Plant section exam

Plant Section Exam #3 Study Guide

Introduction to Plant Systems

  1. How do land plants adapt to terrestrial life?
       - Dry Out: Plants develop a waxy cuticle and stomata to prevent water loss.
       - Moving Water:
         - Bryophytes are limited in size because they lack vasculature.
         - Tracheophytes evolved specialized vascular tissues to transport water and nutrients over long distances.
         - Xylem: Conducts water.
         - Phloem: Transports sugars and dissolved nutrients.
       - UV Radiation:
         - To deal with mutations caused by UV radiation, plants shifted to a dominant diploid generation, allowing deleterious recessive mutations to be masked.

  2. Describe and label the generalized haplodiplontic lifecycle
       - Germination and Mitotic Cell Division:
         - Spores (n) undergo meiosis from the 2n spore mother cell in sporangia.
         - Gametophyte:
           - Multicellular haploid (n) stage.
           - Spores divide by mitosis to produce this generation, which produces gametes (sperm and eggs) via mitosis.
           - Fertilization: Gametes fuse to form a diploid zygote (2n), which is the first cell of the next sporophyte generation.
       - Sporophyte (2n):
         - Diploid stage.
         - Diploid sporocytes undergo meiosis to produce four haploid spores.
         - The diploid sporophyte embryo has two copies of each gene.

  3. What is a bryophyte?
       - Closest living descendants of the first land plants, known as non-tracheophytes because they lack tracheids (water-conducting cells).
       - Includes: liverworts, mosses, and hornworts.

  4. What are the major characteristics of bryophytes?
       - Dominant Gametophyte: Small visible generation specialized for photosynthesis.
       - Size Limitation: Limited in size due to the lack of vascular system.
       - Dependent Sporophyte: Small sporophyte grows from the surface of the gametophyte, relying on it for nutrition while specializing in spore dispersal.
       - Symbiotic Help: Mycorrhizal associations (symbiosis with fungi) are important for enhancing water intake.

  5. What is a tracheophyte?
       - Vascular plants classified into three clades:
         1. Lycophytes: Club mosses.
         2. Pterophytes: Ferns, whisk ferns, and horsetails.
         3. Seed Plants:
       - The gametophyte is reduced in size due to the evolution of sporophytes in tracheophytes.

  6. What are the major characteristics of tracheophytes?
       - Dominant Sporophyte: The diploid sporophyte is the dominant generation.
       - Vascular Tissues: Possess xylem and phloem for internal transport.
       - Complex Structure: The sporophyte features well-differentiated roots, stems, and leaves.
       - Reduced Gametophyte: Over evolutionary time, the gametophyte has been significantly reduced in size relative to the sporophyte.

  7. Significance of Xylem and Phloem
       - Xylem: Conducts water and dissolved minerals upward from the roots.
       - Phloem: Transports sugars and dissolved nutrients or hormones throughout the plant.
       - The presence of these tissues allows tracheophytes to attain greater height.

  8. What are the land plant innovations that separate bryophytes and tracheophytes? What is the primary function for each?
       - Innovation: Vascular Tissues.
       - Stems, Roots, Leaves:
         - Function: Distributes water (xylem) and nutrients (phloem), enabling larger growth.
       - Dominant Sporophyte:
         - Function: Provides structural support, nutrient absorption, and maximizes surface area for photosynthesis.
       - Protection against UV-induced mutations: Allows for greater structural complexity.

Plant Form

  1. What are the three basic plant tissue types, and what are their general functions?
       - Ground Tissue: Functions in storage, photosynthesis, and secretion.
       - Dermal Tissue: Outer protective cover of the plant.
       - Vascular Tissue: Conducts fluid and dissolved substances throughout the plant.

  2. What is a meristem?
       - A clump of cells with dense cytoplasm and large nuclei that act similarly to animal stem cells.
         - When a meristematic cell divides, it produces one cell that differentiates and another that remains meristematic.
       - Apical vs. Lateral Meristems:
         - Apical Meristems: Located in the tips of stems and roots, responsible for the length of the plant body and give rise to primary tissues.
         - Lateral Meristems: Found in plants exhibiting secondary growth, producing an increase in diameter of the shoot and root.

  3. What are the three primary meristems?
       - Derived from apical meristems:
         1. Protoderm: Gives rise to the epidermis.
         2. Procambium: Gives rise to primary vascular tissue.
         3. Ground Meristem: Gives rise to ground tissue.

  4. What are the secondary meristems called?
       - Cork Cambium: Produces secondary vascular tissues.
       - Vascular Cambium: Produces secondary vascular tissues.

