Glossary of Botanical Terms - A

A

abaxial

The side away from the axis, for instance the lower surface of a leaf.

abort

To abandon development of a structure of organ.

abscission

(adjective abscissile): A plant's normal shedding of an organ that is mature or aged, e.g. a ripe fruit or an old leaf.

acaulescent

An adjective descriptive of a plant that has no apparent stem, or at least none visible above ground. Examples include some species of Agave, Oxalis and Attalea.

accrescent

Increasing in size with age, such as a calyx that continues to grow after the corolla has fallen, for example in Physalis peruviana.

-aceae

The suffix added to the stem of a generic name to form the name of a family.

achene

A dry 1-seeded indehiscent fruit; e.g. members of the Ranunculaceae.

acicular

Slender or needle-shaped. See Leaf shape.

acropetal

Moving from roots to leaves, e.g. of molecular signals in plants.

acrophyll

The regular leaves of a mature plant, produced above the base; usually in contrast to bathyphyll.

acrostichoid

(describing a type of sorus) covering the entire abaxial surface of the frond, usually densely so, as in Elaphoglossum and Acrostichum.

actinomorphic

regular; radially symmetrical; may be bisected into similar halves in at least two planes. Generally applies to flowers in which the perianth segments within each whorl are alike in size and shape; compare irregular, regular, zygomorphic.

aculeate

Armed with prickles; e.g. the stem of a rose.

acuminate

Tapering gradually to a point.

acute

Sharply pointed; converging edges making an angle of less than 90°; compare obtuse.

adaxial

The side next to the axis; e.g. the upper surface of a leaf.

adnate

Fused to an organ of a different kind; e.g. a stamen fused to a petal; cf. connate.

adventitious

A structure produced in an abnormal position; e.g. an adventitious bud produced from a stem rather than from the axil of a leaf.

adventive

Introduced accidentally (usually referring to weeds).

aerial

Of the air; growing or borne above the surface of the ground.

aestivation

The arrangement of sepals and petals or their lobes in an unexpanded flower bud; cf. vernation arrangement of leaves in a bud.

affinis

With affinity to others, akin to; often used for a provisionally recognized but unnamed taxon considered close to that name, perhaps a hybrid or extreme variant.

aggregate fruit

A cluster of fruits formed from the free carpels of one flower, e.g. blackberry; cf. multiple fruit.

agricultural weed

see weed.

-ales

Suffix to the stem of a generic name or descriptive name to indicate that it applies to a taxon of the rank of order.

alien

Differing in nature, foreign; a plant introduced from elsewhere (exotic, introduced, non-native, non-indigenous).

alkaloid

Molecule with a nitrogenous base, many used as drugs; e.g. morphine, quinine, strychnine.

alternate

(as adjective) leaves or flowers borne singly at different levels along a stem includes spiralled parts; or (as verb) when something occurs between something else, for example stamens alternating with petals; compare opposite.

amphitropous

When the ovule is bent so that both ends are near each other; cf. anatropous, campylotropous, orthotropous.

amplexicaul

With the base dilated and clasping the stem, usually of leaves.

anastomosing

When veins are joined by cross-veins to form a network.

anatropous

When an ovule is inverted so that the micropyle faces the placenta (this is the most common ovule orientation in flowering plants); cf. amphitropous, campylotropous, orthotropous.

androdioecious

Of plants, having bisexual flowers and male flowers on separate individuals; cf. andromonoecious, polygamodioecious, polygamomonoecious, polygamous.

androecium

Male parts of flower; the stamens of a flower collectively; cf. gynoecium.

androgynophore

A stalk bearing both the androecium and gynoecium of a flower above the level of insertion of the perianth.

androgynous

With male and female flowers in the same inflorescence.

andromonoecious

Of plants, having bisexual and male flowers on the same individual; cf. andromonoecious, polygamodioecious, polygamomonoecious, polygamous.

Anemophily

Pollination by wind.

angiosperms

'flowering plants'; plants with developing seeds enclosed in an ovary.

annual

A plant that completes its life cycle and dies within one year.

anterior

Away from the axis; usually abaxial.

anther

Pollen-bearing part of the stamen.

anthesis

Time of flowering; the stage at which the pollen is released from the anthers inside the bud onto the pollen presenter, usually corresponding with flower opening.

antrorse

Directed towards or upwards, e.g. of hairs on a stem; cf. retrorse.

apetalous

Without petals.

apex

(plural apices) The tip; the point furthest from the point of attachment.

apiculate

(Usually referring to a leaf) terminating in a short sharp flexible point; less abrupt than mucronate.

apocarpous

Of a gynoecium consisting with one or more carpels which are free from one another (or almost so); e.g. Ranunculaceae, Dilleniaceae.

apomixis

Reproduction, where viable seed or spores are produced without fertilization. A plant produced in this way is an apomict.

appendage

A secondary part attached to the main structure; an external growth that seldom has any obvious function.

appressed

Pressed closely, but not fused; e.g. leaves against a stem.

aquatic

Plants whose natural habitat is water: living in or on water for all or a substantial part of the organism's life span, generally restricted to fresh or inland waters.

arachnoid

Cobwebby, from being covered with fine white hairs.

arborescent

Tree-like in growth or general appearance.

arboretum

(plural arboreta) A taxonomically arranged collection of trees.

archaeophyte

An non-native plant that has been present in a geographic area for some time; cf. neophyte.

areole

(from areola) A space between the threads of a net; e.g. that part of a leaf surface defined by each of the elements of a vein network; as with cacti, the area between the veinlets of a leaf or the region of a cactus bearing the flowers and/or spines.

aril

(adjective arillate): A membranous or fleshy appendage (formed by expansion of the funicle) which partly or wholly covers a seed; e.g. the fleshy outer layer of lychee fruit and as found in Sapindaceae.

aristate

With a stiff, bristle-like awn or tip.

article

A segment of a jointed stem or of a fruit with constrictions between the seeds; an organ part that separates easily from the rest of the organ at a joint or articulation.

articulate

Jointed; separating freely, leaving a clean scar; for example the fronds of certain ferns where they join the rhizome.

ascending

Spreading horizontally, then becoming erect.

asexual

Of reproduction that does not involve the gametes; i.e. vegetative reproduction.

attenuate

Narrowing gradually.

auricle

(adjective auriculate): Ear-shaped lobe.

awn

Fine bristle-like appendage; e.g. terminating or on the back of glumes and/or lemmas of some grass spikelets.

axil

The upper angle between one part of a plant and another; e.g. the stem and a leaf.

axile

On an axis; of a placenta, on the central axis of the ovary.

axillary

Borne in or arising from the axil of a leaf.

axis

A line passing through the centre of something; it usually refers to the main stem of a whole plant or inflorescence.