achene Small, dry, indehiscent fruit containing a single seed.
adventitious root Root that develops from non-root tissue such as a stem.
allelopathy Production of biochemicals to inhibit the development and growth of neighbouring plants.
alternation of generations Life cycle comprising alternating haploid gametophyte and diploid sporophyte generations.
anther Pollen-producing part of the stamen of a flower.
antheridium (pl. antheridia) Organ that produces and holds male sperm cells in bryophytes, fern allies and ferns.
antheridiophore Upright structure in some bryophytes that bears antheridia.
apomixis (adj. apomictic) Asexual reproduction involving the formation of an embryo without the formation of eggs or sperm. The resultant offspring is a clone. Also known as agamospermy.
archegonium (pl. archegonia) Organ producing and holding female egg cells in bryophytes, fern allies, ferns and some gymnosperms.
aril Outer seed appendage, usually fleshy and brightly coloured.
bract Modified leaf, often growing below a flower or inflorescence.
cambium Thin layer of tissue between the xylem and phloem whose cells actively divide to produce secondary growth.
capitulum Composite flowerhead in members of the daisy family (Asteraceae).
carpel Female reproductive organ of a flower that encloses the ovules.
caryopsis Achene whose seed coat is joined to the ovary wall, as in grasses.
caudicle In orchids, the thread attaching pollinia to the flower column.
chloroplast Specialized chlorophyll-containing plant organelle responsible for photosynthesis.
cladode Modified stem that resembles and functions like a leaf, carrying out photosynthesis.
collenchyma cells Specialized parenchyma cells with selectively thickened cellulose walls, providing flexible support in stems (cf. sclerenchyma cells).
corm Swollen underground stem base that acts as a storage organ.
cotyledon Embryonic leaf in angiosperms, usually the first leaf present on germination. Monocotyledons have one cotyledon, while dicotyledons have two.
cyme (adj. cymose) Inflorescence whose main axis terminates in a single flower that blooms before those on the lateral stems below.
dioecious Having male and female reproductive organs on separate plants (cf. monoecious).
diploid Having two complete sets of chromosomes, one inherited from the sperm cell and the other from the egg cell (cf. haploid).
drupe Fleshy fruit with a thin skin and single hard stone enclosing a seed, e.g. a plum. Drupelets are small drupes, as seen in aggregate fruits, e.g. raspberries.
early wood Wood produced at the start of the growing season, characterized by large cells with thin walls (cf. latewood).
elaiosome Fat- or protein-rich fleshy seed appendage, often used to attract ants for seed dispersal.
endodermis Single cell layer surrounding the inner vascular tissue in roots.
endosperm Food reserve inside a seed that nourishes the embryo.
epiphyte Non-parasitic plant that grows on another for support.
gamete Mature haploid sex cell of an organism, either the female egg cell or male sperm cell. Gametes of the opposite sex unite during sexual fertilization to form a diploid offspring.
gametophyte Haploid, gamete-producing generation in the life cycle of a land plant (cf. sporophyte).
gemma (pl. gemmae) Cluster of cells that can separate from a parent plant and produce new individuals in a form of asexual reproduction.
genome Complete set of an organism’s genetic information, including its DNA and genes.
haploid Having a single set of chromosomes, half the diploid number (cf. diploid).
haustorium (pl. haustoria) Specialized modified stem or root of a parasitic plant that penetrates the host plant to extract nutrients.
hypanthium Usually cup-like flower structure that bears the sepals, petals and stamens, e.g. in rose family (Rosaceae) members.
hypocotyl Part of the plant embryo above the radicle and below the cotyledons.
indusium Tissue that covers and protects the sorus of a fern.
inflorescence Flowering stem of a plant with more than one flower, classified by the arrangement of flowers.
integument Tough jacket-like coat of a seed.
krummholz Vegetation comprising trees that are stunted through exposure to high winds in extreme subalpine and subarctic environments.
lamina (pl. laminae) Leaf blade, where the majority of photosynthesis takes place.
latewood Wood produced later in the growing season, characterized by small cells and thicker walls (cf. early wood).
lignin Decay-resistant cell wall polymer that forms wood and provides support.
lignotuber Swelling at the stem base containing buds and food reserves from which new growth arises when the plant is damaged, e.g. by fire.
meiosis Process by which diploid cells divide to produce four haploid cells. It involves two cell divisions, during the first of which there is an exchange between chromosomes of maternal and paternal genetic material.
meristem Area of undifferentiated tissue where active cell division causes growth to occur. Apical meristem is located at root and shoot tips.
mesophyll Leaf tissue, comprising palisade mesophyll and spongy mesophyll cells.
micropyle Narrow channel in the ovule of a seed-bearing plant though which the pollen tube gains entry.
monoecious Having male and female reproductive organs on the same plant (cf. dioecious).
mycorrhiza (pl. mycorrhizae) Fungus that forms a symbiotic relationship with a plant through its roots. In ectomycorrhizae the fungal hyphae do not penetrate the plant’s roots, whereas in endomycorrhizae the hyphae enter the root cells.