  5. What are Parenchyma, Collenchyma, and Sclerenchyma?
       - Cell types that make up ground tissues:
         - Parenchyma: Most common, functions in storage, photosynthesis, and secretion. Most have only primary cell walls and are less specialized than other plant cells.
         - Collenchyma: Provides flexible support and protection for plant organs. Lacks secondary cell walls.
         - Sclerenchyma Cells: Provides rigid support and protection with tough thick walls.
           - Two general types:
             1. Fibers: Long slender cells usually grouped in strands.
             2. Sclereids: Variable shape, often branched, found singly or in groups.

  6. What are the basic characteristics of dermal tissue?
       - Forms the epidermis, one cell layer thick, covered by a waxy cutin layer to prevent water loss.
       - Contains special cells:
         - Guard Cells: Flank stomata for gas exchange.
         - Trichomes: Hairline outgrowths that reduce evaporation and deter herbivores.
         - Root Hairs: Increase surface area for absorption.

  7. What are the basic characteristics of vascular tissues?
       - Consists of two main types of conducting tissues:
         1. Xylem: Conducts water and dissolved minerals throughout the plant.
            - Includes vessels (dead, hollow tubes) and tracheids (dead tapering overlapping cells).
         2. Phloem: Conducts food and transports hormones and amino acids for plant growth.
            - Sieve cells/Sieve-tube members associated with companion cells.

  8. What are the functions of the root cap?
       - Columella Cells: Inner root cap cells.
       - Outer and Lateral Cells: Primarily function in protecting delicate tissues behind it as growth extends the root through abrasive soil particles.
       - Perception of Gravity: Helps the plant understand its orientation relative to gravity.

  9. Modified Roots:
       - Taproot System: A single large root with many small branch roots.
       - Fibrous Root System: Many small roots of similar diameter.

Photosynthesis

  1. What is a photon?
       - A particle of light or light as an electromagnetic wave, forming a continuous spectrum of radiation known as the electromagnetic spectrum.

  2. What are the pigments used in green plants? How do they support photosynthesis?
       - Chlorophylls (a and b): Reflect green light while primarily absorbing blue and red light.
       - Carotenoids: Orange accessory pigments.
       - Pigments support photosynthesis by light absorption.
       - Energy Transfer: Carotenoids absorb light and transfer that energy to chlorophyll.
       - Carotenoids also act as antioxidants, preventing light from causing oxidative damage to chlorophyll molecules.
       - Without them, photosynthesis cannot occur effectively in the presence of oxygen.

  3. What happens in the chloroplasts during photosynthesis?
       - Light-Driven Reactions:
         - Occur in thylakoid membranes.
         - Starting products: Light and water (H₂O).
         - Ending products: Oxygen (O₂), ATP, NADPH.
       - Carbon Reactions:
         - Occur in the stroma.
         - Starting products: Carbon dioxide (CO₂), ATP, NADPH.
         - Ending products: Carbohydrates ((CH₂O)n, such as sugars).
         - Returns ADP + P and NADP+ to the light reactions.

  4. What are the two components of the photosystem?
       - Antenna Complex:
         - Hundreds of accessory pigment molecules.
         - Gathers photons and keeps the captured light energy to the reaction center.
       - Reaction Center:
         - Contains one or more chlorophyll a molecules.
         - Passes excited electrons out of the photosystem.

  5. What are the reactants and products of Photosystem II (PSII)?
       - Photosystem II:
         - Reaction center is P680.
         - Uses light energy to oxidize water (the reactant), producing oxygen (O₂) and energized electrons.
       - Photosystem I (PSI):
         - Reaction center is P700.
         - Receives electrons from the transport chain and uses light energy to produce NADPH (product).

  6. What are the reactants and products of the Calvin cycle? What is the function of rubisco?
       - Reactants: Carbon dioxide (CO₂), ATP, NADPH.
       - Products: Glyceraldehyde 3-phosphate (G3P), a three-carbon sugar used to make glucose, sucrose, and starch.
       - Returns ADP and NADP+ to light reactions.
       - Rubisco: The enzyme responsible for the key step of attaching CO₂ to a 5-Carbon sugar (RuBP) to begin the carbon fixation phase.
         1. Carbonylation: Normal conditions with adding CO₂ to RuBP.
         2. Photorespiration: Hot conditions with adding O₂ to RuBP.

  7. How does ATP synthesis occur?
       1. Accumulation of protons (H+).
       2. Creation of Gradient.
       3. Activation of ATP Synthase.
       4. Mechanical energy is used to produce ATP.

Transport in Plants

  1. What travels in xylem? In what direction is flow in these cells?
       - Xylem: Transport water and dissolved minerals upward from roots to leaves/stems.
       - Flow is unidirectional and in one direction (up).

