External Form of a Woody Twig

A woody twig, or stem, is an axis with leaves attached the leaves are arranged in various ways around and on the axis.

-       NODES - The area, or region of a stem where a leaf or leaves are attached or begin to grow and stem region between nodes is called an internode

-       PETIOLE - A structure of a plant that connects the stem of the plant to the blade of the leaf

Axil and Axillary Bud

-       AXIL - The angle between the upper side of a leaf or stem and the stem or branch that supports it

-       AXILLARY BUD - A structure that forms an armpit

-       Scar Tissue on Twigs - Where a leaf falls from the twig, a leaf scar is left behind

-       Stipules - are paired, often somewhat leaflike, appendages that may remain throughout the life of the leaf.

Origin and Development of Stems

-       There is an apical meristem at the tip of each stem, and it is this meristem that contributes to increase in the length of the stem

-       It is protected by bud scales of the bud in which it is located and to a certain extent by leaf primordia

Protoderm - a thin outer layer of the meristem in embryos and growing points of roots and stems, which gives rise to the epidermis.

Procambium – appears to the interior of the protoderm.

Ground meristem - produces two tissues composed by parenchyma cell. Parenchyma tissue in the center of the stem is the pith.

Pith – pith cell is very large and break down shortly after they formed.

Cortex – may become more extensive than the pith, but eventually crushed and replace by new tissue produced stems, which gives rise to the epidermis.

The vascular cambium is often referred to simply as the cambium. The cells of the cambium continue to divide indefinitely, with the divisions taking place mostly in a plane parallel to the surface of the plant.

Lenticels - develop beneath the stomata

Tissue Patterns in Stems

Stele is defined as all tissues inside of, but not including, a distinct physiological barrier or boundary layer such as the endodermis

What is Protostele?

-       It is a solid core of conducting tissues in which the phloem usually surrounds the xylem.

Flowering plants develop from seeds that have either one or two “seed leaves,” called cotyledons, attached to the embryonic stems.

Flowering plants that develop from seeds having two cotyledons are called dicotyledons (dicots)

While those developing from seeds with a single cotyledon are called monocotyledons (monocots)

Herbaceous Dicotyledonous Stems

-       In general, plants that die after going from seed to maturity within one growing season (annuals) have green, herbaceous (nonwoody) stems.

Monocotyledonous Stems

-       Monocot stems are a source of commercially important fibers.

Procambium

-       The procambium produces only primary xylem and phloem, but later, a vascular cambium arises between these two primary tissues and adds secondary xylem and phloem to the vascular bundles.

Cambium

-       In some plants, the cambium extends between the vascular bundles, appearing as a narrow ring, producing not only the conducting tissues within the bundles but also the parenchyma cells between them.

Woody Dicotyledonous Stems

-       In the early stages of development, the primary tissues of stems of young herbaceous dicots, woody dicots, and cone- bearing trees are all arranged in a similar fashion.

Seasonal Wood Production

-       In temperate climates, trees produce wood seasonally, resulting in spring wood and summer wood.

Annual rings

-       One year's growth of xylem is called an annual ring.

Vascular Cambium

-       The vascular cambium produces more secondary xylem than it does phloem.

Increment borer

-       It is not necessary to cut down a tree to determine its age.

Specialized Stems

-       Rhizomes are horizontal stems that grow below veal scale- ground, often near the surface of the soil. Adventitious roots are produced all along the rhizome, mainly on the lower surface.

-       Runners are horizontal stems that differ from rhizomes in that they grow aboveground, generally along the surface, they also have long internodes.

-       Stolons are similar to runners but are produced beneath the surface of the ground and tend to grow in different directions but usually not horizontally.

-       Tubers are thickened parts of plants that store nutrients. They help plants survive winter and support new growth.

-       Bulbs are large buds made up of many fleshy leaves, with a small stem at the bottom.

-       Corms look like bulbs but are mostly made of stem tissue, with only a few thin, papery leaves on the outside.

Cladophylls

-       cladophylls (cladodes) are stems that resemble leaves in function and appearance, arise from the axils of a shoot, and have determinate growth (stop growth after reaching a certain size).

Wood and Its Uses

-       Wood is a porous and fibrous structural tissue found in the stem and roots of trees and other woody plants.

-       It has been used for thousands of years for both fuel and as a construction material.

-       It is an organic material, a natural composite of cellulose fibers (which are strong in tension) embedded in matrix of lignin which resists compression.

Density - the effects of the amount of moisture that wood can hold, its shrinkage and swelling, and its mechanical and other properties.

Durability - Wood durability refers to its ability to withstand decay from organism and insects. Seasoning reduces moisture for decay organisms to survive.

TYPES OF SEWING

1. Plainsawing - refers to lumber cut tangent to annual rings or growth or, in commercial practice, cut with annual ring at an angle 0 degree to 45 degree.

2. Quartersawing- refers to wood cut radially to the annual of growth parallel to the rays or in commercial practice, cut with the annual growth rings at an angle 45 degree to 90 degree.

Knots

Knots are lost branches covered by new wood rings from the trunk`s cambium. They are found in old logs due to insufficient light.

Different Kind of Woods and Its Uses;

Hemlock. This relatively soft, light, straight-grained, resin-free wood, with its uniformly long fibers, is becoming one of the most important species for paper pulp. It is also used for structural lumber and plywood, and for boxes, barrels, and concrete forms.

Red Spruce. A favorite for violin sounding boards because of its high resonant qualities. A softwood, it is easy to work, and is light in relation to its strength and stiffness. These qualities also make it eminently suitable for ladder rails, canoe paddles, and oars.

White Oak. Makes good barrels because the wood is resilient, durable, and impermeable to liquids. This hardwood, which is about twice as dense as white pine, has many other uses ranging from flooring to fine cabinet work.

White Pine. A softwood widely used in home construction and for virtually everything from masts and matches to boxes and crates. Its soft, uniform texture and straight grain cuts easily in every direction, polishes well, and warps or swells little.

Hard Maple. In bowling pins and flooring for bowling alleys its uniform texture and hardness result in resistance to abrasion. The Romans used it for spears and lances. We turn it on lathes to make spools, bobbins, cue sticks, and croquet balls.

Black Walnut. A choice hardwood for fine furniture and interior paneling, because of the beauty of the heartwood grain, its ability to stay in place after seasoning, and its good machining properties. It is harder than oak and shock-resistant.