Glossary of plant morphology


This page provides a glossary of plant morphology. Botanists and other biologists who study plant morphology use a number of different terms to classify and identify plant organs and parts that can be observed using no more than a handheld magnifying lens. This page provides help in understanding the numerous other pages describing plants by their various taxa. The accompanying page—Plant morphology—provides an overview of the science of the external form of plants. There is also an alphabetical list: Glossary of botanical terms. In contrast, this page deals with botanical terms in a systematic manner, with some illustrations, and organized by plant anatomy and function in plant physiology.
This glossary primarily includes terms that deal with vascular plants, particularly flowering plants. Non-vascular plants, with their different evolutionary background, tend to have separate terminology. Although plant morphology is integrated with plant anatomy, the former became the basis of the taxonomic description of plants that exists today, due to the few tools required to observe.
Many of these terms date back to the earliest herbalists and botanists, including Theophrastus. Thus, they usually have Greek or Latin roots. These terms have been modified and added to over the years, and different authorities may not always use them the same way.
This page has two parts: The first deals with general plant terms, and the second with specific plant structures or parts.

General plant terms

  • Abaxial – located on the side facing away from the axis.
  • Adaxial – located on the side facing towards the axis.
  • Dehiscent – opening at maturity
  • Gall – outgrowth on the surface caused by invasion by other lifeforms, such as parasites
  • Indehiscent – not opening at maturity
  • Reticulate – web-like or network-like
  • Striated – marked by a series of lines, grooves, or ridges
  • Tesselate – marked by a pattern of polygons, usually rectangles
  • Wing – any flat surfaced structure emerging from the side or summit of an organ; seeds, stems.

