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 describe plant organs and parts that can be observed with the human eye using no more than a hand held magnifying lens. These terms are used to identify and classify plants. This page is provided to 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 studying the external form of plants. There is also an alphabetical list, a Glossary of botanical terms, while this page deals with botanical terms in a systematic manner, with some illustrations. The internal structure is dealt with in Plant anatomy, and function in Plant physiology.[1]

Primarily, these are terms that deal with the vascular plants (ferns, gymnosperms and angiosperms), particularly the flowering plants (Angiosperms). In contrast the non-vascular plants (Bryophytes), with their different evolutionary background, tend to have their own particular terminology. Although plant morphology (the external form) is integrated with plant anatomy (the internal form), the former which requires few tools was the basis of the taxonomic description of plants that exists today.[2][3]

Since the terms used have been handed down from the earliest herbalists and botanists, as far back as Theophrastus, they are usually Greek or Latin in form. These terms have been modified and added to over the years and different authorities may not always use them in exactly the same way.[2][3] This page has two parts. The first deals with general plant terms, and the second with specific plant structures or parts.

General plant terms

Plant habit

Plant habit refers to the overall shape of a plant. It has a number of components such as stem length and development, branching pattern, and texture. While many plants fit easily 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 ecological strategy. Habit is also associated with the development of the plant and may change as the plant grows, more properly called its growth habit. In addition to shape, habit indicates its structure, for instance whether herbaceous or woody. Each plant commences its growth as a herbaceous plant, while 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.[4] While woody plants tend to be tall and relatively long lived, herbaceous plants are shorter and seasonal, dying back at the end of their growth season. 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.

Another plant habit refers to whether the plant possesses any specialised systems for the storage of carbohydrates or water, allowing it to renew 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 that can regrow from the soil afterwards.

Some types of plant habit include:

Terms used in describing plant habit, include:


Duration of individual plant lives are described using these terms:

Plant structures


Life cycles
Alternating generations: Haploid gametophyte (top), diploid sporophyte (bottom)
Angiosperms. Only the sporophyte is visible, the gametophytes being the pollen and ovule

Plant structures or organs fulfil 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).[6]

Life cycle

Their common elements occur in the embryonic part of the life cycle, which is their diploid multicellular phase. The embryo develops into the sporophyte, which in turn produces spores, the haploid multicellular phase, from which arises the gametophyte stage. 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 phases common to embryophytes (land plants) is referred to as the alternation of generations. One of the major differences between non vascular and vascular plants is that in the former it is the haploid gametophyte that is the more visible and longer lived stage. In the vascular plants evolution has created the diploid sporophyte as the dominant and visible phase of the life cycle. The gametophyte phase is reduced to the pollen and ovules and is entirely contained within the sporophyte.[1]


Amongst the vascular plants the structures and functions of the Pteridophyta (ferns) which reproduce seedlessly are also sufficiently different to justify separate treatment, as here (see Pteridophytes). The remainder of the vascular plant sections address the higher plants (Spermatophytes or Seed Plants, i.e. Gymnosperms and Angiosperms or flowering plants). In the higher plants the terrestrial sporophyte has evolved specialised parts. In essence they have an underground component and an upper aerial component. The lower underground part develops roots that seek water and nourishment from the soil, while the upper component or shoot moves towards the light and develops a plant stem, leaves and specialised reproductive structures (sporangia). In angiosperms, the sporangia are located in the stamen anthers (microsporangia) and ovules (megasporangia). The specialised sporangia bearing stem is the flower. In angiosperms, if the female sporangium is fertilised, it becomes the fruit, a mechanism for dispersing the seeds produced from the embryo. [6]

Vegetative structures

Thus the terrestrial sporophyte has two growth centres, the stem growing upwards while the roots grow downwards. New growth occurs at the tips (apices) of the shoot and roots where the undifferentiated cells of the meristem divide. Branching occurs to form new apical meristems. Growth of the stem is indeterminate in pattern (not pre-determined to stop at a particular point).[1] The functions of the stem are to raise and support the leaves and reproductive organs above the level of the soil to facilitate absorption of light for photosynthesis, gas exchange, water exchange (transpiration) pollination and seed dispersal. It also serves as a conduit for water and other growth substances between the roots and overhead structures. This occurs in specialised tissues known as vascular bundles, which give the name 'vascular plants' to the angiosperms. The point of insertion on the stem of leaves or buds is a node, and the space between two successive node, an internode.

Also emerging from the shoot are the leaves, specialised structures that carry out photosynthesis, and gas (oxygen and carbon dioxide) and water exchange. They are lined by an outer layer or epidermis, coated with a waxy waterproof protective layer, but punctuated by specialised pores, known as stomata, which regulate gas and water exchange. The leaves also possess vascular bundles, which are generally visible as veins, and their pattern is called venation. Leaves tend to have a shorter life span than the stems or branches that bear them, and when they fall, an area at the attachment zone, called an abscission zone leaves a scar on the stem.