  2. What travels in phloem? In what direction is the flow in these cells?
       - Phloem: Transport organic nutrients (sucrose produced via photosynthesis and amino acids).
       - Flow is bidirectional, transporting nutrients both up and down, contrary to the unidirectional flow of xylem.
       - Phloem Transport: Sucrose, amino acids, and hormones throughout plants via translocation from source (leaves) to sink (roots).

  3. What is transpiration & how does it play a role in transport in plants?
       - Transpiration: Evaporation of water from leaves.
       - Water evaporates from the leaves out of the stomata, which must be open to let CO₂ needed for photosynthesis.

  4. What is translocation and its role in transport in plants?
       - Translocation: Movement of sugars made through photosynthesis in the leaves.
       - Role: Provides building blocks for actively growing regions of the plant.

  5. What is an aquaporin?
       - Water-selective pores in the plasma membrane that increase the rate of osmosis via water diffusion, without changing the direction of water flow.

  6. What does it mean when a plant cell becomes turgid, and what role does this process serve?
       - Turgid State: Happens when a plant cell expands due to water intake.
       - Role: When a cell is placed in a hypotonic solution (higher solute concentration), water moves into the cell by osmosis, causing it to become turgid.

  7. What is water potential?
       - Water potential measures the potential energy of water per unit volume and moves from higher to lower potential.

  8. What are the three transport routes that exist between cells?
       1. Apoplast Route: Movement through the cell wall and the space between cells, avoiding membrane transport.
       2. Symplast Route: Movement through the cytoplasm continuum where cells are connected by plasmodesmata.
       3. Transmembrane Route: Movement across the membranes of cells and vacuoles, with the greatest control over materials passing through.

  9. What drives ion uptake in plants? Why is this necessary?
       - Ion Uptake: Driven by active transport using proton pumps, which move ions against a concentration gradient (from low to high), requiring ATP.
       - Passive Transport: Movement of substances across a cell membrane (from high to low concentration) and does not require ATP.
       - Necessary because the concentration of mineral ions in soil water is lower than that inside the plant, requiring energy to move them against their concentration gradient into the plant.

  10. What is the pressure-Flow hypothesis?
       - The most widely accepted model describing the movement of carbohydrates in phloem.
       - Dissolved carbohydrates move from sources to sinks.
       - Active transport loads sucrose into sieve tubes at the source and water follows by osmosis, increasing turgor pressure, which drives fluid throughout the plant to the sink.

Transport of Water and Sugar

  • CO₂ and light enter through stomata.

  • Water and minerals enter through roots.

  • Photosynthesis Produces Carbohydrates:
       - Carbohydrates travel in the phloem.
       - Water travels up xylem.
       - Water exits through stomata as vapor during transpiration.

Plant Nutrition

  1. What is topsoil?
       - The uppermost layer of soil where roots are found.
       - A mixture of mineral particles of varying sizes, living organisms, and humus.
       - Characterized by relative amounts of sand, silt, and clay, which determines the degree of water and nutrient binding to soil particles.

  2. What happens when topsoil is lost? What are some methods to prevent topsoil loss?
       - Loss of topsoil adversely affects the soil's water-holding capacity and nutrient content.
       - Methods to Prevent Topsoil Loss:
          - Intercropping: Mixing crops in a field.
          - Conservation Tillage.
          - No-Till: Leaving crop stubble in the field.

  3. What is a macronutrient? Micronutrient?
       - Macronutrient: Used in relatively large amounts for energy and development.
       - Micronutrient: Used in minute amounts, primarily for trace enzyme function and metabolism.

  4. What is hydroponics?
       - A soil-free cultivation method that grows plants in a nutrient-rich water solution, allowing for faster growth and higher yields.

  5. What are the three special nutritional strategies we discussed in class?
       - Plants need ammonia (NH₃) or nitrate (NO₃) to build amino acids, often supported by nitrogen-fixing bacteria.
       - Mycorrhizae are found in 90% of vascular plants, forming symbiotic relationships that enhance nutrient uptake.

  6. Why is more plant photosynthesis not necessarily a good thing?
       - Excessive photosynthesis can harm ecosystems and lower the quality of food production.

  7. What is phytoremediation? What are the three main types?
       - Phytoremediation: The use of plants to concentrate or breakdown pollutants.
         - Types:
           1. Phytodegradation: Contaminant is taken up from soil and broken down.
           2. Phytovolatilization: Contaminant is taken up from soil and released through stomata.
           3. Phytoaccumulation: Contaminant is taken up from soil and concentrated in shoots, which are later harvested.