nectary Organ that produces nectar as a reward for pollinators.
nucellus Central part of the ovule, containing the embryo sac.
palisade mesophyll Upper layer of the mesophyll, comprising elongated cells whose chloroplasts absorb the majority of sunlight for photosynthesis.
panicle Many-branched inflorescence in which the lower flowers are oldest.
paraphyletic Group of organisms that contains a common ancestor and some but not all of its descendants.
parasite Organism that lives in or on another and gains a benefit at a cost to the host.
parenchyma cells Thin-walled cells that form the ground tissue of a plant.
petal Flat, coloured, non-fertile structure outside the reproductive parts of a flower.
petiole the stalk of the leaf, which connects the leaf blade or lamina to the stem.
phloem Living vascular tissue that transports sugars around a plant (cf. xylem).
photosynthesis Process by which green plants use energy from sunlight to convert carbon dioxide and water into sugars and oxygen.
phyllode Modified flattened petiole that functions as a leaf.
pistil Female part of a flower, comprising the stigma, style and ovary.
pit membrane Relatively thin membrane across the centre of a pit in the cell wall of a tracheid, through which water passes.
plumule First shoot produced on germination, arising above the hypocotyl and bearing the cotyledon(s).
pneumatophore Aerial root of some waterlogged plants, e.g. mangroves, through which gas exchange occurs.
pollen Microscopic male gametophytes of seed plants produced by male cones and flowers, containing the male sex cells.
pollinium (pl. pollinia) Cluster of numerous coherent pollen grains dispersed as a unit in some flowers, e.g. orchids.
pome Fruit comprising a fused hypanthium surrounding a central seed-containing core, e.g. an apple.
raceme (adj. racemose) Simple inflorescence with individual flowers borne on short stems off a central main axis.
rachis (pl. rachides) The main axis of a compound structure, e.g. central axis of a fern frond or elongated axis of an inflorescence.
radicle Part of the plant embryo that develops into the first root on germination.
receptacle Enlarged tip of the stem that bears the flower organs.
rhizobium (pl. rhizobia) Nitrogen-fixing bacterium that colonizes cells within the root nodules of some plants, e.g. legumes (Fabaceae).
rhizoid Thread-like unicellular protuberance on the underside of a bryophyte gametophyte that acts like a root.
rhizome Root-like stem that grows horizontally underground.
samara Simple dry, hard fruit with one or more wings to aid dispersal.
sclerenchyma cells Specialized parenchyma cells with lignified secondary walls, providing rigid support in stems (cf. collenchyma cells).
seed bank Seed-storage facility established as a means of preserving plant diversity.
self-fertilization In which the male and female sex cells of a single individual fuse. No new genetic material is introduced but many offspring can be produced.
sepal Usually green, leaf-like structure below the petals of a flower.
serotiny (adj. serotinous) Release of seeds in response to an environmental trigger, e.g. fire.
sorus (pl. sori) Cluster of sporangia in a fern.
spathe Large bract protecting the flower spike in some plants, e.g. arum family (Araceae).
sporangium (pl. sporangia) Structure in bryophytes, fern allies and ferns in which spores are formed.
sporophyll Leaf in spore-bearing plants that carries sporangia.
sporophyte Diploid, asexual generation in the life cycle of a land plant (cf. gametophyte).
stamen Male reproductive structure of a flowering plant, comprising the anther and stalk-like filament.
stolon Stem growing horizontally across the ground surface that produces roots and branches – and hence new plants – at specialized nodes. Also called a runner.
stoma (pl. stomata) Microscopic opening, usually on the underside of a leaf, through which gas exchange occurs.
strobilus (pl. strobili) Cone-like structure in lycophytes and horsetails that bears sporophylls; also refers to cones in gymnosperms.
style Part of the pistil between the ovary and stigma.
suberin Waterproof wax-like substance that impregnates cork cell walls.
syconium (pl. syconia) Hollow receptacle whose interior contains many tiny flowers, e.g. a fig.
syncarp (adj. syncarpous) Fruit that develops from a female organ with fused carpels.
tepal Outermost organ of a flower in which the sepals and petals are undifferentiated.
thallose Having a flattened structure with no differentiation into leaves or stems.
thermogenesis Heat production within an organism, e.g. in flowers.
thigmonasty Movement of a plant organ in response to touch. Also called seismonasty.
torus-margo pit Specialized cell wall pit in a conifer tracheid that acts like a valve to regulate water flow.
trichome Hair-like structure in some plants, whose structure and function varies widely.
tracheid Rigid, tubular xylem cell through which water is transported.
xylem Vascular tissue with lignified cell walls comprising tracheids or vessels that transports water from the roots upwards to the rest of the plant.
zoospore Haploid dispersal cell of an alga, which uses one or more flagellae to move.
zygomorphic Of a flower, bilaterally symmetrical, able to be cut into two equal halves in only one way.
zygote Diploid cell produced following the fertilization of a haploid egg cell by a haploid sperm cell.