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Chapter 6 (External structure of foliage (petiole (stalk of the leaf, most…
Chapter 6
External structure of foliage
leaf blade
also called Lamina
flat part
light harvesting portion
dorsal surface
leaf's lower side
larger veins
protruding veins
also called abaxial side
ventral surface
also called adaxial
rather smooth
petiole
stalk of the leaf
most leaves have them
holds blade into light
prevents shading
helps cool leaf
brings fresh air to surface
helps CO2 diffuse
petiolule is an extension
sessile leaf
no petiole
small
narrow
doesn't shade other leafs
compound leaf
many petals
petals are pretorn
harder to tear
abscission zone
usually in petiole
at leaf base
cuts off leaf
releases enzymes
simple leaf
#
one blade
not pre torn
Sheathing leaf base
#
flexible
no petiole
leaf base wraps around stem
morphology and anatomy of other leaves
succulent leaves
helps plants in deserts
characteristic of crassulaceae
characteristic of portulacaceae
characteristic of aizoaceae
thick and fleshy
favors water conservation
cylindrical leaves
spherical leaves
Sclerophyllous foliage leaves
resistant to uv light
resistant to animals
resistant to fungi
resistant to freezing temps
layer of sclerenchyma
leaves of conifers
thick cuticle
sclerophylls
thick epidermal wall
thick hypodermis wall
contain unpalatable chemicals
always simple leaves
very few forms
mostly perennial
bud scales
most common evolutionary conversion
protects apical meristem
tight layer around stem tip
small
rarely compound
no mechanical wind damage risk
spines
on cacti
modified leaves
modified axillary buds
protects cacti water
no vascular tissue
dead fibers
resistant to decay
tendrils
modified leaf
grow indefinitely
cells sense contact
coils around objects
Internal Structure of foiliage
Epidermis
prevents transpiration
allows CO2 through
made of epidermal cells
has guard cells
has trichomes
upper and lower
mesophyll
ground tissues
interior to epidermis
palisade parenchyma
AKA palisade mesophyll
main photosynthetic tissue
lots of intercellular space
spongy mesophyll
lower portion of leaf
open loose aerenchyma
allows CO2 diffusion
vascular tissue
between palisade parenchyma and spongy mesopyll
mid rib
AKA midvein
lateral vein emerge
branch into narrow minor vein
realesing water from xylem
loading sugar in phloem
primary xylem
bundle sheath around
petiole
small in regular plants
big in others like
palms
rhubarb
celery
water lillies
technically part of leaf
leaf traces
stipules
initiation and development of leaves
leaf primordium
narrow cone
extends upward
grows rapidly
taller than apical meristem
increases in thickness
monocots
initiated by expansion
lamina becomes broad in some
apical meristem
#
creates monocots
primordium becomes a cylinder
example of simple leaf
monocots depend on apical meristems
neither have petiole
