Chapter 5
Basic types of cell tissues
cells have only a primary wall that remains thin
Parenchyma Tissue - a mass of parenchyma cell
Chlorenchyma cells are parenchyma cells involved in photosynthesis
parenchyma tissue that conducts nutrients over a long period of time is phloem
some only function by dying at maturity
Collenchyma
primary cell wall that is thin in some places and is thicker in others
exhibits plasticity, the ability to be formed and deformed by pressure
because they are thick they require more glucose
Sclerenchyma
has both a primary wall and a thick secondary wall
are elastic
developed from parenchyma cells in mature organs after they have stopped growing
Conducting slerenchyma or mechanical sclerenchyma
External Organization of stems
All flowering plants have the same basic stem organization
Nodes are where leaves are attached
Internodes are the spaces between nodes
stem area just above where the leaf attaches is the leaf axil
a miniture shoot with a dormant aqpical meristem and several young leafs is an auxiliary bud
bud is covered in a waxy corky bud scales
the extreme tip is called the terminal bud
Rhizomes are fleshy horizontal stems that allow a plant to spread underground
tubers are horizontal like rhizomes
Internal organization
outermost tissue is epidermis
outer tangential walls are covered with cutin which makes walls impervious to water
a single layer of parenchyma cells
prevents water loss #
then builds up the cuticle
the epidermis contains a pair of cells that regulate gas exchange called guard cells
which has a stomatal pore between them , then these constitute to form a stoma
cortex is the interior to the epidermis
some epidermal cells elongate outward and become tichomes, also called hairs #
some cortex cells contain large crystals of calcium oxylate or deposits of silica
Vascular tissues
two types of vascular tissues
xylem - which conducts and winerals and phloem - which distribute sugars and minerals
xylem - two types of conducting cells. tracheids and vessel elements #
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Phloem - two types of conducting cells, sieve cells and sieve tube member
sieve pores occur clustered
Vascular bundles
xylem and phloem occur together in vascular bundles located just interior to the cortex
Stem growth and differentiation #
stems grow longer by creating new cells at their tips, in regions known as shoot apical meristems
the region just below the apical meristem is called the subapical meristem
