Nutrition in Flowering Plants Flashcards
why do leaves have a large flat surface area compared to volume?
to obtain maximum amount of light for photosynthesis
why are leaves thin?
for atmospheric carbon dioxide to rapidly reach the inner cells of the leaf
how are leaves generally arranged and why are they arranged like this?
- leaves grow in pairs in a regular alternate arrangement
- leaves do not block one another from receiving sufficient light
function of the leaf stalk?
to hold the leaf blade away from the stem so that it can obtain sufficient sunlight
another name for the leaf stalk is called?
petiole
what is the structure of the upper epidermis?
- a single layer of closely packed cells
- covered by a waxy and transparent cuticle
what is the function of the upper epidermis?
- the waxy cuticle reduces water loss by evaporation of water from epidermal cells
- transparent for light to pass through to the palisade layer
structure of the palisade mesophyll?
- one or two layers of closely packed, long and cylindrical cells
- contains numerous chloroplasts containing chlorophyll (highest concentration)
function of the palisade mesophyll?
it is the main site of photosynthesis
structure of the spongy mesophyll?
- irregularly shaped cells that are loosely packed
- due to their arrangement, there are intercellular air space between them
- covered by a thin film of moisture
- fewer chloroplasts than the palisade mesophyll
function of the spongy mesophyll?
- intercellular air spaces allow for rapid diffusion of carbon dioxide and oxygen in and out of mesophyll cells
- some photosynthesis occurs here
structure of the vascular tissue?
- veins in the leaf that contain xylem and phloem tissues
- xylem consists of lignified hollow vessels
- phloem consists of sieve tubes and companion cells
function of the vascular tissue?
- veins provide necessary support for the leaf
- xylem transports water and dissolved mineral salts from the roots to mesophyll cells
- phloem transports synthesised glucose and amino acids away from the leaf to the rest of the plant
structure of the lower epidermis?
- layer of closely packed cells
- covered by waxy transparent cuticle
- has many stomata present
function of the lower epidermis?
- stomata allows for gaseous exchange between intercellular air spaces and the surroundings
- waxy cuticle prevents water loss and is transparent for light to pass through to reach mesophyll cells
structure of the stomatal pores?
- minute openings
- surrounded by a pair of specialised guard cells that contain chloroplast
(more stomata can be found on the lower epidermis)
function of the stomatal pores?
- in the presence of light, guard cells open the stomata for carbon dioxide to diffuse in and oxygen to diffuse out of the leaf
- controls the rate of water loss
characteristics of guard cells?
- bean shaped in surface view
- contain chloroplast to photosynthesise
- can control the rate of diffusion of gases by controlling the size of stomata
- cell wall near the stoma is thicker than the rest of the guard cell
characteristics of epidermal cells?
- irregularly shaped
- do not have chloroplasts
- protect the inner regions of the leaf
- uniform thickness in cell wall
what happens to the guard cells when light is present?
- chloroplasts in the guard cell photosynthesise using light energy to synthesise glucose
- glucose is metabolised to pump potassium ions from neighbouring epidermal cells into the guard cells
- water potential of the cell sap decreases, hence water from neighbouring epidermal cells enter the guard cell through osmosis
- guard cells swell and become turgid
- since guard cells has a thicker cellulose cell wall on the inner side of the cell wall, they swell curve around the open stoma
what happens to the guard cells when light is absent?
- the accumulated potassium ions diffuse out the guard cells
- water potential in the guard cells increase and water leaves through osmosis
- guard cells become flaccid and the stomata close
what happens to the guard cells when temperature is high?
- there is an excess evaporation of water
- guard cells become flaccid
- stomata are closed
why does the stomata close on hot temperatures?
to prevent the excess water loss from the leaf
word equation of photosynthesis?
water + carbon dioxide (light + chlorophyll) –> glucose + oxygen
characteristics of photosynthesis?
(hint: 7)
- anabolic process
- energy is stored in glucose
- releases oxygen
- uses water and carbon dioxide
- increases dry mass
- occurs in chloroplast
- only occurs in the presence of chlorophyll and light
characteristics of aerobic respiration?
(hint: 7)
- catabolic process
- energy is turned into ATP for energy requiring processes
- uses oxygen
- releases water and carbon dioxide
- decreases dry mass
- occurs in mitochondrion
- occurs in all living organisms
similarities between photosynthesis and respiration?
- both are metabolic processes
- involve the exchange of carbon dioxide and oxygen gases
- requires organelles
what happens to the glucose from photosynthesis?
- glucose formed is used immediately by plant cells for tissue respiration to release energy for cellular activities
- excess glucose is turned into starch for storage in the chloroplast
- glucose is used to form cellulose cell wall
- glucose can also be turned into sucrose and transported via the phloem to storage organs
- glucose at the storage organs are converted to starch
- glucose forms fats to be used in cellular respiration to form new protoplasm (eg. cell membrane)
- glucose reacts with nitrates to form amino acids that combine to form proteins
- amino acids can be used to build new protoplasm
what are 4 factors that can affect the rate of photosynthesis?
- temperature
- light intensity
- concentration of carbon dioxide
- light colour
what colours are absorbed most effectively by chlorophyll?
blue and red
why is temperature a limiting factor of the rate of photosynthesis?
photosynthesis is an enzyme-controlled reaction and is enzyme-sensitive
different plants thrive at different optimum temperatures, and it can be assumed that the rate of photosynthesis doubles every 10 degrees celsius increase
