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In
botany Botany, also called , plant biology or phytology, is the science of plant life and a branch of biology. A botanist, plant scientist or phytologist is a scientist who specialises in this field. The term "botany" comes from the Ancient Greek wo ...

botany
, the trunk (or bole) is the
stem Stem or STEM may refer to: Biology * Plant stem, the aboveground structures that have vascular tissue and that support leaves and flowers ** Stipe (botany), a stalk that supports some other structure ** Stipe (mycology), the stem supporting the c ...

stem
and main
wood Wood is a porous and fibrous structural tissue found in the stems and roots of tree In botany, a tree is a perennial plant with an elongated Plant stem, stem, or trunk (botany), trunk, supporting branches and leaves in most species. ...

wood
en axis of a
tree In botany, a tree is a perennial plant with an elongated Plant stem, stem, or trunk (botany), trunk, supporting branches and leaves in most species. In some usages, the definition of a tree may be narrower, including only wood plants with se ...

tree
, which is an important feature in tree identification, and which often differs markedly from the bottom of the trunk to the top, depending on the species. The trunk is the most important part of the tree for
timber Lumber, also known as timber, is wood Wood is a porous and fibrous structural tissue found in the stems and roots of tree In botany, a tree is a perennial plant with an elongated Plant stem, stem, or trunk (botany), trunk, sup ...

timber
production. Trunks occur both in "true" woody plants as well as non-woody plants such as palms and other
monocots Monocotyledons (), commonly referred to as monocots, (Lilianae ''sensu'' Chase & Reveal) are grass and grass-like flowering plants (angiosperms), the seeds of which typically contain only one Embryo#Plant embryos, embryonic leaf, or cotyledon. The ...
, though the internal physiology is different in each case. In all plants, trunks thicken over time due to the formation of
secondary growth In botany Botany, also called , plant biology or phytology, is the science of plant life and a branch of biology. A botanist, plant scientist or phytologist is a scientist who specialises in this field. The term "botany" comes from the Anc ...
(or in monocots, pseudo-secondary growth). Trunks can be vulnerable to damage, including
sunburn Sunburn is a form of radiation burn A radiation burn is a damage to the skin Skin is the layer of usually soft, flexible outer tissue covering the body of a vertebrate animal, with three main functions: protection, regulation, and sensation. ...

sunburn
. Trunks which are cut down during logging are generally called logs and if they are cut to a specific length bolts. The term "log" is informally used in
English English usually refers to: * English language English is a West Germanic languages, West Germanic language first spoken in History of Anglo-Saxon England, early medieval England, which has eventually become the World language, leading lan ...

English
to describe any felled trunk not rooted in the ground. A
stump
stump
is the part of a trunk remaining in the ground after the tree has been felled.


Structure of the trunk

The trunk consists of five main parts: the bark, inner bark, cambium, sapwood, and heartwood. From the outside of the tree working in, the first layer is the bark; this is the protective outermost layer of the trunk. Under this is the inner bark which is made of the
phloem Phloem (, ) is the living tissue Tissue may refer to: Biology * Tissue (biology), an ensemble of similar cells that together carry out a specific function * ''Triphosa haesitata'', a species of geometer moth found in North America * ''Triphosa ...

phloem
. The phloem is how the tree transports nutrients from the roots to the shoots and vice versa. The next layer is the
cambium A cambium (plural cambia or cambiums), in plants, is a tissue layer that provides partially undifferentiated cell Cell most often refers to: * Cell (biology), the functional basic unit of life Cell may also refer to: Closed spaces * Monastic ...
, a very thin layer of undifferentiated cells that divide to replenish the phloem cells on the outside and the xylem cells to the inside. The cambium contains the growth
meristem The meristem is a type of tissue Tissue may refer to: Biology * Tissue (biology), an ensemble of similar cells that together carry out a specific function * ''Triphosa haesitata'', a species of geometer moth found in North America * ''Triphosa du ...
of the trunk. Directly to the inside of this is the sapwood, or the living
xylem Xylem is one of the two types of transport tissue Tissue may refer to: Biology * Tissue (biology), an ensemble of similar cells that together carry out a specific function * ''Triphosa haesitata'', a species of geometer moth found in North Ame ...

