lecture 12 Flashcards
what are the two major functions of leaves?
photosynthesis and transpiration/gas exchange
what are some other functions of leaves?
- regulate water content
- storage
- chemical secretion to attract or deter animals
- protection
- generation and signaling of hormones
- reproduction
- nutrition
where are leaf primordia generated?
near the shoot apical meristem
what are leaf veins made up of?
xylem and phloem
what are leaf veins responsible for?
carrying water and other materials to the leaf and away from the leaf
why are leaves flat?
- more surface area to photosynthesize
- gas exchange
- transport
-vein organization
what are the functions of the dermal tissue in leaves?
- protection
- limit water loss
- facilitate gas exchange with the environment (stomata)
what does the dermal tissue in leaves consist of?
epidermis and guard cells
what does the vascular tissue in leaves consist of?
xylem and phloem
what are the functions of the vascular tissue in leaves?
- supply water and nutrients
- export of photosynthate
what are the functions of the ground tissue in leaves?
- photosynthesis
- site of gas exchange
- storage of carbohydrates, water, and nutrients
- overwintering
what does the ground tissue in leaves consist of?
parenchyma cells that make up the mesophyll (palisade and spongy mesophyll)
what are the parenchyma cells that make up leaf mesophyll responsible for?
capturing light energy and using it to synthesize carbohydrates
palisade mesophyll vs spongy mesophyll
palisade mesophyll:
- right angles to adaxial surface of the leaf
- long, thin, tightly packed
spongy mesophyll:
- irregularly spaced and sized
- many air spaces for gas exchange via diffusion
how do guard cells regulate the rate of water loss?
by changing the size of the central pore
what did Theodore Engelmann show? 1
not all wavelengths of light are as efficient at driving photosynthesis
what are the two separate sets of reactions that occur during photosynthesis?
light-dependent (electron transfer)
light-independent (enzymatic reactions)
what do intact chloroplasts do?
absorb light energy and synthesize carbohydrates
what do isolated thylakoids do?
generate O2 and ATP, but no sugars
which pigments are present in photosystem I?
chlorophyll a and chlorophyll b
what is the reaction center of photosystem I?
P700
which pigments are present in photosystem II?
chlorophyll a, chlorophyll b, and carotene
what is the reaction center of photosystem II?
P680
photosystem I vs photosystem II
photosystem I:
- greater proportion of chlorophyll a than b in light harvesting complex
- sensitive to longer wavelength light
photosystem II:
- equal amounts of chlorophyll a and b
- light-harvesting complex sensitive to shorter wavelength light
why don’t isolated thylakoids synthesize sugar?
can’t run the calvin cycle because the necessary enzymes have been washed away
what are the 3 major steps in the conversion of CO2 to carbohydrate though the calvin cycle?
- carboxylation: addition of CO2 to RuBP
- reduction: reduction of 3-PGA to PGAL (addition of electrons)
- regeneration: reconstituting RuBP from PGAL