    Plant habit

refers to the overall shape of a plant, and it describes a number of components such as stem length and development, branching pattern, and texture. While many plants fit neatly into some main categories, such as grasses, vines, shrubs, or trees, others can be more difficult to categorise. The habit of a plant provides important information about its ecology: that is, how it has adapted to its environment. Each habit indicates a different adaptive strategy. Habit is also associated with the development of the plant. As such, it may change as the plant grows and is more properly called its growth habit. In addition to shape, habit indicates plant structure; for instance, whether the plant is herbaceous or woody.
Each plant commences its growth as a herbaceous plant. Plants that remain herbaceous are shorter and seasonal, dying back at the end of their growth season. Woody plants—such as trees, shrubs and woody vines —will gradually acquire woody tissues, which provide strength and protection for the vascular system, and they tend to be tall and relatively long lived. The formation of woody tissue is an example of secondary growth, a change in existing tissues, in contrast to primary growth that creates new tissues, such as the elongating tip of a plant shoot. The process of wood formation is commonest in the spermatophytes and has evolved independently a number of times. The roots may also lignify, aiding in the role of supporting and anchoring tall plants, and may be part of a descriptor of the plant's habit.
Plant habit can also refer to whether the plant possesses any specialised systems for the storage of carbohydrates or water, allowing the plant to renew its growth after an unfavourable period. Where the amount of water stored is relatively high, the plant is referred to as a succulent. Such specialised plant parts may arise from the stems or roots. Examples include plants growing in unfavourable climates, very dry climates where storage is intermittent depending on climatic conditions, and those adapted to surviving fires and regrowing from the soil afterwards.
Some types of plant habit include:
  • Herbaceous plants : a plant whose structures above the surface of the soil, vegetative or reproductive, die back at the end of the annual growing season, and never become woody. While these structures are annual in nature, the plant itself may be annual, biannual, or perennial. Herbaceous plants that survive for more than one season possess underground storage organs, and thus are referred to as geophytes.
Terms used in describing plant habit, include:
  • Acaulescent – the leaves and inflorescence rise from the ground, and appear to have no stem. They are also known as rosette forms, some of the many conditions that result from very short internodes
  • Actinomorphic – parts of plants that are radially symmetrical in arrangement.
  • Arborescent – growing into a tree-like habit, normally with a single woody stem.
  • Ascending – growing uprightly, in an upward direction.
  • Assurgent – growth ascending.
  • Branching – dividing into multiple smaller segments.
  • Caducous – falling away early.
  • Caulescent – with a well-developed stem above ground.
  • Caulirosulate - arranged in rose-like clusters at the end of the stem.
  • Cespitose – forming dense tufts, normally applied to small plants typically growing into mats, tufts, or clumps.
  • Creeping – growing along the ground and producing roots at intervals along the surface.
  • Deciduous – falling away after its function is completed.
  • Decumbent – growth starts off prostrate and the ends turn upright.
  • Deflexed – bending downward.
  • Determinate growth – Growing for a limited time, floral formation and leaves.
  • Dimorphic – of two different forms.
  • Ecad – a plant assumed to be adapted to a specific habitat.
  • Ecotone – the boundary that separates two plant communities, generally of major rank – trees in woods and grasses in savanna for example.
  • Ectogenesis – variation in plants due to conditions outside of the plants.
  • Ectoparasite – a parasitic plant that has most of its mass outside of the host, the body and reproductive organs of the plant live outside of the host.
  • Epigeal – living on the surface of the ground. See also terms for seeds.
  • * Epigean – occurring on the ground.
  • * Epigeic – plants with stolons on the ground.
  • * Epigeous – on the ground. Used for leaf fungus that live on the surface of the leaf.
  • Epiphloedal – growing on the bark of trees.
  • * Epiphloedic – an organism that grows on the bark of trees.
  • Epiphyllous – growing on the leaves. For example, Helwingia japonica has epiphyllous flowers.
  • Epiphyte – growing on another organism but not parasitic. Not growing on the ground.
  • * Epiphytic – having the nature of an epiphyte.
  • Equinoctial – a plant that has flowers that open and close at definite times during the day.
  • Erect – having an essentially upright vertical habit or position.
  • Escape – a plant originally under cultivation that has become wild, a garden plant growing in natural areas.
  • Evergreen – remaining green in the winter or during the normal dormancy period for other plants.
  • Eupotamous – living in rivers and streams.
  • Euryhaline – normally living in salt water but tolerant of variable salinity.
  • Eurythermous – tolerant of a wide range of temperatures.
  • Exclusive species – confined to specific location.
  • Exotic – not native to the area or region.
  • Exsiccatus – a dried plant, most often used for specimens in a herbarium.
  • Indeterminate growth – Inflorescence and leaves growing for an indeterminate time, until stopped by other factors such as frost.
  • Lax – non upright, growth not strictly upright or hangs down from the point of origin.
  • Lithophyte – Growing on rocks
  • * Endolithic – growing in crevices of rocks.
  • * Epilithic – growing on the surface of rocks.
  • Mallee – a term applied to certain Australian species which grow with multiple stems springing from an underground lignotuber.
  • Parasitic – using another plant as a source of nourishment.
  • Precocious – flowering before the leaves emerge.
  • Procumbent – growing prostrate or trailing, but not rooting at the nodes.
  • Prostrate – lying flat on the ground, leaves, stems or even flowers in some species.
  • Repent – creeping.
  • Rosette – cluster of leaves with very short internodes that are crowded together, normally on the surface of the soil but sometimes higher on the stem.
  • * – like a rosette.
  • * Rosulate – arranged into a rosette.
  • Runner – an elongated, slender branch that roots at the nodes or tip.
  • Stolon – A branch that forms near the base of the plant, grows horizontally, and roots and produces new plants at the nodes or apex.
  • * Stoloniferous – plants producing stolons.
  • Semi-erect – Not growing perfectly straight.
  • Suffrutescent – somewhat shrubby, or shrubby at the base.
  • Upright – Growing upward.
  • Virgate – wand-like, slender erect growing stem with many leaves or very short branches.
  • Woody – forming secondary growth laterally around the plant so as to form wood.

    Duration

Duration of individual plant lives are described using these terms:
  • Acme – the time when the plant or population has its maximum vigor.
  • Annual – plants that live, reproduce, and die in one growing season.
  • Biennial – plants that need two growing seasons to complete their life cycle, normally completing vegetative growth the first year and flowering the second year.
  • Herbs – see herbaceous.
  • Herbaceous – plants with shoot systems that die back to the ground each year – both annual and non-woody perennial plants.
  • Herbaceous perennial – non-woody plants that live for more than two years, with the shoot system dying back to soil level each year.
  • Woody perennial – true shrubs and trees, and some vines, with shoot systems that remain alive above the soil level from one year to the next.
  • Monocarpic – plants that live for a number of years then, after flowering and seed setting, die.