xylem
cells. These cells transport the water through the tree. The xylem also stores starch inside the tree. Finally at the center of the tree is the heartwood. The heartwood is made up of old xylem cells that have been filled with resins and minerals that keep other organisms from growing and infecting the center of the tree. File:Timber floating.jpg, Raft of timber logs File:Corylus avellana12.jpg, Cross section of a
hazel The hazel (''Corylus'') is a genus Genus /ˈdʒiː.nəs/ (plural genera /ˈdʒen.ər.ə/) is a taxonomic rank In biological classification In biology, taxonomy () is the scientific study of naming, defining (Circumscription (taxon ...

hazel
bole File:A Lovely Rotting Log - geograph.org.uk - 998345.jpg, Log being decomposed by
bracket fungi Polypores are a group of Fungus, fungi that form large fruiting bodies with pores or tubes on the underside (see Polypore#Delimitation (morphology), Delimitation for exceptions). They are a morphological group of Basidiomycota, basidiomycetes-lik ...

bracket fungi
File:Olivenhain Alexandroupolis.jpg, Trunk of an
Olive tree The olive, known by the botanical name ''Olea europaea'', meaning "European olive", is a species In biology, a species is the basic unit of biological classification, classification and a taxonomic rank of an organism, as well as a unit o ...

Olive tree
File:דקל תמר מצוי חתך גזע דמוי עץ (3).jpg,
Palmae The Arecaceae is a of in the . Their growth form can be s, shrubs, -like and stemless plants, all commonly known as palms. Those having a tree-like form are called palm trees. Currently 181 with around 2,600 are known, most of them rest ...
Phoenix dactylifera ''Phoenix dactylifera'', commonly known as date or date palm, is a flowering plant species in the palm family, Arecaceae, cultivated for its edible sweet fruit. The species is widely cultivated across Northern Africa, the Middle East and South ...

Phoenix dactylifera
Trunk section.


See also

*
Bark Bark may refer to: * Bark (botany), an outer layer of a woody plant * Bark (sound), a vocalization of some animals Places * Bark, Germany * Bark, Warmian-Masurian Voivodeship, Poland Arts, entertainment, and media * ''Bark'' (Jefferson Airp ...
*
Basal area Basal area is the cross-sectional area of trees In botany Botany, also called , plant biology or phytology, is the science Science (from the Latin word ''scientia'', meaning "knowledge") is a systematic enterprise that Scientif ...
*
Diameter at breast height Diameter at breast height, or DBH, is a standard method of expressing the of the or of a standing . DBH is one of the most common measurements. Tree trunks are measured at the height of an adult's breast, which is defined differently in dif ...

Diameter at breast height
*
Log (disambiguation) Log usually refers to: * Trunk (botany) In botany, the trunk (or bole) is the plant stem, stem and main wooden axis of a tree, which is an important feature in tree identification, and which often differs markedly from the bottom of the trunk to ...
*
Tree measurement Trees have a wide variety of sizes and shapes and growth habits. Specimens may grow as individual trunks, multitrunk masses, coppices, clonal colonies, or even more exotic tree complexes. Most champion tree programs focus finding and measuring the ...
*
Tree volume measurementTree volume is one of many Tree measurement, parameters that are measured to document the size of individual trees. Tree volume measurements serve a variety of purposes, some economic, some scientific, and some for sporting competitions. Measurements ...


References


External links


Inside a tree trunk
from the
University of the Western Cape The University of the Western Cape (UWC) is a public university located in Bellville, a suburb of the City of Cape Town The City of Cape Town ( af, Stad Kaapstad; xh, IsiXeko saseKapa) is the metropolitan municipality which governs the ...
Plant morphology ''Plant morphology'' is the field in botany that studies the diversity in forms, with the naked eye or slight optical magnification. This is opposed to plant anatomy (see :Plant anatomy) that needs to cut into plants to be able to study its subject, ...
de:Baum#Aufbau des Baumstammes {{tree-stub