Plant Bio Study Guide Questions

Can you describe 3 different ways that humans (and other animals) rely on plants for survival?

Food, medicine, and oxygen/habitat.

What does it mean for an organism to be described as an autotroph? Are all plants autotrophs?

Autotrophs make their own food via photosynthesis. Most plants are, but some are parasites (like ghost plants).

List the differences and similarities between prokaryotic cells and eukaryotic cells.

Similarities: Both have DNA and plasma membranes. Differences: Prokaryotes are small, lack a nucleus, and lack organelles. Eukaryotes are large, have a nucleus, and have organelles.

Which are the main attributes that can be ascribed to members of Kingdom Plantae?

Eukaryotic, multicellular, photosynthetic, cellulose cell walls, alternation of generations, store starch, and protected gametes.

Describe three key features of plant cells that differentiate them from animal cells.

Cell wall, plastids (like chloroplasts), and a large central vacuole.

What are plastids? Name 3 types of plastids and indicate what types of pigments they contain and briefly describe their function.

Specialized plant organelles. 1. Chloroplasts: green chlorophyll (photosynthesis). 2. Chromoplasts: colored pigments (attraction). 3. Amyloplasts: no pigment (store starch).

How are peroxisomes different from plastids?

Peroxisomes have a single membrane (for oxidative reactions like photorespiration). Plastids have a double membrane (for photosynthesis/storage).

What is a vacuole? Name 3 functions of the vacuole.

A fluid-filled sack with a single membrane. Functions: 1. Cell expansion (turgor pressure), 2. Store metabolites, 3. Site for metabolic reactions.

What are the main functions of plant cell walls? What are they made of? What are the differences between primary and secondary cell walls?

Function: Structure and protection. Made of: Cellulose. Primary wall: Flexible, formed first. Secondary wall: Rigid, formed later inside the primary wall, contains lignin.

How do plant cells divide? What is the role of the cell plate in plant cell division?

They divide from the inside out. The cell plate forms in the center to separate the two new daughter cells.

How do plants communicate through cell walls? What structures allow communication through plant cell walls?

Through plasmodesmata (cytoplasmic channels that cross cell walls).

Explain how polarity is established early in plant embryogenesis

The zygote divides asymmetrically into an apical and a basal cell, driven by auxin.

Explain what is apical-basal polarity and radial polarity of a plant embryo.

Apical-basal: Top-to-bottom axis (shoot-to-root). Radial: Inner-to-outer tissue layers.

What are the two stem cell populations that give rise to all postembryonic organs? For how long can these stem cells produce organs?

Shoot apical meristem (SAM) and root apical meristem (RAM). They can produce organs indefinitely.

What are the processes that occur at the end of embryogenesis? And why they are important?

Growth stops, food is stored, seed desiccates (dries out), and coat hardens. This triggers dormancy so the seed survives until favorable conditions.

What is seed germination? what environmental factors are especially important for breaking seed dormancy and allowed germination?

Germination is resuming metabolic activity to grow the radicle. Needs water, oxygen, and specific temperature/light.

What are the differences between primary and secondary growth?

Primary growth: Increases length (via apical meristems). Secondary growth: Increases thickness/girth (via lateral meristems).

Describe the three types of primary meristematic tissues that generate the three main types of plant tissues.

1. Protoderm -> Dermal tissue. 2. Procambium -> Vascular tissue. 3. Ground meristem -> Ground tissue.

What are the important features of meristems? How do they enable continuous and indeterminate plant growth?

They contain undifferentiated stem cells that continuously divide to supply new cells forever.

What are the three main types of tissue systems and what are their functions?

1. Dermal: Protection. 2. Vascular: Transports water/sugars. 3. Ground: Photosynthesis, storage, and support.

What are the main differences between xylem and phloem vascular tissues?

Xylem: Transports water (roots to shoots), dead at maturity. Phloem: Transports sugars (throughout plant), alive at maturity.

Describe the differences between the development of a xylem tracheary element and a phloem sieve tube element and its companion cell

Xylem: Dies, loses nucleus, forms rigid walls. Phloem: Stays alive, loses nucleus, but relies on a living companion cell for support.

