Leaves and Photosynthesis Flashcards
2 major functions of leaves
photosynthesis and transpiration/gas exchange
where are stems attached to the stem
at the node
dicot leaves are attached via the _______
petiole
compound leaves consist of multiple ________
leaflets
How are monocot leaves attached
the sheath
where are leaf primordia generated
near the shoot apical meristem
leaf veins
made of xylem and phloem
responsible for carrying water and other material to and from the leaf
why are veins arranged how they are
Organized based on how leaves grow. Ex: Grass leaves grow up, so the veins are adapted to grow long and parallel
What does the dermal tissue do (epidermis, guard cells)
protection
limit water loss
facilitate gas exchange with the environment (stomata)
What does the vascular tissue do (xylem and phloem)
supply water and nutrients
export of photosynthate
what does the ground tissue do
photosynthesis
site of gas exchange
storage
what type of cells is mesophyll made of?
parenchyma cells
what does the mesophyll do
capture light energy and use it to synthesize carbohydrates
Characteristics of the mesophyll cell wall and why it is that way
thin cell wall that are generally well hydrated
help facilitate exchange of CO2 and O2
Characteristics of palisade mesophyll
right angles to adaxial surface of the leaf (the top
long, rectangular, tightly packed, thin
Characteristics of spongy mesophyll
irregularly spaced and sized
many air spaces
how does the guard cell regulate the rate of water loss
by changing the size of the central pore
Why is the opening and closing of the stomata considered a balancing act?
at times that photosynthetic activity is highest (high light and temp) means need for more CO2, but is also when water loss is the greatest
why is the rate of water loss greater than CO2 uptake
difference in water vapor concentration between the air and sub-stomatal space is greater that the difference of CO2 inside and outside the leaf
types of mesophyll
palisade and spongy mesophyll
2 different reactions of photosynthesis
light-dependent and light-independent
what does the light-dependent reaction do
electron transfer
what does the light-independent reaction do
enzymatic reactions
what will intact chloroplasts do compared to isolated thylakoids
Intact chloroplasts - will absorb light energy and synthesize carbohydrates
Isolated thylakoids - will generate O2 and ATP, but no sugars
Photosystem 1 pigments and reaction center
chlorophyll a and b
P700
Photosystem 2 pigments and reaction center
Chlorophyll a and b, carotene
P680
Photosystem 1 description
greater proportion of chlorophyll a than b in the light-harvesting complex. Sensitive to longer wavelengths
Photosystem 2 description
equal amounts of chlorophyll a and b, sensitive to shorter wavelengths
light harvesting complex
functional pigment units that act as light traps
why don’t isolated thylakoids synthesize sugars
they are no longer in the stroma, which is needed for the Calvin cycle
3 major steps in the conversion of CO2 to carbohydrate through the Calvin cycle
Carboxylation
Reduction
Regeneration
Carboxylation
addition of Co2 to ribulose 1,5-bisphate (RuBP)
Reduction
reduction of 3-phosphoglycudrate (3-PGA) to glyceraldchyde-3-phosphate (PGAL) through the edition of electrons
Regeneration
reconstituting RuBP from PGAL
Photorespiration
uses O2 instead of CO2 in RuBP
when does photorespiration happen
on bright, hot days when the stomata closes to prevent water loss and generate more oxygen
Why is photorespiration a serious problem
plant has to use energy in order to regenerate CO2 from 2-phosphoglycolate. Generates high energy instead of low energy which damages the cell
how have plants adapted mechanisms to minimize photorespiration
C4 and CAM
How does C4 minimize photorespiration
physically separates rubisco from high O2 and low O2 conditions
How does CAM minimize photorespiration
temporally separates Co2 uptake from hot, dry conditions by taking up CO2 during the night
T/F: leaf structure can be altered depending on environmental conditions such as the amount of light striking a leaf
T
Leaf adaptations: spines
For protection and travel
they don’t photosynthesize and help reduce water loss
Leaf adaptations: water leaves - floating
flexible with large aerenchyma cells
hydrophobic leaf surface
Leaf adaptations: water leaves - submerged
reduced investment in leaf and support
small leaves to maximize surface area for gas exchange and light absorption
Leaf adaptations: needles
reduced water loss and prevents damage in extreme conditions
Leaf adaptations: support - tendrils
spiral growth pattern to look for something to attach to
Leaf adaptations: propagation - plantlets
little plants on edge of leaf
Leaf adaptations: water storage and preventing water loss
minimal air space
some leaves adapted to take up water from the air
Leaf adaptations: nutrition storage
thick leaves that store nutrients
Leaf adaptations: nutrition
leaves that eat things to get nutrients and nitrogen
