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Chapter 5 (External Organizations of Stems (terms Stem and Shoot are used…
Chapter 5
External Organizations of Stems
terms Stem and Shoot are used interchangebly
Nodes are where leaves are attached
Internodes are the region between nodes
Leaf Axil is the stem area just above the point where a leaf attaches
Bud is covered by small, corky, and waxy bud scales
Bud Scales protect delicate organs inside
Protection
The arrangement of leaves on the stem are called phyllotaxy
Leaves are positioned so they do not shade eachother
Stolons are also called runners
Rhizomes are fleshy horizontal stems that allow a plant to spread underground
Tubers are horizontal like Rhizomes, but they grow for a short period of time
Trunk Is the vertical main shoot
Internal Organization of Stems
Epidermis is the outermost of an herbaceous stem
Guard cells are pairs of cells in the epidermis
The hole in guard cells are stomatal pores
Holes in Guard Cells
Epidermal Tissue
Epidermal cells may elongate outward and become trichomes
Hairs are also called Trichomes
Also Called
The cortex is interior to the epidermis
Vascular Tissue
Xylem
Phloem
Stem Growth and Differentiation
Apical Meristems are regions where the stems can grown longer
Subapical meristem is region just below Apical meristem
Region below
constituting the first xylem to appear is known as protoxylem
Metaxylem can grow into largest of all
Exterior cells mature as protophloem
Cells closest to metaxylem become metaphloem
Protoderm refers to epidermal cells that are in the early stages of differentiation
Provascular Tissues are young cells of xylem and phloem
Ground meristem are young stages of the pith and the cortex
Types of Cells
Collenchyma
has a primary wall that remains thin in some areas but also becomes thick in other areas
Present in elongating shoot tips
They require more glucose for their production because o the thick cell walls
Parenchyma Cells are needed in inner tissues for support
Needed for Support
Sclerenchyma
Third basic type of cell and tissue
Thick primary and secondary walls
Walls are elastic
can be deformed
two types
Conducting
Vessel elements
Tracheids
Mechanical
Sclereids
Fibers
Parenchyma
Only have primary walls that remain thin
The Parenchyma tissue is a mass of Parenchyma cells.
Most common cell and tissue
Chlorenchyma cells are involved in photosynthesis
Some parenchyma cells die at maturity as their function
