pressure; flow can be bidirectional if needed by different sources/sinks.

  • A classic model setup (two connected bulbs) demonstrates pressure differences driving flow through a porous membrane.

• Practical investigations and models

  • Activity 13.3: Modelling transpiration with dyed water in cut stems, using a fan to simulate air movement and observe color movement in plant tissue.

  • Investigation prompts to draw and label the cohesion-tension and pressure-flow mechanisms and to explain observed results.

• Section Summary (13.4)

  • Water and minerals move through xylem; sugars (organic nutrients) move through phloem.

  • Active transport, osmosis, and diffusion underpin short-distance transport; cohesion-tension explains long-distance water movement; pressure-flow explains translocation of organic molecules.

Connections and broader implications

• Linking sections

  • Photosynthesis (13.1) provides the glucose that travels through phloem (13.4) to supply growth and storage tissues.

  • Cellulose (13.1) underpins plant structure and is a primary plant fiber source in 13.2 and 13.3 contexts.

  • Plant tissues (13.2) enable the specialized organs (13.3) to perform functions required for transport (13.4).

• Real-world relevance

  • Agriculture: monoculture vs sustainable practices (13.1) influences food security, soil health, and environmental impact.

  • Forestry and building materials: plant fibers and straw-bale construction illustrate sustainable choices in housing and industry (13.1).

  • Pharmacology and biodiversity: medicinal plants and biochemicals emphasize the importance of conserving plant diversity for health and future drug discovery (13.1).

  • Ecology and tourism: ecotourism and ecosystem services highlight the value of plant diversity in Canadian landscapes (13.1).

Quick reference formulas and key numbers (LaTeX)

• Photosynthesis (summary):6CO2+6H2O+light→C6H12O6+6O2

• Global oxygen contribution from plants: $ext{O}_{2} \text{ production by plants} \approx 50\%$ of atmospheric O₂.

• Edible plant species usage: $150/50{,}000 \approx 3\times 10^{-3}$ (about 0.3%).

• Diet diversity: about $20$ staple crops.

• Major global crop share: $60\%$ of plant-based calories come from wheat, rice, and corn.

• Population and food security (projected): $8\times 10^{9} \leq \text{population} \leq 9\times 10^{9}$ by 2030–2050.

• Monoculture concerns: no single formula, but conceptually: increased yield with higher input costs and environmental risks; expressed as qualitative trade-offs rather than a single equation.

• Wood use in straw-bale vs. stick-frame (example from Launch Activity):

  • Increase in wood use when using stick-frame vs straw-bale: \Delta = T{stick} - T{straw} = 16.17 - 10.96 = 5.21\ \text{m}^3\

  • Overall percentage increase: \% ext{Increase} = \frac{\Delta}{T_{straw}} \times 100\% = \frac{5.21}{10.96} \times 100\% \approx 47.5\%$$.

Suggested study prompts (from the transcript’s Review and Learning Checks)

• Distinguish root vs shoot system roles and identify their tissues.

• Describe how xylem and phloem differ in structure and function.

• Explain the cohesion-tension model and the role of transpiration.

• Compare monocots and dicots across embryonic leaves, venation, and root structure.

• Outline how leaves’ palisade and spongy mesophyll support photosynthesis and gas exchange.

• Discuss sustainable agriculture practices and give examples of their ecological and social benefits.

• Explain how plant fibers are used in building materials and textiles; give examples of specific fibers.

• Describe how medicinal plants are identified and conserved; discuss ethical considerations.

• Explain how to model phloem translocation using a pressure-flow concept.

• Compare the advantages and disadvantages of straw-bale construction versus wood-based construction.