Plant Biology: Structure, Physiology, Nutrition, and Reproduction

A comprehensive vocabulary review deck covering plant anatomy, physiology, nutrient transport, hormones, evolutionary groups, and pollination syndromes.

Photoautotrophs

Organisms that synthesize their own food using light energy; the classification of most plants.

CHONPS

An acronym standing for the essential plant macronutrients: Carbon, Hydrogen, Oxygen, Nitrogen, Phosphorus, and Sulfur.

Essential Plant Macronutrients (Examples)

Three macronutrients essential for plants: Carbon, Nitrogen, and Phosphorus.

Plant Micronutrients

Nutrients required by plants in trace amounts, including Fe, Mn, B, Mo, Cu, Zn, Cl, Ni, Co, Na, and Si.

Nitrogen (Plant Role)

An essential plant nutrient needed in proteins, nucleic acids, and some vitamins.

Organic Material (in Soil)

A soil component that helps release nutrients quickly and improves nutrient-holding capacity.

Loam

A balanced mixture of sand, silt, and clay that holds nutrients and water but drains adequately.

Root Systems (Three Types)

The three main types of root systems found in plants: taproots, fibrous roots, and adventitious roots.

Root Hairs

Extensions on root epidermal cells that increase surface area for water and nutrient uptake.

Casparian Strip

A waterproof band in root endodermis that helps prevent unwanted materials from entering vascular tissue.

Shoot System

The above-ground plant structure that supports the plant and facilitates photosynthesis and reproduction.

Meristematic Tissue

Undifferentiated plant tissue that divides continuously to allow growth.

Primary vs. Secondary Growth

Primary growth increases length in plants, whereas secondary growth increases girth.

Stomata

Microscopic openings on leaves that regulate gas exchange.

Guard Cells

Specialized epidermal cells that control stomatal opening by regulating ion movement and water entry, causing turgidity.

Transpiration

The loss of water vapor from plant surfaces, occurring primarily through stomata.

Xylem Cargo

Water and dissolved minerals transported through xylem tissue.

Phloem Cargo

Sugars and other organic compounds transported through phloem tissue.

Xylem Transport Drivers

Transpiration pull and cohesion-tension, which drive the upward movement of water in xylem.

Diffusion vs. Facilitated Diffusion

Diffusion moves particles down a concentration gradient, while facilitated diffusion uses membrane proteins to transport particles.

Turgor Pressure

Hydrostatic pressure inside plant cells that helps maintain cell structure and prevents wilting.

Water Movement Routes

The three pathways for water movement in plant tissues: transmembrane, symplastic, and apoplastic routes.

Cohesion (in Water Transport)

The attractive force between water molecules that keeps the continuous water column connected in the xylem.

Humidity Effect on Transpiration

The environmental interaction in which transpiration increases when air humidity is low.

Trichomes

Hair-like outgrowths on leaves that can deter herbivores and reduce water loss.

Palisade Mesophyll

Densely packed leaf tissue involved in photosynthesis that contains chloroplasts.

Parenchyma vs. Sclerenchyma

Parenchyma is living plant tissue involved in storage and photosynthesis, while sclerenchyma is dead at maturity and provides mechanical support.

Mycorrhizae

Symbiotic associations between fungi and plant roots that exchange fungal-acquired nutrients for plant carbohydrates.

Transpiration Diffusion Process

The process where water vapor diffuses from leaves, occurring more readily when air humidity is low.

Transpirational Water Loss Percentage

About $97\%$ of water entering plant roots is lost through transpiration.

Phloem Pressure-Flow Sequence

The transport mechanism where sucrose is loaded into companion cells/sieve tubes at the source, lowering solute potential, causing water to enter from xylem by osmosis, increasing pressure, and driving sap toward the sink where sugar is unloaded.

Source vs. Sink

A source is where sugar is made or released (often leaves), while a sink is where sugar is used or stored (roots, growing tissues, fruits, stems).

Sugar Unloading Methods

The release of sugar at plant sinks, which can occur by diffusion or active transport depending on concentration.

Homeostasis (in Plants)

The maintenance of stable internal conditions despite external changes, often requiring a higher energy cost.

Plant Hormones

Chemical signals that regulate growth and development in plants.

Auxin

A plant hormone that promotes cell elongation, phototropism, gravitropism, apical dominance, fruit development, vascular differentiation, and adventitious roots.

Cytokinin

A plant hormone that promotes cell division and growth, works with auxin, and delays senescence.

Gibberellin

A plant hormone that promotes shoot elongation, leaf growth, germination, and release from dormancy while inhibiting senescence.

Abscisic Acid (ABA)

A plant hormone that acts as a stress signal, rising with low water availability, closing stomata, promoting dormancy, and inhibiting elongation and germination.

Ethylene

A volatile gas hormone in plants that promotes fruit ripening, flower wilting, and leaf abscission.

Phototropism

The directional growth response where auxin accumulates on the shaded side of a shoot exposed to light from one side, causing those cells to elongate more and bend the shoot toward the light.

Evolutionary Innovations of Plants

Key evolutionary developments in plants, including protected embryos, alternation of generations, vascular tissue, seeds and pollen, and flowers and fruits.

Bryophytes

Nonvascular plants (mosses, liverworts, hornworts) that require water for reproduction and have a dominant gametophyte stage.

Seedless Vascular Plants

Plants (ferns and allies) that have vascular tissue and true roots, stems, and leaves but produce no seeds, possessing flagellated sperm requiring water for reproduction.

Gymnosperms

Vascular seed plants with naked seeds, including conifers, cycads, ginkgo, and gnetophytes, characterized by a dominant sporophyte stage.

Angiosperms

Flowering plants with vascular tissue, a dominant sporophyte stage, seeds enclosed in fruit, and double fertilization.

Monocots vs. Dicots

Monocots usually have flower parts in threes, parallel veins, and scattered vascular bundles; dicots have flower parts in fours/fives, net-like veins, and vascular bundles in a ring.

Alternation of Generations

A reproductive plant cycle involving a diploid sporophyte producing haploid spores by meiosis, which grow into haploid gametophytes producing sperm and eggs, leading to fertilization and formation of a diploid zygote.

Flower Parts

Floral organs consisting of sepal (protects bud), petal (attracts pollinators), stamen (male part: anther + filament), and carpel/pistil (female part: stigma + style + ovary).

Pollination vs. Fertilization

Pollination occurs when pollen reaches the stigma, whereas fertilization occurs when sperm fuses with the egg or central cell.

Double Fertilization

An angiosperm process where one sperm fertilizes the egg to form a diploid zygote, while another sperm fuses with polar nuclei to form a triploid endosperm.

Wind-Pollinated Flowers

Flowers that are usually dull, lack scent, often lack petals, and produce abundant lightweight pollen.

Beetle-Pollinated Flowers

Flowers that are bowl-shaped with a fruity/spicy smell and many stamens, providing pollen or food bodies.

Hummingbird-Attracting Flowers

Flowers featuring narrow tubes, often colored red, orange, or yellow, lacking scent, and which may lack a landing platform.

Bee-Attracting Flowers

Flowers that are open bowls or broad tubes, often with nectar guides and a sweet scent.

Bat-Attracting Flowers

Flowers that are often large and sturdy, pale, green, or purple in color, with a sweet or musty scent, typically blooming at night.