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what is photosynthesis
a chemical reaction that produces plant food (glucose)
what do plants need for photosynthesis
water
sunlight
carbon dioxide
what are the products
glucose and oxygen
why are glucose and oxygen needed
for respiration (release of energy)
how are gases exchanged at the leaf
carbon dioxide diffuses into the leaf, because there is a higher concentration of it outside than inside.
oxygen is produced in photosynthesis and diffuses out of the leaf through the stomata
how is a leaf adapted
petiole - used to move the leaf towards the sun
chloroplasts - site of photosynthesis
stomata - allow gases in and out
thin - diffusion happens easily
xylem and phloem carry water and glucose
photosynthesis word equation
carbon dioxide + water → glucose + oxygen
photosynthesis balanced equation
6CO2 + 6H20 → C6H12O6 + 6O2
what is the palisade mesophyll
very thin so gasses can pass through easily
lots of chloroplasts to absorb light energy
what is the waxy cuticle
prevents water loss
transparent to let light through
large surface area
what is the spongy mesophyll
air spaces allow gases to be absorbed or for them to leave
what is the guard cell
control the stomata
turgid - firm - open stomata
flaccid - soft - closed stomata
what is the stomata
open and close to let gases in and out
what is glucose needed for and where is it stored
immediate energy source for respiration
to make cellulose (cell wall)
starch because its soluble
stored in sucrose (fruit)
stored in fats (seeds)
growth and repair
algal balls practical vairables
independent - distance away from light source
dependent - PH
control - volume of indicator, starting PH, number of algal balls
xylem cells
dead cells
carries water and minerals
cell wall made of lignin
no cytoplasm
one way
phloem cells
living cells
carries glucose to growing parts or storage organs
cell wall made of cellulose
permeable cell walls
bidirectional
transpiration
water is absorbed by roots, travels through plant, evaporates from surface
occurs in xylem cells
translocation
occurs in the phloem cells
carrying glucose from one place in the cell to another
when is a potometer used to measure
the rate of transpiration
what are the 4 factors that may increase the rate on transpiration
humidity
wind
sunlight
temperature
how are plants in deserts adapted
small surface area:volume ratio
cacti have spines instead of leaves to prevent water loss
small leaved or folded leaves to reduce evaporation
marram grass
waxy cuticle - reduces water loss through evaporation
sunken stomata - reduce water loss through transpiration
rolled leaf - to protect the stomata from the wind
plant hormones
a chemical produced in plants to control their response to stimuli
auxins are plant hormones responsible for growth responses
auxins are produced in the shoot tips and root tips
what are the three things a plant will react to
water
light
gravity
what is tropism
the stimuli
phototropism
the response to light
hydrotropism
the response to water
geotropism/gravitropism
the response to gravity
negative tropism
growing away from the stimulus
positive tropism
growing towards the stimulus
stimulus growth in shoots
the hormones collect on the lower side
it grows more and bends upwards away from the force of gravity
retards growth in roots
hormones collect on the lower side
slows down growth
root grows downwards towards gravity
gibberellins
controls flower and fruit foundations
produce seedless fruit
controls seed germination
improves fruit quality
ethene
ripening hormone
influences growth by controlling cell division
fruit is picked when unripe to prevent damage
ethene gas is added to start ripening process
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