The document provides a comprehensive overview of wood characteristics, including its definition, types (softwood and hardwood), and anatomical features such as vessels, fibers, and parenchyma. It also discusses the growth processes of trees, including the formation of growth rings, heartwood and sapwood, and the role of tylosis and resin canals. Additionally, it touches on dendrochronology, the study of tree rings for age determination, and various types of heartwood based on pore size transition within growth rings.

1. Characteristics of wood:
Wood:

2. Definition of Wood:
 Secondary xylem
 Wood is a complex biological structure,a
composite of many chemistries and cell types
acting together to serve the need of a living plant.
 It is a three dimensional, anisotropic and
hygroscopic raw material which mainly composed
of cellulose hemicellulose and lignin.

3. Types of Wood:
 Softwood:
 Softwoods are not all soft,lightweight wood
 They are those woods that come from
gymnosperm(mostly conifers)
 They are generaly needle leaved evergreen trees
such as pines(pinus) and spruce(picea)
 Hard Wood:
 Hardwoods are not all have hard, heavy wood
that come from angiosperms(flowering Plants)
 They are typically broad leaf deciduous trees
such as maple(Acer),birch(betula),and Oak
(Quercus).

4. Anatomy of Hard Wood:
 Vessels (pores):
 When viewed from the endgrain vessels simply
appear to be holes in the wood
 What are commonly referred to as pores?
 Parenchyma:
 Parenchyma cells have thin walled storage unit.
In hardwoods parenchyma is long tapered
longitudinal cells, brick shaped epithelium around
gum canals and ray cells.

5. Parenchyma Types:
 Apotracheal Parenchyma
 Paratracheal Parenchyma
 Banded Parenchyma

6. Rays:
 In Hardwood,Rays may be:
 Uniserate: one cell wide
 Biserate: two cells wide
 Multi -serate: may cells wide
 Ray width varies between and within species.

7. Rays:
 Procumbent ray: In radial views,procumbent ray
cells are elongated horizontally.
 Upright ray: upright ray cells are either squarish or
vertically oriented.
 Tylosis:
 Saclike or cystlike structures prtrude in vessels by
parenchyma cell through a pit pair.
 They commonly formed in hard wood as a result of
wounding and effectively act to prevent water lose
from the area around damage tissues
 They may also develop as result of infection from
fungi and bacteria,again to prevent water lose

8. Fibers:
 In a living trees hardwood fiber having strong
thick cell walls that mainly serve to support and
strengthen the trunk.
 When viewed from endgrain,fibers are very small
can’t be seen individually.
 Instead,fibers can only be distinguished in a
broader sense as colored area which form the
backup of wood grain.

9. Parenchyma:
 Much like tracheids, parenchyma are oriented
along the length of the tree trunk and are
sometimes referred to as longitudinal or axial
parenchyma.
 Axial parenchyma cells are similar in size and
shape to ray parenchyma cells, but they are
vertically oriented and stacked one on top of the
other to form a parenchyma strand.

10. Anatomy of Softwood:
 Tracheids are long cells that are often more then
100 times longer(1to 10 mm) than wide and they
are the major components of softwood making up
over 90% of the volume of the wood.
 They serve both the conduction and mechanical
needs of softwood.

11. Rays:
 With the exception of special fusifom rays which occur
in conjuction with resin canals,regular softwood rays
are usually one to two slides wide.
 Because these normal rays are much narrower,and
lack unique characteristics that are observable with a
10x hand lense.
 Resin Canals:
 Resin canals sometimes referred to as resin ducts,are
unique to conifers.
 They are technically not individual cells,but are
actually open,tube like spaces bordered by special
cells that have the ability to secrete pitch or resin into
the neighbouring openings(canal).

12. Resin Canals:
 One of the apparent purposes of these ducts is to
protect and seal up a wound by excuding resin tot
cover the damage area of the tree.
 Accordingly in rare instances, some softwood
species that don’t normally have reason ducts will
develop them as a result of trauma.

