Plant Biology: Mitosis, Meiosis, Classification, Species Concepts, and Leaf Anatomy

Vocabulary practice flashcards covering plant cell division (mitosis and meiosis stages, ploidy concepts), plant life cycles (alternation of generations), taxonomic classification rules, species concepts, and internal and external leaf anatomy and modifications.

Cell Cycle

The recurring loop of growth and division in cells that are living at maturity (such as parenchyma, but not tracheids or vessel elements), consisting of interphase and M phase.

Mitosis

The division of the cell nucleus that replicates one parent cell into two genetically identical daughter cells, primarily occurring in meristematic regions for growth and repair.

$G_1$ Phase (Gap 1)

The initial growth stage of interphase where a newly divided half-sized cell enlarges to normal size and conducts its specialized everyday life functions.

$S$ Phase (Synthesis)

The portion of interphase during which the cell duplicates its single strands of DNA into pairs of identical sister chromatids in preparation for cell division.

$G_2$ Phase (Gap 2)

The second growth stage of interphase where the cell enlarges further and duplicates cytoplasmic organelles (such as chloroplasts and mitochondria) prior to M phase.

Sister Chromatid

One of two identical strands of DNA produced during replication that remain joined together at the centromere until separated during anaphase.

Centromere

The specific region or connection point where two sister chromatids are held together prior to their separation.

Prophase (Mitosis)

The first phase of mitosis, characterized by the condensation of chromatin into visible chromosomes, the breakdown of the nuclear envelope, and the attachment of spindle fibers.

Metaphase (Mitosis)

The stage of mitosis where chromosomes align along the spindle equator in the center of the cell.

Anaphase (Mitosis)

The mitotic phase in which spindle fibers pull sister chromatids apart at the centromere toward opposite poles of the dividing cell.

Telophase (Mitosis)

The final stage of mitosis during which separated chromosomes reach opposite poles, decondense, nuclear envelopes reform around each set, and a cell plate begins to form.

Cell Plate

The developing structure in dividing plant cells that forms along the division plane to construct the middle lamella and primary cell walls between two new daughter cells.

Cytokinesis

The division of the cytoplasm and partitioning of organelles between daughter cells following mitosis, involving the completion of the cell wall.

Plasmodesmata

Microscopic cytoplasmic channels traversing plant cell walls, maintained during cytokinesis when portions of the endoplasmic reticulum obstruct cell plate formation.

Meiosis

A reduction division in which one diploid or polyploid cell undergoes two nuclear divisions to yield four genetically distinct daughter cells containing half the original genetic complement.

Ploidy

The number of complete sets of chromosomes or copies of each individual chromosome present within a cell.

Botanical Ploidy Notation ($x$ vs. $n$)

In plants, $x$ represents the base number of chromosome copies (e.g., $1x, 2x, 8x$), whereas $n$ designates cells derived from meiosis and $2n$ indicates cells created by fertilization.

Octoploid ($8x$)

An organism or cell possessing eight copies of each chromosome, such as commercial cultivated strawberries bred for enlarged fruit size.

Prophase I

The meiotic stage where homologous chromosomes condense, pair up, and undergo crossing over at chiasmata to exchange genetic material.

Chiasmata

X-shaped points of overlap where non-sister chromatids of homologous chromosomes cross over and swap segments during prophase I.

Tetrad

A four-part structure consisting of two paired homologous chromosomes (four distinct chromatids) aligned together during meiosis I.

Anaphase I

The stage of meiosis I in which homologous chromosome pairs separate and move toward opposite poles, while sister chromatids remain joined at their centromeres.

Anaphase II

The stage of meiosis II in which centromeres split and sister chromatids are pulled apart to opposite ends of the cell.

Alternation of Generations

The plant life cycle characterized by alternating multicellular haploid ($x$) gametophyte and multicellular diploid ($2x$) sporophyte generations.

Gametophyte

The haploid ($x$) multicellular generation in plants that produces gametes (eggs and sperm) via mitosis.

Sporophyte

The diploid ($2x$) multicellular plant generation that develops from a zygote and contains sporocytes that produce haploid spores through meiosis.

Spore

A haploid ($x$) reproductive cell generated by meiosis in a sporophyte, capable of germinating into a genetically distinct gametophyte plant without fertilization.

International Code of Botanical Nomenclature

The official document governing the rules for naming species of algae, fungi, and plants, authorized by the International Botanical Congress.

