Chapter 30: Plant Form and Physiology Flashcards
What are the three plant organs, and what are their primary functions?
Roots: Anchor plant, absorb water/nutrients, store food.
Stems: Support leaves/flowers, transport fluids (xylem/phloem).
Leaves: Photosynthesis, gas exchange (via stomata).
Describe the three tissue systems in plants.
Dermal: Outer protective layer (epidermis, cuticle).
Vascular: Transport tissues (xylem: water/minerals; phloem: sugars).
Ground: Storage, photosynthesis, support (parenchyma, collenchyma, sclerenchyma).
Compare primary vs. secondary growth.
Primary growth: Lengthening via apical meristems (roots/shoots).
Secondary growth: Thickening via lateral meristems (vascular cambium → wood; cork cambium → bark).
What are the key functions of stems?
Support leaves/flowers.
Transport water (xylem) and sugars (phloem).
Storage (e.g., tubers like potatoes).
Contrast monocot and eudicot stem anatomy.
Monocot: Vascular bundles scattered; no secondary growth.
Eudicot: Vascular bundles in a ring; secondary growth possible.
What is the role of the vascular cambium?
Produces secondary xylem (wood) and secondary phloem (inner bark) during secondary growth.
Describe the four root zones (from tip upward).
Root cap: Protects apical meristem, secretes mucigel.
Zone of cell division: Apical meristem produces new cells.
Zone of elongation: Cells lengthen, pushing root tip.
Zone of maturation: Cells differentiate (root hairs form).
What is the Casparian strip, and why is it important?
Waxy barrier in root endodermis.
Forces water/nutrients to pass through cell membranes (selective absorption).
Compare taproot vs. fibrous root systems.
Taproot: Single dominant root (e.g., carrots).
Fibrous: Many thin roots (e.g., grasses).
Label the leaf anatomy (cross-section).
Cuticle: Waxy layer (prevents water loss).
Epidermis: Protective outer layer.
Mesophyll:
Palisade: Tightly packed cells (photosynthesis).
Spongy: Air spaces (gas exchange).
Stomata: Pores regulated by guard cells.
How do guard cells regulate stomatal opening?
K+ uptake → water influx → turgor pressure → stomata open.
K+ loss → water efflux → stomata close (prevents dehydration).
What is leaf abscission, and why does it occur?
Seasonal shedding of leaves (deciduous plants).
Triggered by hormones (ethylene, ABA) to conserve water in winter.
Explain the cohesion-tension theory of water transport.
Transpiration (water loss from leaves) creates tension.
Cohesion (H-bonds between water molecules) pulls water upward through xylem.
What drives phloem translocation?
Pressure flow hypothesis:
Sugars loaded into phloem (source → high pressure).
Water follows osmosis → fluid flows to sink (roots/fruits).
Sugars unloaded (pressure drops).
How do plants absorb nutrients from soil?
Active transport (ATP-driven) at root hairs.
Symbiosis with mycorrhizae (fungi) and nitrogen-fixing bacteria.
Define tropisms and provide examples.
Directional growth responses:
Phototropism (light; auxin redistribution).
Gravitropism (gravity; statoliths in root cap).
Thigmotropism (touch; e.g., vines wrapping).
What role do plant hormones play in responses?
Auxins: Cell elongation, apical dominance.
Cytokinins: Cell division, delay senescence.
Ethylene: Fruit ripening, leaf abscission.
Abscisic acid (ABA): Stress response (close stomata).
How do plants respond to herbivory?
Chemical defenses: Toxins (e.g., alkaloids).
Physical defenses: Thorns, trichomes.
Systemic signaling: Jasmonic acid triggers defense genes.
Compare osmosis, diffusion, and active transport.
Osmosis: Water moves across membrane (high → low water potential).
Diffusion: Passive solute movement (high → low concentration).
Active transport: ATP-driven solute movement (low → high concentration).
What is guttation, and how does it differ from transpiration?
Guttation: Water exudes from leaf edges (via hydathodes) at night (root pressure).
Transpiration: Daytime water loss via stomata (evaporation).
