plant

Question 1

parts of leaf from top to bottom

Answer 1

cuticle, upper epidermis, palisade mesophyll layer (with chloroplasts), spongy mesophyll lAyer (with vascular bundles), lower epidermis, cuticle with stomata

Question 2

cuticle function

Answer 2

Waxy: reduce water loss by evaporation
Transparent: light reaches cells within for photosynthesis

Question 3

upper epidermis function

Answer 3

protect leaf from physical damage

Question 4

palisade mesophyll layer function

Answer 4

more chloroplasts in the upper palisade tissue, more light energy absorbed near leaf surface to be converted to more chemical energy in the manufacture of sugars

Question 5

spongy mesophyll layer function

Answer 5

loosely arranged with air particles to allow rapid diffusion of CO2 and O2 in and out of mesophyll cells

Question 6

petiole (leaf stalk) function

Answer 6

holds leaf in position to absorb maximum light energy

Question 7

lamina (leaf blade) function

Answer 7

broadness provides large SA for maximum absorption of light

thinness provides short diffusion distance for gases, enables light to reach all mesophyll cells

Question 8

stomata function

Answer 8

opens in presence of light, allowing carbon dioxide to diffuse in and oxygen to diffuse out of the leaf

guard cells change shape causing the stomata to close and open. adjusts plants transpiration rates to external environmental conditions. (by regulating diffusion of water vapour)

Question 9

xylem and phloem function

Answer 9

xylem transports water and mineral salts to mesophyll cells, phloem transports sugars SUCROSE away from the leaf

Question 10

cambium

Answer 10

wall separating xylem and phloem

Question 11

what is transpiration

Answer 11

process which water vapour is lost from aerial parts of the plant as a result of evaporation of water

• from surface of (spongy) mesophyll cells via the air space in the leaf to the atmosphere
• then diffusion of water vapour out of the leaf thru stomata, down a water vapour conc grad

(mesophyll cells have thin water film arnd the outside the of cell)

Question 12

root pressure

Answer 12

active transport of ions into root xylem vessel lowers its water potential resulting in accumulation of water in the roots by osmosis and flows upwards a few metres but insufficient to reach tall tree leaves.

Question 13

transpiration stream

Answer 13

• as water leaves xylem vessels in leaf, a tension is set up on the entire water column in the xylem tissue
• as water has extremely strong adhesive and cohesive properties, results in flow of water up plant
• no energy expenditure

Question 14

humidity affecting transpiration

Answer 14

low humidity increases water vapour conc grad between leaf and atmosphere, increasing water evaporation

Question 15

temp affecting transpiration

Answer 15

a rise in surrounding temp will increase heat energy which in turn increases the evaporation of water from the surface of the mesophyll cells

Question 16

wind affecting transpiration

Answer 16

the stronger the wind, the higher the rate of transpiration as wind blows away saturated air from around the leaves, maintaining a conc grad between the leaf interior and air outside stomata.

Question 17

light intensity affecting transpiration

Answer 17

in sunlight during photosynthesis, the stomata will open and become wider due to gaseous exchange, allowing more water vapour to diffuse into the atmosphere

Question 18

water supply affecting trnaspiration

Answer 18

ample water supply will keep leaf cells turgid. Stomata remains open.

Question 19

when does wilting occur

Answer 19

under strong sunlight, when rate of transpiration exceeds rate of absorption of water by roots

Question 20

what happens when plants wilt

Answer 20

-cells lose turgor, become flaccid

• reduction of exposure of leaf surface to sunlight
• closure of stomata from excessive water loss, guard cells become flaccid
• decrease in rate of photosynthesis due to decrease in uptake of carbon dioxide, water and exposure of leaf area to sunlight

Question 21

transpiration is a consequence of gaseous exchange

Answer 21

Stomata must be open for gaseous exchange
as CO2 is needed for the light-indp stage of photosynthesis
while O2 is the by-product of light-depd photosynthesis
water vapour diffuse out thru open stomata during TRANSPIRATION

Question 22

properties of pholem

Answer 22

Sieve tubes, companion cells.

• sieve tubes are long, narrow, elongated elements connected end-to-end with reduced cytoplasm and absence of nucleus and many other organelles to maximise space for translocation of products of photosynthesis from leaves to other parts of the plant.
• sieve tubes are living tissues maintained by companion cells.

Question 23

why does rate of photosynthesis not increase even when I continue increasing the limiting factor?

Answer 23

As this point, light is no longer the limiting factor of photosynthesis.
CO2 concentration could be the limiting factor OF PHOTOSYNTHESIS instead.

Question 24

Stages of light-depd and indp photosynthesis

6 steps

Answer 24

1. photolysis of water molecules to hydrogen and oxygen. oxygen released as by-product.
2. hydrogen accepted by NADP: it is reduced to NADPH
3. CO2 diffused in stroma through stomata is fixed with ribulose biSphosphate in the presence of RuBisCo enzyme
4. Energy from adenosine triphosphate and hydrogen from NADPH is used to reduce 2 molecules of glycerate 3-phosphate to triose phosphate.
5. NADPH and adenosine triphosphate regenerate ribulose bisphosphate from triose phosphate so more CO2 can be fixed
6. NADPH and adenosine triphosphate activate triose phosphate for synthesis of complex organic compounds like carbohydrates (sucrose, starch), lipids and amino acids.

Question 25

photosynthesis eqn

Answer 25

carbon dioxide+water+light energy–>oxygen+glucose

Question 26

light dependent eqn (not impt)

Answer 26

H2O–> NADPH+ATP+O2

Question 27

light indp eqn (not impt)

Answer 27

NADPH+ ATP+CO2–>NADP+ADP+Pi+C6H12O6

Question 28

WHERE DES LIGHT INDP TAKE PLAce

Answer 28

stroma

Question 29

where does light depd take place

Answer 29

thylakoid membrane of the grana