Plant Science exam 3

What four functions does soil provide?

Temperature/moisture regulation; anchorage; microbial communities; mineral nutrients.

Essential vs. beneficial mineral elements?

Essential: required to complete life cycle. Beneficial: improve growth but not strictly required.

Macronutrients vs. micronutrients?

Macronutrients: needed in large amounts (>0.1% dry mass). Micronutrients: needed in small amounts (<0.01%).

How do roots absorb minerals?

As dissolved cations (+) and anions (−) in soil water.

Give examples of cations and anions.

Cations: K+, Ca2+, Mg2+. Anions: Cl−, NO3−, phosphate.

How do proton pumps aid nutrient uptake?

ATP-driven H+ export creates an electrochemical gradient that drives mineral transport.

What is cation exchange?

Root-released H+ displaces nutrient cations from negatively charged soil particles.

Why is anion absorption challenging?

Negative cell interiors oppose entry; negatively charged soil particles poorly retain anions.

What do ion channels do?

Selectively allow particular ions to cross membranes, often down electrochemical gradients.

What replenishes nutrients near roots?

Bulk water flow, diffusion toward depleted root zones, and root growth into fresh soil.

What is potassium's role?

Stomatal opening/closing and enzyme activation.

What is nitrogen's role?

Proteins, nucleic acids, and chlorophyll.

What is phosphorus's role?

ATP, nucleic acids, and phospholipids.

What is sulfur's role?

Sulfur-containing amino acids and proteins.

What is calcium's role?

Middle lamella and cell signaling.

What is magnesium's role?

Chlorophyll component and enzyme cofactor.

What do manganese, copper, and zinc do?

Primarily function as enzyme cofactors.

What do chloride, boron, and cobalt do?

Cl: stomatal regulation; B: cell walls/development; Co: benefits some nitrogen-fixing microorganisms.

What are nutrient deficiency symptoms?

Stunted growth, chlorosis (yellowing), and necrosis (tissue death).

What is the Haber–Bosch process?

Industrial ammonia synthesis used for nitrogen fertilizers.

Compare sand, silt, and clay.

Sand: coarse/fast drainage; silt: intermediate; clay: tiny particles, high water/ion retention.

What is loam?

A balanced soil mixture of sand, silt, and clay.

Organic soils vs. mineral soils?

Organic: accumulated organic matter; mineral: mainly weathered rock.

What are O, A, B, C soil horizons?

O: organic debris; A: topsoil; B: accumulated minerals/clay; C: weathered parent material.

Young vs. mature soils and soil pH?

Young: often mineral-rich; mature: more leached; pH affects nutrient availability/decomposition (many plants favor 5.5–6.5).

What is the overall photosynthesis equation?

6CO2 + 6H2O + light → C6H12O6 + 6O2.

What did van Niel demonstrate?

Photosynthetic O2 comes from water, not CO2; sulfur bacteria use H2S instead of water.

What did Engelmann demonstrate?

Red and blue light caused greatest oxygen production, shown by aerobic bacterial clustering.

What did Blackman demonstrate?

Low light: little temperature effect; sufficient light/CO2: temperature affects photosynthesis.

Light-dependent vs. light-independent reactions?

Light reactions produce ATP, NADPH, O2; Calvin cycle uses ATP/NADPH to fix CO2.

Where do photosynthesis stages occur?

Light reactions: thylakoid membranes; Calvin cycle: stroma.

Thylakoids, grana, and lamellae?

Thylakoids: membrane sacs; grana: stacks; lamellae: membranes connecting stacks.

Stroma vs. lumen?

Stroma: fluid surrounding thylakoids; lumen: interior space accumulating H+.

Light as wave vs. particle?

Wave: wavelength; particle: photon. Shorter wavelength means higher photon energy.

Chlorophyll a vs. chlorophyll b?

Chlorophyll a: reaction-center pigment; b: accessory pigment broadening absorption.

What are carotenoids?

Accessory/protective pigments including carotenes and xanthophylls.

How does light energy reach the reaction center?

Antenna pigments transfer excitation energy to reaction-center chlorophyll, which transfers an electron.

Compare PSII and PSI.

PSII/P680 splits water and supports proton gradient; PSI/P700 supplies electrons for NADPH.

What is photolysis?

Splitting water to replace PSII electrons; produces O2 and H+.

What is linear electron flow?

H2O → PSII → electron transport chain → PSI → NADPH.

How does electron transport support ATP synthesis?

It builds an H+ gradient across the thylakoid membrane.

What is photophosphorylation?

ATP synthesis via H+ flow from lumen to stroma through ATP synthase.

Products of light-dependent reactions?

ATP, NADPH, and O2.

What is the Calvin cycle?

ATP/NADPH-powered fixation of CO2 into organic carbohydrates.

What happens in C3 photosynthesis?

Rubisco fixes CO2 to RuBP, forming two three-carbon PGA molecules.

What is Rubisco?

CO2-fixing Calvin-cycle enzyme that can also react with O2.

What is photorespiration?

