Glossary of plant morphology

Non-vascular plants (bryophytes), with their different evolutionary background, tend to have separate terminology.

While many plants fit neatly into some main categories, such as grasses, vines, shrubs, or trees, others can be more difficult to categorise.

The process of wood formation (lignification) is commonest in the spermatophytes (seed bearing plants) and has evolved independently a number of times.

[6] Common structural elements are present in the embryonic part of the life cycle, which is the diploid multicellular phase.

The haploid gametophyte then produces gametes, which may fuse to form a diploid zygote, and finally an embryo.

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.

[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).

In angiosperms, if the female sporangium is fertilised, it becomes the fruit, a mechanism for dispersing the seeds produced from the embryo.

New growth occurs at the tips (apices) of both the shoot and roots, where the undifferentiated cells of the meristem divide.

The stem also serves as a conduit, from roots to overhead structures, for water and other growth-enhancing substances.

The leaves, which emerge from the shoot, are specialised structures that carry out photosynthesis, and gas (oxygen and carbon dioxide) and water exchange.

The leaves also possess vascular bundles, which are generally visible as veins, whose patterns are called venation.

A secondary smaller bract is a bracteole (bractlet, prophyll, prophyllum), often on the side of the pedicel, and generally paired.

[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.

These leaf primordia become specialised as sporophylls, leaves that form areas called sporangia, which produce spores, and cavitate internally.

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.

A carpel is a modified megasporophyll consisting of two or more ovules, which develop conduplicatively (folded along the line).

Within the carpel the megasporangium form the ovules, with its protective layers (integument) in the megaspore, and the female gametophyte.

[8] Most flowers have both male and female organs, and hence are considered bisexual (perfect), which is thought to be the ancestral state.

Finally, trioecious plants have bisexual, staminate, or carpellate flowers on different individuals.

This generally requires an external agent such as wind or insects to carry the pollen from the stamen to the vicinity of the ovule.

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.

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