09 Tys Unit 2 (pure)

4/1/09 

NUTRITION AND TRANSPORT IN PLANTS

Unit 2.2 Structured Q1 a) % increase in mass = (450-150)/150 X 100%

Unit 2.2

  Structure Qn 1, 2, 3

= 200% b)  Container A: The available CO2 in the water has been

used up during rapid photosynthesis.

Unit 2.3

  Structure Qn 1, 2, 3

  Essay Qn 2, 3

Structured Q1 c)  A; A contains the highest mass of water plants and they

will take up the most amount of oxygen as they respire throughout the day. d)  Green; Least photosynthetic activity takes place in

green light.

Container B: Since photosynthesis took place at a slower rate, CO2 was still present for photosynthesis to take place.

Structured Q2 a)  As light intensity increases, the rate of photosynthesis

increases. b)  D; at low light intensity, Plant D has a higher rate of

photosynthesis. c)  (i) Table 2 data shows at 80 lux, light intensity is no

longer the limiting factor. Rate of photosynthesis is limited by other factors like conc. of carbon dioxide, temperature. At high light intensity more energy is available to drive the reactions in the Dark stage. The energy is sufficient to convert a larger amount of CO2 into glucose.

Structured Q2 c)  (ii) Enzymes controlling the rate of Dark/light

independent stage is limited by temperature. Increasing temperature increases the rate of effective collisions between enzyme and substrate, resulting in higher rate of photosynthesis.

d)  When a plant wilts, its leaves droop and less surface

area is exposed to sunlight, resulting in less amount of sunlight available for photosynthesis; Stomata close to cut down loss of water via transpiration, also lowering the amount of CO2 entering leaves and resulting in less amount of CO2 available for photosynthesis; The plant wilting also indicates that the plant is absorbing insufficient water, which also indicates that there is less water available for photosynthesis.

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Structured Q3 a)  A: Guard cell; B: Upper epidermal cell; C: Phloem cell b)  i)

Air chambers help to keep leaf afloat on the water surface;

ii) It traps air containing CO2 necessary for photosynthesis.

Structured Q3 d)  Xylem in land plant will have thick, lignified wall.

Thick lignified wall provides mechanical support to the plant as it cannot rely on buoyancy to keep it upright.

c) 1. Stomata found on upper epidermis, none found on lower epidermis. 2. Air spaces found in palisade mesophyll layer. 3. Lower epidermal cells contain chloroplasts.

Unit 2.3 Structured Q1 a)  i)

Plant B

d)  Slight decrease in loss in mass.

ii) Loss in mass = 37.0 – 35.0 = 2.0g b)  i)

Transpiration

ii) Rate of Transpiration decreases. Water vapour lost by Plant A is kept within polythene bag which kept the surroundings of Plant A humid, thus lowering transpiration rate.

Structured Q2 a)  i)

Transpiration;

ii)  Leaf E droops but leaf G remains upright;

Depth of cut at Y is more than at Z – xylem tissue is removed in Y; Leaf E does no receive water and its cells lose turgidity, thus it wilts. c) 

Structured Q1

Cut at Z removed phloem tissue but not xylem tissue; leaf G continued to to receive water for photosynthesis; the bag enclosing leaf G allows G to reabsorb CO2 it produced from respiration; The CO2 and water allowed leaf G to photosynthesize and make glucose, which was converted to starch for storage.

Most stomata are found on the lower surface of leaves, and less stomata on the upper surface; Even if the upper surface is coated with vaseline most of the water still can be transpired through the numerous stomata on lower surface;

Structured Q3 (not in syllabus) a)  i)

1. Plant H is shorter and has thinner stem than plant G. 2. Leaves on plant H are small and yellow while leave on plant G are large and dark green. 3. Plant H has poorly developed roots, Or plant H has fewer leaves;

ii) Magnesium ion – is a constituent of chlorophyll; Lack of magnesium reflected by small and yellow leaves. Phosphate ion – needed for good root growth. Nitrogen ion – for growing of leaves; iii) Chlorophyll

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Structured Q3 b)  i)

Air in jar containing shoot K is more humid than air in jar containing shoot J.

ii) Shoot loses water vapour through leaves by transpiration; In jar containing shoot J, water vapour diffuses out of jar into dry air outside. In jar containing shoot K, water vapour remains in jar due to glass cover; The air becomes humid and lowers evaporation and diffusion rate of water loss from leaves, reducing transpiration rate in K.

Essay Q2 (pls make changes in marking scheme) a)  When leaf cells respire, they use oxygen and produce CO2

[1/2]

When they photosynthesize, they use CO2 and produce oxygen [1/2] When the rate of photosynthesis and the rate of respiration becomes equal, compensation point is reached; The O2 given out by photosynthesis is used in respiration and the CO2 given out in respiration is used in photosynthesis; Hence there is no diffusion gradient resulting in no net diffusion of gases between surrounding air and leaf air spaces;

Essay Q2

Essay Qn 2

b) Water from the xylem enters the leaf cells through osmosis; Water molecules then moves out of the spongy mesophyll cells to form a thin film over their surface; Water then evaporates from this film into the intercellular air spaces; As the concentration of water vapour is higher in the air spaces compared to the surrounding air outside, water vapour then diffuses out of the leaf through the stomata, DOWN the concentration gradient.

Essay Qn 2 c)  There are more stomata found on the lower epidermis

than the upper epidermis; As water is loss through the stomata, more water vapour diffuses out through the lower surface.

Essay Qn 3a i) 

Decreasing level of humidity results in the air having less water vapour, leading to a steeper water vapour diffusion gradient between the air spaces of the leaf and the outside of the leaf. As the gradient increases, more water vapour exits the leaf from the air spaces in the spongy mesophyll into the surrounding air through the stomata. As more water is lost through the stomata, the transpiration rate increases.

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Essay Qn 3a ii)  Increasing the temperature of surrounding air

decreases the humidity of the air outside the leaf.

It also increases the evaporation of water in the leaf as the water molecules gain more kinetic energy. These result in a steeper water vapour diffusion gradient between the air spaces of the spongy mesophyll and the outside of the leaf, resulting in more water loss through the stomata, increasing transpiration rate. If the temperature rise is too much, the loss of water from the guard cells will close the stomatal pore and reduce the rate of transpiration.

Essay Qn 3b 1.  Transpiration creates a pull to allows plants to conduct

water, including mineral salts dissolved in the water, from the roots to rest of the plant cells through the xylem. 2.  It also provides water required by cells to maintain

their turgor pressure which also provides support and structure of the plant. 3.  Transpiration allows the plant to lose latent heat of

evaporation which in turn keeps the plant cool when the surrounding temperature is high.

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