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biology > nutrition in plants A > Flashcards

nutrition in plants A Flashcards

1
Q

structural adaptations of leaf blade + how it helps with photosynthesis

A

large flat surface – obtain max amount of light for photosynthesis

thin – allows atmospheric CO2 to rapidly reach inner leaf cells

leaf stalk – holds leaf blade away from stem so it can recieve sufficient light and air

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2
Q

possible arrangement of leaves

A
  1. in pairs
  2. single but alternating

–> prevent leaves blocking one another from receiving sufficient light

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3
Q

parts of the inside of a leaf

hint : 6

A
  1. upper epidermis
  2. palisade mesophyll tissue
  3. spongy mesophyll tissue
  4. vascular bundle
  5. lower epidermis
  6. stomata
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4
Q

structure of the upper epidermis

A
  • single layer of closely packed cells
  • covered on outside by waxy, transparent cuticle
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5
Q

function of upper epidermis

A
  • waxy cuticle prevents water loss from evaporation of water from epidermal cells
  • transparent to allow light to pass through
  • protects inner region of leaf
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6
Q

structure of palisade mesophyll

A
  • 1 or 2 layers of closely packed, long and cylindrical cells below upper epidermis
  • contains highest concentration of chloroplasts (more light can be absorbed at upper surface of leaf)
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7
Q

function of palisade mesophyll

A

main site of photosynthesis

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8
Q

structure of spongy mesophyll

A
  • irregularly shaped cells
  • fewer chloroplasts than palisade mesophyll
  • cells covered with thin film of moisture
  • loosely packed, containing intercellular air spaces
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9
Q

function of spongy mesophyll

A
  • intercellular air spaces allow for rapid diffusion of CO2 and O2 in and out of mesophyll cells
  • some photosynthesis occurs here
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10
Q

structure of vascular bundle

A
  • xylem and phloem are grouped together to form the vascular bundle
  • xylem contains lignified hollow tissue
  • phloem contains sieve tubes and companion cells

note : when looking at diagram, XYLEM on TOP, PHLOEM at BOTTOM

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11
Q

function of vascular bundle

A
  • supports the leaf
  • xylem transports water and dissolved mineral salts from roots to mesophyll cells
  • phloem transports synthesised sucrose and amino acids from leaves to rest of the plant
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12
Q

structure of lower epidermis

A
  • single layer of closely packed cells
  • covered on outside by waxy, transparent cuticle
  • many stomata present
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13
Q

function of lower epidermis

A
  • waxy cuticle prevents water loss from evaporation of water from epidermal cells
  • transparent to allow light to pass through
  • stomata allow gaseous exchange between interceullar air spaces within spongy mesohyll and surrounding atmosphere
  • protects inner region of leaf
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14
Q

structure of stomata

A
  • minute openings surrounded by a pair of specialised guard cells contaning chloroplasts
  • more stomata are found on the lower epidermis (Lower surfaces are not directly exposed to sun. This tends to reduce excessive water loss.)
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15
Q

function of stomata

A
  • when light is present , stomata are opened by guard cells, allowing gaseous exchange
  • controls rate of water loss
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16
Q

what happens to stomata in the presence of sunlight

A

1) chloroplasts in guard cell photosynthesise using energy from light to synthesise glucose

2) water potential of guard cell sap is decreased by:
* increase in glucose concentration
* glucose is metabolised to release chemical energy via respiration to pump K+ from neighbouring epidermal cells into guard cells (active transport)

3) water from neighbouring epidermal cells enter guard cells via osmosis, they swell and become turgid

4) guard cells have a thicker cell wall near the stoma, hence the swollen guard cells curve around the stoma, opening it

17
Q

what happens to stomata in the absence of sunlight

A
  1. K+ accumulated in guard cells during the day diffuses out of the cells
  2. increases water potential of guard cells, water leaves via osmosis
  3. guard cells become flaccid, stoma closes
18
Q

what happens to stomata on very hot days

A
  1. strong sunlight, excess evaporation of water
  2. guard cells become flaccid, closing stoma to prevent water loss
18
Q

word equation for photosynthesis

A

water + carbon dioxide –light, chlorophyll–> glucose + oxygen

19
Q

chemical equation for photosynthesis

A

6H2O + 6CO2 –light, chlorophyll–> C6H12O6 + 6O2

20
Q

why is the leaf colored green?

A
  • contains chlorophyll, a green pigment
  • chlorophyll absorbs red and blue light the best but reflects most of green light
21
Q

differences in aerobic respiration and photosynthesis

A
  1. AEROBIC RESPIRATION – catabolic process, breakdown of carbohydrates into simple inorganic molecules
    PHOTOSYNTHESIS – anabolic process , formation of carbohydrates from simple inorganic molecules
  2. AEROBIC RESPIRATION – energy incorporated into ATP
    PHOTOSYNTHESIS – energy stored in glucose
  3. AEROBIC RESPIRATION – results in decrease in dry mass
    PHOTOSYNTHESIS – results in increase in dry mass
22
Q

similarities of photosynthesis and aerobic respiration

A
  1. metabolic processes
  2. require mechanisms for gaseous exchange (alveoli, stoma)
  3. require organelles (mitochondria, chloroplasts)
23
Q

uses of photosynthesised glucose

A
  1. used immediately for tissue respiration to release energy for cellular activities
  2. used to form cellulose cell walls
  3. excess glucose converted into sucrose and transported via phloem to storage organs where it is then converted into starch/other storage compounds
  4. used to form fats for cellular respiration or formation of new protoplasm
  5. react with nitrates (mineral salts) to form amino acids, amino acids combine to form proteins. amino acids used to form new protoplasm or stored as proteins
24
Q

what factors is the rate of photosynthesis affected by?

hint : 4

A
  1. light intensity
  2. light color (NOT LIMITING)
  3. temperature
  4. concentration of CO2
25
Q

how does light intensity affect the rate of photosynthesis?

A

as light intensity increases, rate of photosynthesis increases

26
Q

how does light color affect rate of photosynthesis?

A
  • blue and red lights cause highest rates of photosynthesis (as they are absorbed the most by chlorophyll)
  • green light results in the lowest rate of photosynthesis
27
Q

how does concentration of CO2 affect rate of photosynthesis?

A

as CO2 concentration increases, rate of photosynthesis increases

28
Q

how does temperature affect rate of photosynthesis?

A
  • photosynthesis is an enzyme controlled reaction
  • rate of photosynthesis doubles for every 10℃ increase
  • different plants grow the best in different optimum temperatures
  • as temperature increases, rate of photosynthesis increases

biology (14 decks)

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