What are the three types of cells in ground tissues and what is their function?

1. Parenchyma: Photosynthesis & storage. 2. Collenchyma: Flexible support. 3. Sclerenchyma: Rigid support.

Describe two types of specialized cell types in epidermal tissues and their function

1. Root hairs: Uptake water/nutrients. 2. Trichomes: Protect from insects, reflect light, hold humidity.

What are the main functions of root systems?

Anchorage, absorb water/minerals, and store food.

What are the differences between monocot and eudicot root systems?

Monocots have fibrous roots and no secondary growth. Eudicots have taproots and can have secondary growth.

List the three growth regions of the root, and describe the processes that are characteristic of each region.

1. Meristematic zone: Cell division. 2. Elongation zone: Cells lengthen. 3. Maturation zone: Cells specialize (root hairs form).

What is the root cap? And what is its function?

A layer of cells that protects the root apical meristem as it pushes through soil.

What is the role of border cells and columella cells?

Columella cells: Sense gravity. Border cells: Detach to protect the root and interact with soil.

Describe the movement of a solute from the surface to the center of a root, listing all tissues and potential pathways through which the solute may pass.

Tissues: Epidermis -> Cortex -> Endodermis -> Pericycle -> Xylem. Pathways: Apoplast (cell walls) or Symplast (cytoplasm/plasmodesmata).

Describe the composition, precise location, and role of the Casparian strip.

A waterproof band in the endodermis cell walls. It blocks the apoplast pathway, forcing water/solutes to cross a cell membrane.

What are the main features of the shoot apical meristem (SAM)?

Located at the shoot tip. Contains stem cells that produce primary tissues, leaves, and buds.

Consider the 3 main types of primary vasculature in the stem of most seed plants. What are the main differences between them?

Monocots: Scattered vascular bundles. Eudicots: Vascular bundles in a distinct ring (allows secondary growth).

Discuss how simple leaves are different from compound leaves.

Simple leaves have one undivided blade. Compound leaves have a blade divided into multiple leaflets.

What are the main differences in leaf venation in monocots versus dicots?

Monocots: Parallel veins. Dicots: Netted (branching) veins.

Describe the sequence of events that culminates in leaf abscission.

Cues trigger it -> nutrients move back to stem -> enzymes break down the separation layer -> a protective scar forms -> leaf falls off.

Describe three examples of leaf modifications and three examples of stem modifications.

Leaf: Spines (defense), tendrils (climbing), traps (carnivorous). Stem: Thorns (defense), tendrils (support), tubers/bulbs (storage).

What meristems are responsible for stem secondary growth and primary growth? And what is the role that each play in stem growth?

Primary growth (lengthening): Shoot apical meristem. Secondary growth (thickening): Vascular cambium and cork cambium.

What tissues are produced by the vascular cambium? And the cork cambium?

Vascular cambium: Secondary xylem (wood) and secondary phloem. Cork cambium: Cork and phelloderm (periderm).

How growth rings in wood are formed?

Seasonal variation in the vascular cambium: large cells in wet spring (early wood), small cells in dry summer (late wood).

What meristematic tissue generates the periderm? and what is the main function of the periderm?

Cork cambium generates it. Function: Acts as protective outer bark and uses lenticels for gas exchange.

Give an overview of the light reactions of photosynthesis. What are the main inputs and outputs of these reactions? Where do these reactions occur in the chloroplasts?

Location: Thylakoid membranes. Inputs: Light and H2O. Outputs: O2, ATP, and NADPH.

What are the photosynthetic pigments involved in photosynthesis? What type of light do they absorb? And how they transfer energy in the reaction centers?

Chlorophylls and carotenoids. Absorb: Blue and red light. Transfer: Pass solar energy to reaction centers to excite electrons.

What are the main protein complexes involved in the light reactions of photosynthesis? How do they work together to produce NADPH and ATP?

PSII, Cytochrome b6/f, PSI, and ATP synthase. Electrons flow through them to make NADPH, creating a proton gradient that drives ATP synthase to make ATP.

Give an overview of the carbon-fixation reactions of photosynthesis. What are the main inputs and outputs of these reactions? Where do these reactions occur in the chloroplasts?

