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Leaves - Coggle Diagram
Leaves
Morphology and Anatomy of Other Leaf Types
Kranz Anatomy
no palisade parenchyma or spongy mesophyll
distinct bundle sheaths=large photosynthetic cells
C4 plants
Insect Traps
areas with low nitrates and ammonia
needed for production of proteins and nucleotides
passive traps
stick insects in place, prevent from leaving
active traps
mechanical movement traps insect
Tendrils
grow indefinitely, sense contact with objects
side touching object stops growth
side away from object continues
causes wrapping coil around object
Spines
modified axillary buds
avascular, cells high in lignin
prevent predation, protects water
Conifers
sclerophylls
thick cuticle
epi-/hypodermis have thick walls
leaves always simple, never compound
needles
scale-like
Sclerophyllous Foliage Leaves
require lots of glucose to be made
leaves persist for 2 or more years
longer lifetime prevents net loss of sugar
thick walls make plant more durable
makes longer leaf cycle possible
Succulent Leaves
desert habitats
thick, low surface area:volume
mesophyll has few air spaces
allows light to be conducted well
Internal Structure of Foliage Leaves
Epidermis
water loss
transpiration
due to large SA w thin membranes
must balance CO2 intake w water loss
stomata
often found on bottoms only
crypts
depressions in which stomata sit
prevention of water loss
antimicrobial protection
trichomes
often some sun protection on upper surface
insect repellant
poisonous glandular trichomes
deter animals from eating
water condensates here
prevents stomatal blockage
coat of cutin and wax
Mesophyll
ranges widely with plant function
interior to epidermis
palisade parenchyma
uppermost surface of leaf
site of most photosynthesis
often 1 layer thick, can be many layers
spongy mesophyll
lower portion of leaf
aerenchyma
allows diffusion of gases
Vascular Tissues
between palisade parenchyma and spongy mesophyll
minor veins are like capillaries in animals
common arrangement
1 midrib/midvein
lateral veins several
many minor veins (most important)
mid and lateral veins conduction
minor veins sugar and water
midrib and lateral veins
primary xylem on upper side
primary phloem on lower
because of their size, they need support
may have bundle sheath
fibers that surround
budle sheath extension
mass of fibers that support and facilitate export of water into mesophyll
Petiole
differences between the two
transition from steam to lamina
tissues variable
stomata and trichomes fewer
mesophyll like cortex
can contain collenchyma if leaf is big
vascular tissues widely variable
leaf traces
stem->leaf vascular bundles
many stem bundles converge
diverge into many more leaf vundles
stipules
protect shoot apical meristem
photosynthesis in baby plants
External Structure of Foliage Leaves
functions
photosynthesis
water retention
microbial resistance
structures
leaf blade
lamina
large, flat portion of leaf
light collection, gas exchange
dorsal surface
abaxial side
veins protude
ventral surface
smooth, upper side
arrangement
simple
1 blade
compound
several blades
leaflets attached by petiolule
attaches to rachis, extension of petiole
prevents tearing from wind or water
petiole
very important structure
stalk
protrudes leaf into light
allows leaf to flutter
gas exchange
insect protection
leaf with no petiole=sessile leaf
grasses often wrap leaves
sheathing leaf base
veins
bundles of vascular tissue
eudicots=netted pattern
reticulate venation
monocots=large with few connections
parallel venation
abscission zone
cells perpendicular to petiole
cut leaf off in deciduous trees
leaf scar forms after shedding
Initiation and Development of Leaves
Basal Angiosperms and Eudicots
produced through activity of shoot apical meristem
leaf primordium
divides rapidly, passes shoot meristem
many trees produce them in fall of year before
become dormant, resume development next spring
Monocots
initiated by shoot apical meristem
leaf primordium
older primordium hoods meristem and younger primordium
develops a tube of leaves
continual growth from core of plant
shoot apical meristem stays in base of plant
allows plant to continually produce leaves
plant survives after grazing or lawnmowers
