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 (ferns, gymnosperms and angiosperms), particularly flowering plants (angiosperms). Non-vascular plants (bryophytes), with their different evolutionary background, tend to have separate terminology. Although plant morphology (the external form) is integrated with plant anatomy (the internal form), 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 (plant) – any flat surfaced structure emerging from the side or summit of an organ; seeds, stems.
Plant habit
Plant habit or habitus 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 (lianas)—will gradually acquire woody (lignaceous) 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 (lignification) is commonest in the spermatophytes (seed bearing plants) 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.
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 (i.e. close distances between nodes on the plant stem. See also radical, where leaves arise apparently without stems. Acid plant – plants with acid saps, normally due to the production of ammonium salts (malic and oxalic acid) 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 (to describe leaves or bracts). 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 (see also Indeterminate). 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 (ones that form on the leaves). 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 (see also Determinate). 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 (cf. rostellum). 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. – Being woody at the base, with herbaceous branches. 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.
Plant structures
Introduction
Plant structures or organs fulfill specific functions, and those functions determine the structures that perform them. Among terrestrial (land) plants, the vascular and non-vascular plants (Bryophytes) evolved independently in terms of their adaptation to terrestrial life and are treated separately here (see Bryophytes).
Life cycle Common structural elements are present in the embryonic part of the life cycle, which is the diploid multicellular phase. The embryo develops into the sporophyte, which at maturity produces haploid spores, which germinate to produce the gametophyte, the haploid multicellular phase. The haploid gametophyte then produces gametes, which may fuse to form a diploid zygote, and finally an embryo. This phenomenon of alternating diploid and haploid multicellular phases is common to the embryophytes (land plants) and is referred to as the alternation of generations. A major difference between vascular and non-vascular plants is that in the latter the haploid gametophyte is the more visible and longer-lived stage. In vascular plants, the diploid sporophyte has evolved as the dominant and visible phase of the life cycle. In seed plants and some other groups of vascular plants the gametophyte phases are strongly reduced in size and contained within the pollen and ovules. The female gametophyte is entirely contained within the sporophyte's tissues, while the male gametophyte in its pollen grain is released and transferred by wind or animal vectors to fertilize the ovules.
Morphology