Chapter 34 Flashcards
The thin, transparent layer of wax that covers the leaf surface is a compromise between the needs to optimize ___ and to minimize ___ ___
The thin, transparent layer of wax that covers the leaf surface is a compromise between the needs to optimize photosynthesis and to minimize water loss
Simple leaves
single blade
compound leaves
having a blade divided into two or more leaflets
Leaves are arranged on a stem in one of three ways:
- alternate
- opposite
- whorled
Alternate arrangement of leaf
On leaf at each node
Opposite arrangement of leaf
two leaves on each node
Whorled arrangement of leaf
three or more leaves at each node
leaf blades may have ___ or ___ venations
leaf blades may have parallel or netted venations
netted veins can be
pinnately netted or palmately netted
pinnately netted
major veins branching off in succession along the midvein
palmately netted
major veins radiating out from one point
Most cells in the ___ and ___ epidermis of the leaf lack ___ and are relatively transparent
Most cells in the upper and lower epidermis of the leaf lack chloroplasts and are relatively transparent
Epidermal cells of the leaf secrete
a waxy cuticle that reduces water loss from exterior walls
many leaves are covered in ___
many leaves are covered in trichomes
trichomes
the “hairs” that are extensions of the epidermal cells on a leaf
some help reduce water loss, secrete stinging irritants to deter herbivores or excrete excess salts
leaf epidermis contains ___ for gas exchange
leaf epidermis contains stomata for gas exchange
each stomata is flanked by two ___ cells which ___ and ___ the stomata
each stomata is flanked by two guard cells which open and close the stomata
guard cells are associated with special subsidiary cells that provide a reservoir of ___ and ___
guard cells are associated with special subsidiary cells that provide a reservoir of water and ions
leaf mesophyll
photosynthetic ground tissue of the leaf sandwiched between the upper and lower epidermis
mesophyll cells
parenchyma cells packed with chloroplasts, loosely arranged. with many air spaces between them that facilitates gas exchange
Palisade mesophyll
columnar cells in the upper layer
specialized for light capture
may be organized into one, two, three, or more layers
spongy mesophyll
irregularly arranged cells in the lower layer
loosely packed cells allow diffusion of gases within the leaf; particularly co2
no ___ cell is more than two or three cells away from a vein
no mesophyll cell is more than two or three cells away from a vein
bundle sheath
one or more layers of nonvascular cells surround the larger veins and make up the bundle sheath
bundle sheath may have bundle sheath extensions
support columns
extend through the mesophyll form the upper to lower epidermis
Eudicot leaf
Broad, flattened blade with a petiole
netted venation
guard cells shaped like kidney beans
monocot leaf
narrow blade; base of the leaf wraps around the stem
parallel venation
some have guard cells shaped like dumbbells
leaf ___ is relatively transparent and allows light to penetrate to mesophyll
leaf epidermis is relatively transparent and allows light to penetrate to mesophyll
stomata permit ___ to diffuse in, and ___ produced to diffuse out of the leaf
stomata permit CO2 to diffuse in, and oxygen produced to diffuse out of the leaf
Veins supply ___ tissue with water and minerals and carry dissolved sugar produced during photosynthesis to all parts of the plant
Veins supply photosynthetic tissue with water and minerals and carry dissolved sugar produced during photosynthesis to all parts of the plant
stomata are adjustable ___-usually open during the ___ when CO2 is required for photosynthesis and closed at ___
stomata are adjustable pores-usually open during the day when CO2 is required for photosynthesis and closed at night
opening and closing of stomata are controlled by two ___ cells that surround each pore
opening and closing of stomata are controlled by two guard cells that surround each pore
When water moves into guard cells, they become ___ and bend, producing a ___
When water moves into guard cells, they become turgid and bend, producing a pore
When water leaves the guard cells, they become ___ and the ___ closes
When water leaves the guard cells, they become flaccid and the pore closes
Additional factors that affect stomata
- Low concentration of CO2 in the leaf induces stomata to open
- prolonged draught, stomata remain closed
- hormonal control, mostlu by abscisic acid
- internal biological clock
Guttation
typically occurs in low-growing plants at night, when stomata are closed but water continues to move into the roots by osmosis
deciduous plants
change color and abscise leaves in autumn
leaf abscission is initiated by
plant hormones