In the angle (adaxial) between the leaf and the stem, is the axil. Here can be found buds (axillary buds), which are miniature and often dormant branches with their own apical meristem. They are often covered by leaves.

Floral structure
Floral structure
Location of main floral parts in angiosperms
1: Pedicel 2: Receptacle 3: Nectary 4: Sepal 5: Petal 6: Filament 7: Anther 8: Stigma 9: Style 10: Ovary 11: Ovule 12: Bract

The flower, which is one of the defining features of angiosperms, is essentially a stem, whose leaf primordia become specialised, following which the apical meristem stops growing, a determinate growth pattern, in contrast to vegetative stems.[1][6] The flower stem is known as a pedicel, and those flowers with a stalk are called pedicellate, while those without are called sessile.[7] In the angiosperms, the flowers are arranged on a flower stem as an inflorescence, though these structures are very different in gymnosperms and angiosperms, which are dealt with in more detail here. Just beneath (subtended) the flower there may be a modified and usually reduced leaf, called a bract. A secondary smaller bract is a bracteole (bractlet, prophyll, prophyllum), often on the side of the pedicel, and generally paired. A series of bracts subtending the calyx (see below) is an epicalyx.[7]

In angiosperms, the specialised leaves that play a part in reproduction are arranged around the stem in an ordered fashion, from the base to the apex of the flower. The floral parts are arranged at the end of a stem without any internodes, the receptacle (also called the floral axis, or thalamus) which is generally very small. Some flower parts are solitary, while others may form a tight spiral or whorl, around the flower stem. First, at the base, are those non-reproductive structures involved in protecting the flower when it is still a bud, the sepals, then those parts that play a role in attracting pollinators and are typically coloured, the petals, which together with the sepals make up the perianth (perigon, perigonium). If the perianth is not differentiated into sepals and petals, they are collectively known as tepals. If the perianth is differentiated, the outer whorl of sepals forms the calyx, and the inner whorl of petals, the corolla. In some flowers, a tube or cup like hypanthium (floral tube) is formed above or around the ovary and bears the sepals, petals and stamens. There may also be a nectary producing nectar. Nectaries may develop on or in the perianth, receptacle, androecium (stamens), or gynoecium. In some flowers nectar may be produced on nectariferous disks. Disks may arise from the receptable and are doughnut or disk shaped. They may also surround the stamens (extrastaminal), be at their bases (staminal) or be inside the stamina (intrastaminal).[8]

Reproductive structures

Finally, the actual reproductive parts form the innermost layers of the flower. These leaf primordia become specialised as sporophylls, leaves that form areas called sporangia, which produce spores, and cavitate internally. The sporangia on the sporophytes of pteridophytes are visible, but those of gymnosperms and angiosperms are not. In the angiosperms there are two types. Some form male organs (stamens), the male (microsporangia), producing microspores. Others form female organs (carpels), the female (megasporangia) which produce a single large megaspore.[8] These in turn produce the male gametophytes and female gametophytes

These two components are the androecium and gynoecium respectively. The Androecium (literally, men's house) is a collective term for the male organs (stamens or microsporophylls). While sometimes leaflike (laminar), more commonly they consist of a long thread-like column, the filament, surmounted by a pollen bearing anther. The anther usually consists of two fused thecae. A theca is two microspoorangia. The gynoecium (women's house) is the collective term for the female organs (carpels). A carpel is a modified megasporophyll consisting of two or more ovules, which develops conduplicatively (folded along the line). The carpels may be single of collected together to form an ovary, and contain the ovules. Another term, pistil, refers to the ovary as its expanded base, the style, a column arising from the ovary, and an expanded tip, the stigma.[8]

Within the stamen the microsporangium forms grains of pollen, surrounded by the protective microspore, which forms the male gametophyte. Within the carpel the megasporangium form the ovules, with its protective layers (integument) in the megaspore, and the female gametophyte. Unlike the male gametophyte, which is transported in the pollen, the female gametophyte remains within the ovule.[8]

Most flowers have both male and female organs, and hence are considered bisexual (perfect), which is thought to be the ancestral state. However others have either one or the other and are therefore unisexual or imperfect. In which case they may be either male (staminate) or female (pistillate). Plants may bear either all bisexual flowers (hermaphroditic), both male and female flowers (monoecious) or only one sex (dioecious), in which case separate plants are either male or female flower bearing. Where both bisexual and unisexual flowers exist on the same plant, it is called polygamous. Polygamous plants may have bisexual and staminate flowers (andromonoecious) or bisexual and pistillate flowers (gynomonoecious), or both (trimonoecious). Other combinations include the presence of bisexual flowers on some individual plants and staminate on others (androdioecious) or bisexual and pistillate (gynodioecious). Finally trioecious plants have bisexual, staminate or pistillate flowers on different individuals. Arrangements other than hermaphroditic help to ensure outcrossing.[9]