13. Content:
 Introduction
 Ontogeny of secondary vascular tissues
 Growth Ring
 Heart wood
 Types of heart wood
 Sap wood
 Wood parenchyma

14.  In most dicotyledons and gymnosperm, the stem
increase in girth by the actively of lateral meristems.
A tree stem consists of three area. Pith,xylem and
bark. The central pith usually bare visible and does
not increase in size through the life of tree.
 A cylinder of wood,known scientifically as xylem rise
in diameter with age and rate of growth.and finaly the
bark sheath can be subdivided into inner bark and
outer bark.
 New wood or inner bark are added each year by the
activity of a layer of deviding cells,sandwiched
between the inner bark and sapwood.New bark
production is relatively small compared with wood
production and bark is continually being shed to the
outside of the stem, thus in older trees the greatest
volume of the stem is wood.since new wood is added
to the outside of existing wood, the oldest wood is
close to the pith,and the most recent is close to the

15. Ontogeny of secondary vascular
tissues:
 The initiation of secondary vascular tissues occur
after the maturation of secondary xylem and
phloem.At the stage of cambium is represented
by single layer of cells.
 The primary tissues lying outside the secondary
vascular tissues are subjected to the pressure
from the inside by the enlarging secondary
vascular cylinder.
 The primary phloem is crushed and become non-
conducting.

16. Growth ring:
 The secondary xylem in the stem of perennial
palnts comonly consists of concentric layers,
each one of which represent a seasonal
increment.
 In transverse section of the axis,these layers
appear as a ring and are called annual rings or
growth rings.
 Each year represents the growth of one year,the
width of the growth rings varies greatly and
depends upon the rate of growth of tree.

17.  In regions with pronounced cold season, the activity
of cambium takes place only during the spring and
summer seasons thus giving rise to the growth in
diameter of woody plants.
 In spring or summer the cambium is more active and
form greater number of vessels with water cavities,in
winter or autumn season.However there is less need
of for sap transport, the cambium is less active.
 Early wood:
 The wood developed in the summer or spring season
is called spring wood or early wood.
 Early wood is inner layer of growth rings.The early
wood zones of a growth rings typically consists of
thin walled,larger diameter cells and also appear
lighter in color.

18.  Late wood:
 The wood form in the winter or autumn season is
known as autumn wood or late wood.late wood is a
outer layer of growth ring.
 Late wood zones thicked walled,smaller diameter
cells and also appear darker or brown shade in color.

19. Dendrochronology:
 Each annual ring corresponds to one year’s
growth and on the basis of these rings the age of
particular plant can easily be calculated.The
determination of age of a tree by counting the
annual ring is known as dendrochronology.
 Sometimes two annual rings are formed in single
year and such cases the counting of annual ring
does not show the correct age of the tree.
 This happens perhaps because of the drought
condition prevalled in the middle of a growth.

20. Tylosis:
 In many plants the walls of xylem vessels
produce ballon like out growth into the lumen of
the vessels are called Tylosis.Usually these
structure are formed in secondary xylem.Tylosis
are formed by the enlargement of pit membranes
of the half bordered pit present in between a
parenchyma cell and a vessels or a tracheids.

21. Heart Wood and Sap Wood:
 Sap wood:
 The outer region of old tree is sap wood or
alburnum
 The sap wood consists of recently fromed xylem
elements
 It is not hard and durable.
 This is of light color and contain some living cells
also in association of vessels and fibres.
 Generally the vessels are not plugged with
tylosis.

22. Heart wood:
 Heart Wood:
 The cantral region of the old tree is called heart
wood or duramin
 It is filled up tannins resin gums and other
substances
 It is hard and durable.
 It looks black or dark brown due to the presence
of varies substances in it.
 Usually the vessels remain plugged with Tylosis.

23. Types of Heart Wood:
 Ring porous hardwoods:
 For some group of species(oaks) the early wood/late
wood transition occurs abruptly and is very distinct.
 Within each growth ring a band of large early
woodvessels is clearly visible to the naked eye,after
which a band of late wood vessels appears much
smaller and requires the use of hand lens to see.
 Semi-ring porous hardwood:
 For another type of species(black walnut,butternut)
pore transition from large to small diameter within a
growth ring is gradual. The pores in the early wood
zone have a large diameter that gradually decrease in
size as pores enter the late wood zone.

24. Cont…
 Diffuse porous hard wood:
 The last group species have vessels(pores)that are uniform in
size across the entire growth ring(yellow poplar,gum and
maple).These vessels are usually small,uniform in size and
are very difficult to see with the naked eye.
 Sap wood:
 Resin Canals:
 The first step after making the determination that a wood
specimen is soft due to the absence of pores is to inspect the
cross section surface for the presence of resin canals.resin
canals are tubular passage in wood that excude pitch,or resin
to seal off wounds that occur due to insect or mechanical
damage.resin canal most offten occur in or near the late wood
zone of the growth rings.softwoods can be separated into two
classifications based on the presence or absence of resin
canals.