Botany Lecture Notes: Plant Organs, Internal Structure, Photosynthesis, and Hormones

Vocabulary practice flashcards generated from the plant biology lecture on flowers, reproduction, internal leaf structure, stems, roots, photosynthesis, and hormones.

Pedicel

The stalk of a flower that is directly connected to the stem.

Receptacle

The region above the pedicel where the other floral parts attach.

Calyx

The collective term for sepals, which are lowermost floral appendages that enclose other flower parts as they mature.

Corolla

The group of petals in a flower responsible for attracting pollinators.

Perianth

The collective term referring to the petals and sepals combined.

Androecium

The male reproductive unit of a flower, constituted by stamens.

Gynoecium

The female reproductive unit of a flower, constituted by carpels.

Megagametophyte

The female reproductive gametophyte of a plant that develops from a megaspore, containing 7 cells and 8 nuclei.

Spathe

A large, brightly colored bract that encloses a spadix inflorescence.

Autogamy

A type of self-pollination in which pollen from the same flower fertilizes its own stigma.

Geitonogamy

A type of self-pollination where pollen moves to another flower on the same plant.

Cleistogamy

A type of self-pollination in which flowers never open and fertilization occurs automatically inside.

Double Fertilization

A process in angiosperms where one sperm fertilizes the egg to form a zygote, and a second sperm fertilizes two polar nuclei to form endosperm.

Albuminous Seeds vs. Non-Albuminous Seeds

Albuminous seeds retain a portion of endosperm at maturity to nourish the embryo post-germination, whereas non-albuminous seeds completely consume the endosperm prior to maturity and store food in cotyledons.

Pericarp

The entire fruit wall, which is composed of three layers: exocarp, mesocarp, and endocarp.

Epigeal Germination

Germination occurring above ground where cotyledons emerge from the soil driven by a long, downward-curving hypocotyl.

Hypogeal Germination

Germination occurring below ground where cotyledons remain inside the soil with a short hypocotyl and long epicotyl.

Sunken Stomata

Stomata recessed below the leaf surface that create pockets of still air to slow down water vapor escape, common in xerophytes.

Crypts

Specialized depressions in the leaf epidermis containing stomata and trichomes that trap moisture and reduce airflow.

Trichomes

Epidermal leaf hairs that provide shade, reduce transpiration, hinder herbivores, and trap fog or dew droplets.

Palisade Parenchyma

The main photosynthetic tissue located near the upper surface of most leaves, consisting of columnar cells with abundant chloroplasts.

Spongy Mesophyll

Loose, highly porous aerenchyma tissue located in the lower portion of a leaf that facilitates rapid diffusion of $CO_2$.

Dorsiventral Leaf

A horizontally oriented leaf blade with palisade parenchyma concentrated near the upper surface to optimize light capture from above.

Isobilateral Leaf

A vertically oriented leaf blade with palisade parenchyma present on both upper and lower surfaces.

Bundle Sheath

A fibrous jacket surrounding major leaf veins that provides structural strength and protection against herbivores.

Kranz Anatomy

A specialized leaf arrangement in $C_4$ plants characterized by prominent bundle sheaths and an absence of distinct palisade and spongy layers.

Photorespiration

A metabolic process in which RuBisCO binds to oxygen instead of carbon dioxide, consuming ATP without producing sugar.

Primary Stem Growth Differentiation

The process by which the subapical meristem gives rise to protoderm, provascular tissue, and ground meristem, forming the primary tissues of the stem.

Protoxylem vs. Metaxylem

Protoxylem differentiates early with small elements and annular/helical wall construction, whereas metaxylem differentiates later with larger elements and scalariform, reticulate, or pitted construction.

Phyllotaxy

The arrangement pattern of leaves on a stem, including alternate, opposite, whorled, spiral, decussate, and distichous arrangements.

Root Cap

A structure covering the root tip that protects the apical meristem, secretes lubricating mucigel, and contains statoliths for gravity sensing.

Statoliths

Dense starch grains inside root cap cells that settle to the bottom to mediate gravitropism.

Quiescent Center

A central zone of the root apical meristem with near-zero mitotic activity that serves as a damage-resistant cellular reservoir.

Velamen

A specialized root epidermis found in epiphytic plants that acts as a waterproof barrier to prevent internal moisture loss.

Mycorrhizae

Mutualistic associations between plant roots and fungi that increase nutrient and water absorption capabilities.

Auxins

Plant hormones produced at shoot tips that control apical dominance, cell elongation via acid growth, and tropic responses.

Cytokinins

Plant hormones that promote cell division, stimulate lateral bud development, and delay plant tissue aging.

Gibberellins

Plant hormones that promote stem elongation, trigger seed germination by activating $\alpha$-amylase, and break bud dormancy.

Abscisic Acid

A plant hormone that induces stomatal closure during drought stress and maintains dormancy in seeds and buds.

Ethylene

A gaseous plant hormone that promotes fruit ripening, leaf drop, and tissue softening.

Hormonal Interplay in Stress Responses

The pathway dynamic showing how drought and mineral nutrient deficiencies regulate auxin and cytokinin signaling to balance root and shoot development.

Thigmonasty

A non-directional plant movement triggered by direct mechanical contact or physical touch.

Nyctinasty

Rhythmic non-directional plant movements regulated by circadian clocks in response to daily light and dark cycles.

Tropic Movement vs. Nastic Movement

Tropic movements are directional, slow growth responses mediated by auxin, whereas nastic movements are non-directional, fast responses mediated by turgor and ion flux.

Phytochromes

Red and far-red light-sensing photoreceptor proteins that exist in $P_r$ and $P_{fr}$ forms to measure night length.

Florigen

The Flowering Locus T ($FT$) protein signal that travels through the phloem from leaves to the shoot apex to initiate flowering.