Rubisco binds O2 instead of CO2, wasting fixed carbon.

What happens in C4 photosynthesis?

PEP initially fixes CO2 into a four-carbon compound; CO2 concentrates in bundle-sheath cells.

What happens in CAM photosynthesis?

Stomata open at night; CO2 stored as malic acid and released by day.

Compare C3, C4, and CAM.

C3: direct CO2 fixation; C4: spatial separation; CAM: temporal separation to conserve water.

Main stages of flowering-plant sexual reproduction?

Meiosis → pollination → fertilization → seed/fruit development → dispersal → germination.

Four floral whorls outside to inside?

Sepals, petals, stamens, carpels.

Perianth, calyx, and corolla?

Perianth = sepals + petals; calyx = all sepals; corolla = all petals.

Sepals, petals, and tepals?

Sepals protect buds; petals often attract pollinators; tepals lack clear sepal/petal distinction.

Androecium vs. gynoecium?

Androecium: male stamens; gynoecium: female carpels/pistils.

Parts of a stamen?

Anther makes pollen; filament supports anther.

Pollen sacs and microspores?

Pollen sacs house meiosis; haploid microspores develop into male gametophytes.

Pollen tube cell vs. generative cell?

Tube cell grows pollen tube; generative cell divides into two sperm.

Parts of a pistil?

Stigma receives pollen; style connects stigma and ovary; ovary houses ovules.

Simple vs. compound pistil?

Simple: one carpel; compound: multiple fused carpels.

What is placentation?

Arrangement of ovules within the ovary.

Parietal placentation?

Ovules attached to inner ovary walls.

Axile placentation?

Ovules attached to central axis in multilocular ovary.

Central placentation?

Ovules attached to a central column.

Marginal placentation?

Ovules attached along a carpel margin.

Integuments and micropyle?

Integuments protect ovule and form seed coat; micropyle is opening for pollen tube entry.

What are megaspores?

Haploid spores produced by meiosis that develop into female gametophytes.

What is the embryo sac?

Female gametophyte containing egg, synergids, central cell, and antipodals.

Egg cell vs. synergids?

Egg forms zygote; two synergids guide pollen tube.

Central cell vs. antipodals?

Central cell with polar nuclei helps form endosperm; three antipodals lie opposite egg apparatus.

What is double fertilization?

One sperm + egg → 2n zygote; other sperm + central cell → usually 3n endosperm.

Ovule vs. ovary after fertilization?

Ovule becomes seed; ovary becomes fruit.

What are floral apices?

Growing meristem regions that produce floral organs.

What is the ABC floral model?

A = sepals; A+B = petals; B+C = stamens; C = carpels.

Complete vs. incomplete flowers?

Complete: all four whorls; incomplete: missing at least one.

Perfect vs. imperfect flowers?

Perfect: stamens and carpels; imperfect: only one sex's reproductive structures.

Staminate vs. pistillate flowers?

Staminate: male/stamens; pistillate: female/pistils.

Connation vs. adnation?

Connation: fused parts of same whorl; adnation: fused parts of different whorls.

Superior vs. inferior ovary?

Superior: above attachment of floral parts; inferior: below their attachment.

What is a hypanthium?

Floral cup/tube formed by tissues around the ovary.

What is an inflorescence?

Cluster or arrangement of flowers on an axis.

What is a raceme?

Unbranched axis with stalked flowers.

What is a panicle?

Branched flower cluster.

What is a spike?

Unbranched axis with sessile flowers.

What is an umbel?

Flower stalks arise from approximately one point.

Cyme vs. compound inflorescence?

Cyme: terminal flower opens first; compound: consists of smaller inflorescence units.

What do flowers reward pollinators with?

Nectar (sugary water from nectaries) and pollen.

Biotic vs. abiotic pollination?

Biotic: animals; abiotic: wind or water.

Common wind-pollinated flower adaptations?

Small/inconspicuous, odorless, nectarless, with exposed reproductive parts.

Self-pollination vs. cross-pollination?

Self: same plant; cross: different plants of same species.

Advantages of self- vs. cross-pollination?

Self: reproductive assurance; cross: increased genetic recombination/variation.

What are fruit and pericarp?

Fruit: mature ovary containing seeds; pericarp: mature ovary wall.

Three layers of pericarp?

Exocarp: outer skin; mesocarp: middle layer; endocarp: inner layer, sometimes hardened.

What is a simple fruit?

Fruit from one ovary of one flower.

Dry vs. fleshy fruits?

Dry: dry pericarp at maturity; fleshy: soft/juicy pericarp.

Dehiscent vs. indehiscent fruits?

Dehiscent split to release seeds; indehiscent remain closed.

What is a legume?

Dry dehiscent fruit from one carpel, opening along two seams; bean pod.

What is a follicle?

Dry dehiscent fruit from one carpel, opening along one seam; magnolia.

What is a capsule?

Dry dehiscent fruit from compound ovary; poppy.

What is a silique?

Brassicaceae dry fruit with two valves separating from central partition.