Location: Stroma. Inputs: CO2, ATP, NADPH. Outputs: Carbohydrates (sugars).

Describe the three main stages of the Calvin-Benson Cycle. What enzyme is involved in the first stage and what is its main role?

1. Carboxylation (fixation), 2. Reduction, 3. Regeneration. Enzyme: Rubisco fixes CO2 onto RuBP.

How are the light and carbon-fixation reactions (Calvin-Benson cycle) linked to each other?

Light reactions make ATP and NADPH, which the carbon reactions use as energy to fix CO2 into sugars.

What is photorespiration? What is the main function of this process?

A wasteful process where Rubisco binds O2 instead of CO2. It limits photosynthetic efficiency in hot/dry conditions.

Compare and contrast C3, C4, and CAM photosynthesis. Why do we say that C4 plants separate carbon fixation and the Calvin-Beson cycle in space, and CAM plants separate them in time? What do C4 and CAM have in common, and how do they differ?

C3: Only Calvin cycle. C4: Separates fixation (mesophyll) and Calvin cycle (bundle-sheath) in SPACE. CAM: Separates fixation (night) and Calvin cycle (day) in TIME. Both C4/CAM minimize photorespiration.

What are the advantages and disadvantages of asexual versus sexual reproduction in plants?

Asexual: Fast and needs no mate, but lacks genetic variation. Sexual: Great genetic variation, but requires a mate and is energetically costly.

Describe the stages of a plant life cycle identifying which structures are haploid and diploid. What is the difference between a gametophyte and a sporophyte? In which one does meiosis occur? What are the products of meiosis? How are gametes formed?

Diploid Sporophyte -> Meiosis -> Haploid Spores -> Haploid Gametophyte -> Mitosis -> Haploid Gametes -> Fertilization -> Diploid Zygote.

Describe the steps in the formation of the male and female gametophytes from spores.

Spores undergo mitosis. Microspores become male gametophytes (pollen). Megaspores become female gametophytes (embryo sacs).

What are the organs that make up a flower? What are their functions?

1. Sepals: Protect bud. 2. Petals: Attract pollinators. 3. Stamens: Produce pollen (male). 4. Carpels: Contain ovary/eggs (female).

Describe the process of pollination in angiosperms. Why pollination does not always lead to fertilization?

Pollination is pollen transferring to the stigma. It doesn't guarantee fertilization because specific chemical signals are needed for the pollen tube to grow and reach the egg.

Describe the process of double fertilization in angiosperms. What are the products of this process and their functions?

Two sperm enter: 1 fertilizes the egg (forms diploid embryo), 1 fertilizes the central cell (forms triploid endosperm for seed nutrients).

Describe the ABC gene model that controls floral organ identity.

A = Sepals. A+B = Petals. B+C = Stamens. C = Carpels.

What is a fruit? What is their function? How are they formed?

A mature, ripened ovary formed after fertilization. Function: Protect seeds and aid in seed dispersal.

What are the similarities and differences of plant and animal hormones?

Similarity: Both are chemical signals that regulate growth in small amounts. Difference: Animal hormones come from specific glands, plant hormones can be made anywhere.

Name the 5 major types of plant hormones. Why are they considered growth regulators?

Auxin, Cytokinin, Gibberellin, Abscisic acid (ABA), Ethylene. They regulate growth by altering gene expression to control cell division and elongation.

Describe the 3 major steps of plant response to a stimulus. How do these steps occur at the whole plant level? And at the cellular level?

1. Reception (hormone binds receptor), 2. Transduction (signal amplified), 3. Induction (processes activated). Whole plant: One organ signals another. Cell: Receptor signals nucleus to change gene expression.

How does auxin regulate cell elongation in shoots and roots in response to tropisms?

Auxin accumulates on the shaded/lower side. In shoots: Promotes elongation (bends toward light). In roots: Inhibits elongation (bends downward).

Where is auxin synthesized? And how it imposes shoot apical dominance?

Synthesized in the shoot apical meristem. It travels down and suppresses lateral buds, keeping the plant growing upwards.

What are the main roles of cytokinins? Where are they synthesized?

Roles: Promote cell division, shoot formation, and delay aging. Synthesized in the roots.

