PLANT LEAVES Flashcards
elicits the image of foliage leaves
leaf
why do leaves modify
− Protection
− Support
− Storage
− Nitrogen procurement
explain physical and chemical characteristics of stem and leaves
− Leaves are flat and thin for maximum absorption of light and CO2. − Stems support and conduct, so a cylindrical structure is ideal.
limitations on foliage leaves
− Can’t lose excessive amounts of water.
− Can’t allow entry of pathogens.
− Can’t be too nutritious and delicious to animals.
− Can’t act as a sails.
− Must be cheap.
balancing acts between advantages and disadvantages.
adaptations
The flat, light harvesting portion
leaf blade or lamina
The blade’s lower side
dorsal / abaxial
The upper side of the leaf
ventral / adaxial
helps keep leaves from shading each other.
petiole
term for leaves with no petiole
sessile
term for leaves with petiole
petiolate
explain monocot leaf base
Long and tapered monocot leaves have no petiole.
The base wraps around the stem to form a sheathing leaf base.
difference between simple leaf and compound leaf
A simple leaf has a blade of just one part.
A compound leaf has a blade divided into several individual parts.
A compound leaf has many leaflets. − Each is attached by a _____ to an extension of the petiole, the ____.
petiolule
rachis
2 compound leaf types and difference
pinnate - all leafelets attached at the same point
palmate - leaflets attached individually along the rachis
three guidelines to distinguish a simple leaf from a pinnately compound leaf.
− Leaflets never bear buds in the axils of their petiolules.
− The tip of the rachis never has a terminal bud.
− Leaflets are always arranged in two rows, never in a spiral, whorled, or decussate phyllotaxy.
3 advantages associated with compound leaves.
− Leaflets can flex in the wind (or water), minimizing wind resistance and preventing tearing.
− Increased turbulence around leaflets can increase heat removal and CO2 uptake.
− Pests/disease may spread less quickly.
leaf shapes
− Entire (smooth)
− Toothed
− Lobed
− Otherwise modified
what are veins of leaves composed of?
bundles of vascular tissue
eudicot veins vs monocot veins
Eudicot veins occur in a netted pattern of reticulate venation.
Monocot leaves have parallel venation.
found at leaf base, cells here are involved in cutting off the leaf as it becomes useless
abscission zone
forms after abscission when adjacent undamaged cells become corky
leaf scar
water loss through the epidermis
transpiration
when would transpiration become a serious problem
if the soil is so dry that roots cannot replace lost water.
why is the the number of stomata much greater in the lower than in the upper epidermis?
− Reduce water loss (due to sunlight heating the upper leaf surface).
− Prevent fungal spores from penetrating.
Leaf stomata are frequently sunken into epidermal cavities that create a region of nonmoving air
stomatal crypts
how do trichomes affect leaf biology
− Provide shade on the upper surface of the leaf.
− Prevent rapid air movement, slowing water loss from stomata.
− Make walking or chewing difficult for insects.
− Glandular trichomes secrete powerful stinging compounds that deter even large animals.
ground tissues interior to the leaf epidermis are collectively called
mesophyll
mesophyll along the upper surface of most leaves
palisade
mesophyll along the lower portion of the leaf
spongy
where are vascular tissues found in the leaf
between palisade and spongy mesophyll
which has a large midrib? monocot or eudicot
eudicot
xylem is on the upperside and phloem on the lower side, t/f
t
composed of fibers that are arranged around vascular bundles
bundle sheath
larger veins often have a mass of supportive fibers above, below or both -
bundle sheath extension
what are petioles?
the transition between the stem and lamina
the epidermis of petiole contains fewer stomata and trichomes
petiole mesophyll is rather like ______
cortex
in many species of leaves, the petiole bears two small flaps of tissue at its base called ______
stipules
thick and fleshy modified leaves that can survive in desert habitats
favors water conservation
mesophyll transparent so photosynthesis may occur deeper in the leaf
succulent leaves
modified leaves: have sclerenchyma as a layer below the epidermis and in the bundle sheets.
Their hardness makes them highly protected.
Sclerophyllous foliage
small modified leaves that form a tight layer around the stem tip.
− Protect dormant buds in the winter.
− Have short or absent petioles.
− Are often very waxy and tough, some hairy.
− May have a thin, corky bark layer.
bud scales
modified leaves of axillary buds.
− Needle sharp projections.
− They are protective and made primarily of fibers.
− Lignified walls make them hard and resistant to decay
spines
modified leaves whose cells can − Sense contact with objects. − Coil around objects and use them for support grow indefinitely do not photosynthesize
tendrils
occur in plants that have C4 photosynthesis.
− Lack palisade parenchyma and spongy mesophyll.
− Have prominent bundle sheaths composed of large chlorophyllous cells.
− Surrounding each sheath is a ring of mesophyll cells.
Leaves with Kranz anatomy
Plants growing in habitats poor in nitrates and ammonia, evolved insect traps.
− Captured insects are digested as a source of ______
nitrogen
can be classified as either
− Active traps that move during capture
− Passive traps incapable of movement
trap leaves
