B6 - photosynthesis, leaf structure Flashcards
define photosynthesis
process where plant synthesize carbohydrates from raw materials using energy from light
define chlorophyll
-green pigment in chloroplast which absorbs light energy
word & chemical equation for photosynthesis
(light energy) (chlorophyl) - above arrow
-carbon dioxide + water ————–> glucose + oxygen
-6CO2 + ^H2O -> C6H12O6 + 6O2
why test leaf for starch if leaf has photosynthesised
starch is made up of glucose
method to test leaf for starch & reasons
-put leaf in boiling water for 2 minutes- break down cell membrane, stop enzyme action, easier ethanol penetration
-put leaf in ethanol in water bath until it boils - dissolve chlorophyll, prevent masking for observations
-briefly dip leaf in warm water - soften leaf, allow iodine penetration
-put iodine solution on leaf - shows presence of starch
how to destarch plant
leave in dark for 72 hours
method to test if CO2 is needed for photosynthesis
-destarched leaf in airtight bag with soda lime to absorb CO2
-leaf is brown in starch test
-CO2 is needed for photosynthesis
factors for photosynthesis that can be limiting factors & how
-CO2 - soda lime
-light energy - light intensity
-temp.
-chlorophyll concentration
method to test if light energy is needed for photosynthesis
-put a sheet over destarched leaf
-put under light
-parts covered are brown in starch test, exposed parts are blue - black
-light is needed for photosynthesis
note:
-as limiting factor increases, photosynthesis increases.
-when line is flat, that factor is no longer the limiting factor
uses of carbohydrates & roles
-starch - energy storage in leaves/ roots
-cellulose - make cell walls
-glucose - respiration
-sucrose - stored in fruits & transport sugar in phloem
-nectar - feeds insects in pollination
-lipids - cell membrane & long term energy stores in seeds
-protein (add nitrogen) - growth & repair
-DNA (add nitrogen + phosphate) - genetic material
method for light intensity as limiting factor
-do in a dark room
-aquatic plant in beaker of water & inverted measuring cylinder
-thermometer to measure temp.
-lamp with fixed light intensity & varying distance btw beaker
-tube of water as heat screen to stop temp. going up
-leave plant 10 mins to adjust to conditions
-measure volume of oxygen & time
define compensation point
-when rate of photosynthesis & aerobic respiration are same
-eg. sun rise/ sun set - little light
method for temp. as limiting factor
-aquatic plant in breaker of water & inverted measuring cylinder
-thermometer to measure temp.
-lamp with fixed light intensity & distance btw breaker
-hot plate below beaker to measure change in temp.
-leave plant 10 mins to adjust to conditions
hydrogen carbonate indicator colour for more, normal, less CO2 concentration
more - yellow (carbon dioxide becomes carbonic acid)
normal - orange/ red
less - purple
what indicator is used to investigate gas exchange in plant
hydrogen carbonate indicator - shows CO2 concentration
structures of leaf
-waxy cuticle
-upper epidermis
-palisade mesophyll layer
-spongey mesophyll layer
-vein/ vascular bundle: xylem, phloem
-lower epidermis
-guard cell
-stomata
features adapted for photosynthesis
-thin - rapid gas exchange
-large surface area - max. light absorption
-contain chloroplast - absorb light
-stomata - regulate gas exchange & water loss
waxy cuticles description & functions
-waxy layer
-no cells
-prevent water loss
upper epidermis description & functions
-1 cell thick
-transparent (no chloroplast)
-protective layer & barrier to disease organisms
-allows sunlight to penetrate
palisade mesophyll description & functions
-max light intensity - at top; waxy cuticle & upper epidermis are transparent
-densely packed - max. light absorption
-lots of chloroplast - lots chlorophyll - most photosynthesis
-access to CO2 - near spongey mesophyll air spaces
-next to xylem - brings water from roots
spongey mesophyll description & functions
-loosely packed cells
-lots of air spaces
-few chloroplast
-air spaces btw cells allow gas exchange - CO2 to cells, O2 away from cells
xylem description & functions
-on top of phloem
-larger hollow space
-contains xylem vessesl
-bring water & minerals
phloem description & functions
-below xylem
-contains phloem vessels
-transport sucrose & amino acids away from leaf
lower epidermis description & functions
-no chloroplast
-protective layer
-contains stomata & guard cells
stomata description & functions
-contains chloroplast
-changes shape to open. close
-guard cells regulate stomata opening/ closing; allow CO2 to diffuse in, regulate water vapor loss
-guard cells have chloroplast
nitrate ions use & deficiency causes
-protein synthesis (make amino acids)
-deficiency: stunted growth
magnesium ions use & deficiency causes
-making chlorophyll
-deficiency: yellow leaves
liquid that removes/ absorbs CO2
soda lime
note: waxy cuticle is not a cell
describe path carbon dioxide molecule takes to be part of a glucose molecule
-pass through stomata
-pass through air spaces
-diffuses in cell well, cell membrane, cytoplasm
-used in chloroplast
note: photosynthesis is endothermic reaction - requires energy
formula for light intensity: inverse square law
1 / distance^2