How do auxin and cytokinins work together to promote plant growth in tissue culture? What is their role in cell elongation and division, and in root and shoot formation?

High Auxin = Root formation. High Cytokinin = Shoot formation. Together they regulate cell division and elongation.

What is the role of ethylene in fruit ripening? And why it is important for agriculture?

It is a gas that accelerates ripening. Important in agriculture to make fruits ripen simultaneously during transport.

Where is abscisic acid synthesized in plants? How it regulates the opening and closing of stomata?

Synthesized in response to stress. It makes K+ leave guard cells, so water leaves too, causing stomata to close.

Why are gibberellins important in seed germination? How do they play an opposite role than abscisic acid in this developmental process?

Gibberellins break dormancy and promote germination. ABA does the opposite (promotes dormancy and prevents germination).

What are the differences between primary and secondary metabolites? What is the importance of each?

Primary: Found in all cells, essential for basic life. Secondary: Found in specific cells, used for defense and chemical signaling.

What are the three main classes of plant secondary metabolites? What are some uses of each?

1. Terpenoids (essential oils, rubber). 2. Phenolics (lignin for strength, tannins). 3. Alkaloids (medicines like morphine, defense).

What are the criteria for determining an element is essential to plants?

Required to complete the life cycle, absence causes severe deficiency, and has an irreplaceable direct physiological role.

What is the difference between a macronutrient and a micronutrient? Describe one function of each plant macronutrient.

Macronutrients are needed in large amounts (e.g., Nitrogen for proteins/chlorophyll). Micronutrients are needed in trace amounts.

Explain why in some nutrient deficiencies, the older leaves display symptoms, whereas in other deficiencies, the younger leaves display symptoms.

Mobile nutrients (like Mg) move to young leaves, causing symptoms in OLD leaves. Immobile nutrients (like Iron) are stuck, causing symptoms in YOUNG leaves.

What are the main features of the A, B, and C horizons? Where are most roots found? And why?

A: Topsoil, rich in organics. B: Accumulates leached minerals. C: Weathering bedrock. Roots are mostly in Horizon A for water and nutrients.

What is nitrogen fixation? What are the main organisms responsible for this process? why is nitrogen fixation important for plant nutrition? In what biomolecules nitrogen is assimilated in plants?

Converting N2 gas into usable ammonium/nitrates via soil bacteria. Crucial because plants can't use N2 gas, but need nitrogen for amino acids and proteins.

Describe the sequence of events in which nitrogen-fixing root nodules are formed in plants.

Roots send chemical signals -> bacteria infect root hairs -> roots grow a nodule -> bacteria fix nitrogen inside.

Explain the mutualistic symbiosis between plants and mycorrhizae. How does it benefit the plant and the fungi?

Fungi get sugars from the plant. The plant gets massively increased surface area for absorbing water and nutrients (like phosphorus).

Compare short distance versus long distance transport of water and solutes in plants

Short-distance: Cell-to-cell (osmosis, apoplast, symplast). Long-distance: Bulk flow through vascular tissue (xylem/phloem).

What is water potential? What are the main factors determining water potential? How we can use water potential to determine the direction of water movement in plants?

It determines water flow. Water moves from high (less negative) to low (more negative) potential. Driven by solute concentration and physical pressure.

What is plant transpiration? And how do plants reduce transpiration?

Evaporation of water from leaves. Reduced by closing stomata, thick cuticles, or trichomes.

How do plants control stomatal opening and closing? What are the main environmental factors affecting this process? What is the role of water potential and K+ in stomatal opening and closing?

K+ enters guard cells -> water follows -> turgor increases -> stomata open. K+ exits -> water leaves -> stomata close. Affected by light, CO2, and water stress.

How does the cohesion-tension theory explain the transport of water from roots to leaves? What is the role of water potential? Where does the energy to drive this process comes from?

Evaporation creates negative tension that pulls a cohesive chain of water up the xylem. Energy comes purely from solar heat.

What are embolisms? How do they affect plant water transport in the xylem? What mechanisms plants use to prevent embolism spreading in the xylem?

Air bubbles that block water transport in the xylem. Plants trap them in single elements using bordered pits.

