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Structure of Woody Plants (Secondary Xylem: formation that occurs after…
Structure of Woody Plants
Secondary Xylem: formation that occurs after the vascular cambium's secondary growth
Types of wood cells
Axial system
consists of tracheids and trachery elements that conducts watert
consists of fibers, hardness of wood depends upon the fibers it consist
derived from fusiform initials
Radial system
derived from ray initials
Ray parenchyma cell
upright cells: these cells have connection with axial cells
procumbent cells: these cells have no direct contact with the axial cells
Growth ring
a concentric layer of wood, shell, or bone developed during an annual or other regular period of growth
increment of wood added during a single growth period
Heartwood and Sapwood
Heartwood: dead inner wood, usually dark
Main function of heartwood is to support the tree
Sapwood: living, outermost portion of a woody stem, usually lighter in color
brings water and nutrients up from the roots through tubes inside of the trunk to the leaves and other parts of the tree
Reaction wood
found on branches and leaning stems
wood that forms in place of normal wood as a response to gravity where the cambial cells are oriented other than vertically
Secondary Phloem: formed from vascular cambium
shape, size, number match with xylem ray
made by same ray initials
innermost layer, capable of conduction
Axial and radial system
no similar arrangement
Axial system
conduction up and down the stem/root
angiosperms
conifers
fibers and non conducting parenchyma
sieve tube/ sieve cells conduct for less than one year
Concepts
derived from the meristem
Primary tissues
Primary plant body
in woody plants
additional tissues produced in stems/roots
new tissues
wood and bark
secondary xylem
secondary phloem and cork
Herbs
only body that develops
Secondary tissues
roses, oleanders, and azaleas
secondary plant body
Sycamores, chestnuts pines, firs
woody plants
taller and wider
disadvantages
low germination time
flight, insects, fungi, harsh environment
perennials
need greater defense
adapt to temperate climate
most don't reproduce for years
if killed b4 reproduction
waste of resources
expensive
energy rich
wood burn readily
Conducting tissues
support increases
photosynthetic capacity increase
seeds production/defensive chemicals increase
must be in good, suitable sites
grow into adults and reproduce
mineral, water-upwards, carbs- downward
important consequences
conducting capacity
needs of leaves and roots
helps with overproduction and water loss
adventitious roots
produced to get sugar/water to new stems
rhizomatous
irises, bamboo, ferns
Provascular tissue: Procambium
Fascicular cambium: cambium that develops within the vascular bundle
Vascular cambium: meristem that produces secondary plant body
Fusiform initials: The fusiform initials are elongated tapering cells that give rise to all cells of the vertical system of the secondary phloem and xylem
axial xylem
axial phloem
cork cambium
cork: composed of phloem, cortex and epidermis. It is the outer layer of bark
Phelloderm: a layer of parenchyma produced inwardly by a phellogen
Ray initials: a cell in the cambium that gives rise to cells of the rays
phloem rays
xylem rays
Pith: soft and spongy tissue
Interfascicular cambium: cambium that develops between the vascular bundle
