Plant Structure, Embryogenesis & Seed Biology – BIOEB204 Lecture 2

Vocabulary flashcards summarising key terms from the lecture on plant structure, embryogenesis, meristems, and seed biology.

Confocal Laser Scanning Microscope

A light microscope that scans specimens with lasers to collect optical slices, allowing sharp 3-D reconstructions of thick plant tissues.

Differential Interference Contrast (DIC) Microscope

A light microscope that uses polarized light and prisms to enhance contrast in live, transparent samples, producing pseudo-3-D images.

Embryogenesis (plant)

The series of orderly cell divisions and expansions that transform a zygote into a structured plant embryo with shoot and root poles.

Globular Stage

Early spherical phase of embryogenesis where the apical and basal cells divide to establish basic embryo regions.

Heart Stage

Embryo phase in eudicots when two cotyledon primordia give the embryo a heart-shaped outline.

Torpedo Stage

Elongated embryo phase showing a clear root–shoot axis and emerging vascular (cambial) strands.

Maturation Stage

Final embryogenesis phase in which the embryo dehydrates, folds, and is packaged as a dormant seed.

Zygote

The single diploid cell produced by fertilisation that initiates sporophytic embryogenesis.

Apical Cell

The upper daughter cell of the first zygotic division; it forms most of the embryo proper.

Basal Cell

Lower daughter cell of the zygote; divides anticlinally to form the embryonic suspensor or stalk.

Anticlinal Division

Cell division perpendicular to the surface wall, increasing cell rows without thickening the tissue layer.

Radial Pattern

Concentric arrangement of tissue layers (dermal, ground, vascular) from the centre to the surface of the embryo or stem.

Axial Pattern

Longitudinal organisation of plant body from shoot apex through hypocotyl to root tip.

Meristem

A region of small, isodiametric, perpetually embryonic cells capable of continuous division to generate new tissues.

Initials (meristem)

Stem-cell-like meristematic cells that retain the ability to divide indefinitely.

Derivatives

Daughter cells of initials that divide and then differentiate into specific primary tissues.

Apical Meristem

Meristem located at the tips of shoots or roots responsible for primary (length) growth.

Shoot Apical Meristem (SAM)

The apical meristem at the shoot tip that produces leaves, stems, and flowers.

Root Apical Meristem (RAM)

The apical meristem at the root tip that generates root tissues and root cap.

Primary Meristems

Zones just beneath apical meristems (protoderm, ground meristem, procambium) that give rise to primary tissue systems.

Protoderm

Primary meristem layer that differentiates into the dermal (epidermal) tissue system.

Ground Meristem

Primary meristem that forms ground tissues such as cortex and pith.

Procambium

Primary meristem strand that develops into primary vascular tissues (xylem and phloem).

Secondary Meristem

Meristem that forms later from dedifferentiated cells to produce secondary growth (e.g., vascular cambium, cork cambium).

Vascular Cambium

A cylindrical secondary meristem that adds secondary xylem (wood) inward and secondary phloem outward, thickening stems and roots.

Pericycle

Outer layer of the vascular cylinder in roots that can act as a secondary meristem initiating lateral roots.

Indeterminate Growth

Growth pattern in which an organism continues to produce new organs and tissues throughout life via meristems.

Determinate Growth

Growth that stops once an organ (e.g., leaf, flower) reaches its genetically programmed size and form.

Metamer (Phytomere)

A repeating shoot unit consisting of a node, leaf, axillary bud, and internode.

Node

Point on a stem where a leaf and its axillary bud are attached.

Internode

Stem segment between two successive nodes.

Axillary Bud

Dormant or active shoot apex located in the leaf axil that can grow into a branch or flower.

Tap Root System

Root architecture with one dominant primary root and smaller lateral branches; typical of many dicots.

Fibrous Root System

Root architecture composed of many similarly sized roots, often arising adventitiously; common in grasses.

Adventitious Root

Root that originates from non-root tissue, such as stems or leaves.

Cotyledon

Seed leaf; embryonic organ that stores or absorbs nutrients for the germinating seedling.

Endosperm

Triploid nutritive tissue formed by double fertilisation in angiosperms; food reserve for the embryo.

Scutellum

Specialised single cotyledon of grasses that absorbs nutrients from the endosperm during germination.

Eudicot

A major clade of angiosperms usually possessing two cotyledons and net-veined leaves.

Monocot

Angiosperm group characterised by a single cotyledon, parallel-veined leaves, and scattered vascular bundles.

Epigial Germination

Germination type in which the cotyledons are pushed above the soil surface by hypocotyl elongation.

Hypogial Germination

Germination type where cotyledons remain below the soil as the epicotyl elongates.

Coleoptile

Protective sheath surrounding the emerging shoot in grass (monocot) seedlings.

Coleorhiza

Protective sheath surrounding the emerging radicle (root) in grass seeds.

Orthodox Seed

Seed type that tolerates dehydration, enters dormancy, and can be long-term stored dry (e.g., melon).

Recalcitrant Seed

Seed type that cannot survive drying, lacks prolonged dormancy, and must germinate quickly (e.g., avocado).

Seed Dormancy

Physiological or physical state preventing germination under otherwise favourable conditions.

Seed Bank

Natural or artificial store of viable seeds remaining in soil or conserved ex situ for future germination.

Asexual Reproduction (plant)

Formation of new plants without meiosis or fusion of gametes, e.g., via stolons, rhizomes, or cuttings.

Alternation of Generations

Plant life cycle in which multicellular haploid (gametophyte) and diploid (sporophyte) generations alternate.