Type Specimen

The original preserved specimen upon which the published scientific description and diagnosis of a newly named species is formally based.

Cultivar

A cultivated plant variety created or selected by humans via selective breeding or hybridization, designated by a genus and a capitalized common name in quotes.

Cultivar Group

A formal botanical grouping between genus and species used to assemble cultivars sharing defined traits such as flower color, growth habit, or plant height.

Morphological Species Concept

A species concept that classifies and identifies organisms based primarily on shared structural and anatomical physical appearances.

Phenotypic Plasticity

The ability of an individual genotype to produce different phenotypic expressions (such as leaf shape or flower stem height) in response to varying environmental conditions.

Biological Species Concept

A species concept that defines a species as groups of interbreeding natural populations that can successfully reproduce with one another.

Cuticle

A waxy, fatty waterproofing layer covering the outer surface of a leaf's epidermis to prevent desiccation.

Palisade Mesophyll

A densely packed layer of elongated, cylindrical parenchyma cells located directly beneath the upper epidermis of eudicot leaves, specialized for photosynthesis.

Spongy Mesophyll

A loosely organized layer of photosynthetic parenchyma cells located below the palisade mesophyll, characterized by extensive air spaces that facilitate gas exchange.

Bulliform Cells

Enlarged, pressurized epidermal cells found in monocot leaves that deflate upon water stress, causing the leaf blade to roll closed to minimize surface area and transpiration.

Vein (Leaf)

A vascular bundle within a leaf composed of xylem, phloem, and surrounding bundle sheath cells that conducts water, minerals, and carbohydrates.

Shade Leaves

Leaves adapted to low-light conditions that are thinner in cross-section, broader in surface area, and paler due to reduced chlorophyll concentrations.

Arid Region Leaves

Thick, leathery leaves with reduced surface area, fewer stomata, and vertical or east-west orientations designed to limit direct solar exposure and water loss.

Aquatic Plant Leaves

Leaves of submerged or floating plants that lack distinct veins and differentiation between epidermal layers, featuring enlarged air chambers in aerenchyma to provide buoyancy.

Tendril

A modified, thread-like leaf or stem adapted to coil around surrounding supports to aid climbing plants.

Spine

A sharp, defensive modified leaf with non-living sclerenchyma tissue at maturity, positioned directly subtending an axillary bud.

Thorn

A rigid, sharp defensive structure that represents a modified stem developing directly from an axillary bud.

Prickle

A sharp defensive outgrowth derived solely from epidermal tissue that lacks internal vascular connections and easily snaps off.

Storage Leaves

Thickened, fleshy leaves found in succulents specialized for retaining large reservoirs of water.

Flower Pot Leaf

A hollow, pouch-like modified leaf produced by epiphytic plants like Dischidia that shelters ant colonies, collects soil brought by ants, and absorbs nutrients via internal adventitious roots.

Window Leaves

Cone-like, mostly buried succulent leaves with transparent apical tips that transmit sunlight into an internal cavity lined with photosynthetic palisade mesophyll.

Reproductive Leaves

Leaves that produce miniature plantlets along their margins to facilitate asexual vegetative propagation, as seen in mother of thousands.

Bract

A specialized, often brightly colored floral leaf located below a flower or inflorescence that assumes the pollinator-attracting role of petals.

Pitcher Plant Leaf

A vase-shaped carnivorous leaf with slippery waxy margins and downward-pointing hairs that traps and drowns insects in digestive enzymes to acquire nitrogen.

Sundew Leaf

A carnivorous leaf covered in glandular trichomes tipped with sticky digestive droplets that curl over captured insects upon mechanical stimulation.

Venus Flytrap Leaf

A hinged, bivalved carnivorous leaf that snaps shut via rapid turgor changes when prey contacts its sensory trigger hairs, trapping the insect for enzymatic digestion.

Bladderwort Trap

An underwater suction bladder on an aquatic carnivorous plant that triggers open in roughly 100 milliseconds upon sensory hair contact to draw in small invertebrates.

Autumnal Color Change

The seasonal degradation and loss of green chlorophyll in response to declining sunlight and temperature, unmasking underlying yellow, orange, and red accessory pigments.

Abscission

The controlled physiological process of shedding plant leaves or organs to conserve water, reduce metabolic maintenance costs during dormancy, or prevent snow-induced limb damage.

Abscission Zone

A specialized region at the base of a leaf petiole where middle lamella pectin is enzymatically dissolved and a suberin-rich protective layer forms a scar before the leaf detaches.