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chapter 6 (morphology and anatomy of other leaf types (leaves with kranz…
chapter 6
morphology and anatomy of other leaf types
succulent leaves
sclerophyllous foliage leaves
leaves of conifers
bud scales
tendrils
leaves with kranz anatomy
has a special metabolism with C4 photosynthesis
insect traps
external structure of foliage leaves
dorsal side
lower side
large veins protrude like backbones
also known as the abaxial side
petiole
also known as the stalk
holds the blade out to the sun
some plants do not have petiole
this makes the leaf called a sessile leaf instead of a petiolate
they form a sheathing leaf base
abscission zone
involved in cutting off the leaf when its useful life is over
leaf scar is the corky part in the fall that protects the area the leaf fell off
ventral face
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upper side
smooth
also known as the adaxial side
lamina
also known as the leaf blade
flat, light harvesting portion
leaf blade
simple leaf base has a blade of one part
compound leaf has a blade divided into several individual parts
has many small blades (leaflets)
each attached by a petiolule
this is attached to an extension of the petiole, the rachis
internal structure of foliage leaves
epidermis
flat, thin foliage leaves have a large surface area through which water can be lost
this is called transpiration
can be a serious problem if the soil is so dry the roots cannot replace the water
must be waterproof but translucent
must allow the entry of carbon dioxide
large fat tabular in both stem and leaf
often hairy
contain a coating of cutin and sometimes wax
mesophyll
ground tissues interior to the epidermis
upper surface of most leaves is a layer of cells called the palisade parenchyma (mesophyll)
main photosynthetic tissue of most plants
separated slightly so each cell has the most surface exposed to intercellular spaces
in the lower portion of the leaf is the spongy mesophyll
open, loose aerenchyma that permits carbon dioxide to diffuse rapidly away from stomata into all of the leaf's interior
some have a layer of palisade parenchyma along both leaf surfaces
vascular tissues
between the palisade parenchyma and the spongy mesophyll
midrib (midvein)
lateral veins
minor veins
release water from xylem and load sugar into pholem
involved in conduction
many fibers are arranged in a sheath (called a bundle sheath) around vascular tissues
petiole
can be both small and large
leaf traces branch from from stem vascular bundles and diverge toward the petiole
some species can bear two small flaps of tissue at its base calles stipules, which serve various functions
initiation and development of leaves
basal angiosperms and eudicots
at the base of the meristem, cells interior to the protoderm grow outward, forming a protrusion known as a leaf primordium
extends upward as a narrow cone, growing so rapidly that it becomes taller than the shoot apical meristem
this increases thickness, establishing the bulk of the midrib
this initiates the lamina, that grows a small leaf which develops a mature plant
monocots
are intiated by the expansion of the root meristem, like eudicots
the primordium is more a cylinder and encircles the shoot apical meristem