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Chapter 7 Mind Map, Leave and Natural Selection, Venation Patterns,…
Chapter 7 Mind Map
Morphology and Anatomy of Other Leaf Types
succulent leaves
adaptation that allows better survival in desert habitats
succulent leaves
thick
fleshy
reduces surface-to-volume ratio
favors water conservation
cylindrical or spherical leaf shape
mesophyll
contains very few air spaces
reduces water loss through stomata
transparent
allows light to travel further into leaf
sclerophyllous foliage leaves
leaves
must produce more sugars than are used
sclerenchyma is limited in foliage leaves
plant needs extra energy for leaf production
leaves tend to be soft, flexible, and edible
have evolved to be perennial in some species
perennial nature allows for resistance to
animals
fungi
freezing temperatures
ultraviolet light
sclerenchyma
present in
a layer just below the epidermis
in bundle sheaths
cuticle
waxes
leaves of conifers
almost all species of conifers
leaves are sclerophylls
have a thick cuticle
epidermis and hypodermis have thick walls
leaves contain unpalatable cuticles
conifer leaves
always simple
never compound
only have a few forms
mostly perennial
conifer needles
can be short
can be long
occur in all pines, firs, and spruces
can live for at least five years
bud scales
one of the most common leaf modifications
primary role is protection
spines
have no blade and are needle-shaped
dead and dried out lignin makes them hard and resistant to decay
tendrils
act like another form of leaf
can grow indefinitely
can sense solid objects and curl around them
no lamina forms in tendrils
leaves with kranz anatomy
distinct leaf anatomy that occurs in plants with C4 photosynthesis
leaves
lack palisade parenchyma
lack spongy mesophyll
have prominent bundle sheaths which are composed of large chlorophyllous cells
cells surrounding bundle sheaths have Kranz anatomy
insect traps
ability to trap and digest insects has evolved in multiple families
insectivory happens most in environments with poor nitrates and ammonia
leaves
are similar to many foliage leaves
thin and parenchymatous
capable of photophosynthesis
numerous stomata and vascular bundles
mesophyll contains aerenchyma and chlorenchyma
External Structure of Foliage Leaves
parts of a leaf
leaf blade
also called lamina
flat, light-harvesting portion
dorsal surface
also called abaxial side
blade's lower side
ventral surface
also called adaxial side
blade's upper side
petiole
stalk
holds blade out into the light
leaves that are long and narrow are called a sessile leaf and do not have a petiole
many monocots form a sheathing leaf base and do not have a petiole
leaf blade
simple leaf blade
blade has just one part
compound leaf blade
blade is divided into several individual parts
has many small blades (leaflets)
each leaflet is attached by a petiolule
petiolule is attached to the rachis (an extension of the petiole)
vein
bundles of vascular tissue
functions
distribute water from stem into leaf
collect sugars produced by photosynthesis
carry sugars to the stem or other storage
reticulate venation
netted pattern
occurs in basal angiosperms and eudicots
parallel venation
side-by-side pattern
occurs in monocots
leaf base
abscission zone
usually in the petiole
cells are involved in cutting the leaf off
happens when the useful life of the leaf is over
leaf scar
corky, protective scar tissue
occurs when a leaf falls off
Internal Structure of Foliage Leaves
epidermis
epidermis is the outer layers of cells
water lost through the epidermis is called transpiration
the epidermis must
be reasonably waterproof
be translucent
allow entry of carbon dioxide molecules
leaf and stem epidermises are similar
large percentage of flat, tubular cells
ordinary epidermal cells
guard cells
trichomes
stomata
located mainly in the lower epidermis
some species have no stomata in the upper epidermis
spores do not often get into plant as stomata are rare on the upper epithelial surface
stomata are located in crypts which allow for better water retention
hair on stomata prevent rapid air movement and slow water movement
mesophyll
ground tissues interior to the epidermis
palisade parenchyma
a layer of cells along the upper surface of most leaves
also called palisade mesophyll
the main photosynthetic tissue in plants
cells are separated slightly - most of surface area is exposed
large surface area gives maximum area for CO2 dissolution
often only one layer thick
spongy mesophyll
lower portion of the leaf
composed of open, loose aerynchyma
permits CO2 to diffuse rapidly into the stomata
occurs either in the middle or is lacking
vascular tissues
located between the palisade parenchyma and spongy mesophyll
eudicot leaf typically has
one large midrib (or midvein)
lateral veins that stem from the midvein
minor veins which stem from lateral veins
minor veins
most important for releasing water from xylem
loads sugar into phloem
midrib and lateral veins
used mainly for conduction
always contain
primary xylem on the upper side
primary phloem on the lower side
both conduct and support the leaf blade
probably have a bundle sheath around vascular tissues
larger veins have a bundle sheath extension
petiole
may be tiny, but can be massive in
palms
rhubarb
celery
water lilies
area in plant
considered to be part of leaves
transition between stem and lamina
often contains less stomata and trichomes
leaf traces
one, three, five or more vascular bundles
branch from stem vascular bundles and branch towards petiole
stipules
two small flaps at the bottom of the petiole
functions
may protect young apical meristem
can contribute to photosynthesis
may die early
Concepts
leaves
natural selection has resulted in many different types
large, flat, green structures involved in photosynthesis
functions of types of leaves
protection - bud scales and spines
support - tendrils
storage - fleshy leaves of bulbs
nitrogen procurement - trapping and digesting insects
shoot system
contains both stems and leaves
demonstrates
division of labor
integration of distinct plant organs
Initiation and Development of Leaves
basal angiosperms and eudicots
leaf primordium
location of leaf growth
at the base of the meristem
leaf primordium grows out from the protoderm
extends up into a narrow cone and becomes taller than the apical meristem
cells during this early growth
leaf protoderm
leaf ground meristem
all cells are meristemic
have dense cytoplasm and small vacuoles
perennial plants
leaves are initiated in the summer or autumn before maturation
bud opens in the spring and flowers
short dormant period during winter
primordial leaves expand rapidly
little or no mitosis or cell division will occur
the lifecycle of annual plants is similar to that of perennial plants, just shorter
monocots
leaves
leaves are initiated by the expansion of some shoot apical meristem cells
primordium grows to form a cylinder around the shoot apical meristem
tubular portion forms a sheathing leaf base
original conical leaf primordium becomes lamina
next leaf will begin growing in previous leaf sheath
lamina
can become broad and expanded
can become linear and strap-shaped
grows from meristem located at its base
attaches to the top of the sheathing leaf base
meristematic cells remain active mitotically
this type of regeneration is not possible in most leaves
Different Types of Leaves
Vein Patterns and Distributions
Lamina in Other Plants
Mesophyll in Leaves
