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Tissues and the Primary Growth of Stems (Internal Organization of Stems:…
Tissues and the Primary Growth of Stems
Basic types of Cells and Tissues
Collenchyma
Primary wall
Thin in some areas
Unable to hold stem up
Thick in other areas
needs lot of glucose
Only in shoot tips and young petioles
Sclerenchyma
Has primary and thick secondary wall
Almost always lignified
Remain upright
Walls are elastic
Develop from parenchyma cells
Deforming forces
Animals
Snow
Wind
Parenchyma
Primary walls remain thin
Parenchyma tissue
mass of parenchyma cells
most common
Soft leaves, petals, fruits, and seeds
Chlorenchyma
Involved in photosynthesis
thin walls permit pigment
numerous chloroplasts
Transfer cells
Short-distance transport
Stem Growth and Differentiation
apical meristems
new cells at tips
subapical meristem
region just below apical meristem
metaxylem
protoxylem
protophloem
metaphloem
External organization of Stems
Shoot
Stem plus leaves, flowers, or buds
Nodes
leaves are attached
Internodes
Between nodes
Bulbs
Short shoots
Thick fleshy leaves
Trunk
Vertical main shoot
Stem
Axis
Leaf axil
Above point where leaf attaches
Axillary bud
miniature shoot
Phyllotaxy
Leaves on stem
distichous phyllotaxy
leaves in 2 rows
Corms
Vertical thick stems
Rhizomes
Fleshy horizontal stems
allow spreading underground
Tubers
Short period of growth
Bud
Bud scales
modified leaves
terminal bud
apex of each stem
Internal Organization of Stems: Arrangement of Primary Tissues
Vascular tissues
transport nutrients
phloem
distributes minerals and sugars
sieve cells
sieve element
sieve areas
sieve tube
1 more item...
sieve pores
xylem
#
conducts water and minerals
Epidermis
Outermost surface
Outer tangential wall
Cutin
Impermeable
cuticle
Cortex
interior of epidermis
photosynthetic parenchyma
#
homogenous
Vascular bundles
pith
parenchyma similar to cortex
contains xylem and phloem
#
primary phloem
primary xylem