How does water enter the roots from soil? And what are the main pathways of water transport into the roots?

Water enters root hairs via osmosis. Pathways: Apoplast (walls), Symplast (cytoplasm), or Transmembrane.

Describe the long-distance transport of sugars in the phloem from source to sinks. How does the pressure flow hypothesis explain this process? What is phloem loading and unloading?

Sugars are loaded at sources -> water follows -> high pressure pushes sap to sinks -> sugars are unloaded.

What are the differences between “artificial” and “biological” classification systems? Give some examples of how plants are classified by each system.

Artificial: Based on human use/looks (e.g., "weeds"). Biological: Based on evolutionary ancestry (e.g., monophyletic clades).

How and why are phylogenetic analyses preferable to the way in which classifications were constructed previously? Explain the differences between the three types of phylogenetic classifications.

They show true evolutionary history. Monophyletic: Ancestor + ALL descendants. Paraphyletic: Ancestor + SOME descendants. Polyphyletic: No recent common ancestor.

Explain the difference between homologous and analogous characteristics. Why is it better to base an evolutionary classification system on homologous traits?

Homologous: Inherited from a common ancestor. Analogous: Evolved independently (convergent evolution). Homologous is better for mapping true genetic lineage.

What is the evidence for a common ancestor of land plants (Embryophytes) and green algae (charophyte, zygnematophyte, or coleochaete)?

Shared photosynthetic pigments, similar cellulose cell walls, and matching chloroplast DNA.

What are the main adaptations in the early history of plant evolution that contributed to the success of plants on land?

Protected embryos, waxy cuticle, stomata, lignin, and vascular tissue.

Explain three main features of non-vascular plants

No vascular tissue, no true roots/stems/leaves, and gametophyte-dominant life cycle.

How do mosses and liverworts differ from each other?

Mosses have leafy structures and stomata. Liverworts have flattened structures and no true stomata.

Describe the life cycle of a bryophyte (moss). Which structures are haploid or diploid? Which structures produce spores, male and female gametes? Why do mosses need water for reproduction?

Gametophyte (haploid) is dominant -> makes gametes. Sporophyte (diploid) grows on it -> makes spores. Need water for sperm to swim to the egg.

Explain the main features of seedless vascular plants

Sporophyte-dominant, have vascular tissue, no seeds, and need water for sperm.

Describe the evolution of microphylls and megaphylls. How do megaphylls differ from microphylls? What plant groups have megaphylls? What groups have microphylls?

Microphylls: Simple outgrowths with one vein (Lycophytes). Megaphylls: Fused branches with complex veins (Ferns, Gymnosperms, Angiosperms).

Describe the life cycle of a fern. Which structures are haploid or diploid? Which structures produce spores, male and female gametes? Why do ferns need water for reproduction?

Sporophyte (diploid) is dominant -> makes spores. Small independent Gametophyte (haploid) -> makes gametes. Needs water for sperm to swim.

How the alternation of generations in plants evolved from bryophytes, seedless vascular plants, to seed plants? Discuss with respect to both the sporophyte and the gametophyte.

Trend shifts from gametophyte-dominant (bryophytes) to sporophyte-dominant (seed plants), with the gametophyte shrinking until it's completely dependent on the sporophyte.

In what ways was the pollen such an important adaptation in the evolution of plants?

Protects sperm from drying out and allows wind/animal transport. Completely eliminates the need for water to reproduce!

What are the main functions of seeds? What are the main differences in the seeds of gymnosperms and angiosperms?

Function: Protect embryo, provide food, aid dispersal. Gymnosperms: Naked seeds on cones. Angiosperms: Seeds protected inside fruits.

What are the main characteristics of gymnosperms?

Vascular plants with "naked" seeds, no flowers/fruits, wind-pollinated, and sporophyte-dominant.

Describe the life cycle of a gymnosperm (conifer). Which structures are haploid or diploid? Which structures produce spores, male and female gametes? What adaptations allowed conifer reproduction without depending on water?

Tree (diploid) makes cones. Male cones make pollen (haploid). Female cones make ovules (haploid). Pollen tubes deliver sperm, eliminating the need for water.