Fertilisation and embryogenesis

The development of the embryo and gametophytes is called embryology. The study of pollens which persist in soil for many years is called palynology. Reproduction occurs when male and female gametophytes interact. This generally requires an external agent such as wind or insects to carry the pollen from the stamen to the vicinity of the ovule. This process is called pollination. In gymnosperms (literally naked seed) pollen comes into direct contact with the exposed ovule. In angiosperms the ovule is enclosed in the carpel, requiring a specialised structure, the stigma, to receive the pollen. On the surface of the stigma, the pollen germinates, that is the male gametophyte penetrates the pollen wall into the stigma, and a pollen tube, an extension of the pollen grain extends towards the carpel carrying with it the sperm cells (male gametes) till they encounter the ovule, where they gain access through a pore in the integument (micropyle) allowing fertilisation to occur. Once the ovule has been fertilised, a new sporophyte develops, protected and nurtured by the female gametophyte, and becomes an embryo. When development stops, the embryo becomes dormant as a seed. Within the embryo are the primordial shoot and root.

In angiosperms, as the seed develops after fertilisation, so does the surrounding carpel, it walls thickening or hardening, developing colours or nutrients that attract animals or birds, often with many layers. This new entity with its dormant seeds is the fruit, whose functions are protecting the seed and dispersing it. In some cases androecium and gynaecium may be fused. The resulting structure is a gynandrium (gynostegium, gynostemium or column) and is supported by an androgynosphore.[8]

Vegetative morphology


Roots generally do not offer many characters used in plant identification and classification, but are important in determining plant duration. In some groups, however, including the grasses, they are very important for proper identification .


Parts of plant stem



Leaf morphology:
Shape, margin and venation.

Leaf Parts: – A complete leaf is composed of a blade, petiole and stipules and in many plants one or more might be lacking or highly modified.

Duration of leaves:


Leaf Arrangement or Phyllotaxy:

Leaf Type:

Leaf Blade Shape:

Main article: Leaf shape

Leaf Base Shape:

Leaf Blade Apex:

Leaf Blade Margins:

Leaf Modifications:

Epidermis and periderm texture

Floral morphology

Basic flower parts

Main article: Gynoecium
Style position
Terminal (apical)


Pedicellate atachment
Sessile attachment
Verticillaster, Lamium album

Insertion of floral parts

Specialized terms

Union of flower parts

Flower sexuality and presence of floral parts

Flower symmetry

Pollination and fertilization

Embryo development

Fruits and seeds

Fruits are the matured ovary of seed bearing plants and they include the contents of the ovary, which can be floral parts like the receptacle, involucre, calyx and others that are fused to it. Fruits are often used to identify plant taxa and help to place the species in the correct family or differentiate different groups within the same family.

Terms for fruits

Fruit types

Scheme of a drupe
Scheme of a pome

Fruits are divided into different types depending on how they form, were or how they open and what parts they are composed of.

Seedless reproduction



  • Amphithecium – The external cell layers of the developing sporangium of a bryophyte. (Note: this term is also used in the mycology of lichens.)
  • Anisosporous – Anisospore production is a rare condition in dioecious bryophytes; meiosis produces two small spores that develop into male gametophytes and two larger spores that develop into female gametophytes; contrast Isosporous.
  • Annulus – in mosses, cells with thick walls along the rim of the sporangium and were the peristome teeth are attached.
  • Apophysis –
  • Archesporium –
  • Arthrodontous –
  • Articulate –
  • Astomous –
  • Basal membrane –
  • Calyptra
  • Capsule –
  • Cleistocarpous –
  • Columella
  • Dehisce –
  • Diplolepidous –
  • Divisural line –
  • Elater – structures derived from the sporangium of liverworts that aid in spore dispersal
  • Endostome –
  • Endothecium –
  • Epiphragm –
  • Exostome –
  • Exothecium –
  • Foot –
  • Gymnostomous –
  • Haplolepidous –
  • Haustorium –
  • Hypophysis –
  • Immersed –
  • Indehiscent –
  • Inoperculate –
  • Isosporous – unlike anisosporous species, whether monoecious or dioecious, all spores are the same size.
  • Nematodontous –
  • Nurse cells –
  • Operculate –
  • Operculum –
  • Oral –
  • Peristome –
  • Pseudoelater – structures derived from the sporangium of hornworts that aid in spore dispersal
  • Seta –
  • Stegocarpous –
  • Stoma –
  • Suboral –
  • Tapetum –
  • Trabecula –
  • Valve –

See also





Anatomy and morphology



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