Monday, 3 February 2014


1) By looking at a plant externally can you tell whether a plant is C3or C4 why & how?

                                    Externally morphological characters’ generally do not judge C3 and C4 plants. But some common habitats and characters’ can judge mum. C4 leaves are generally isobilateral but all isobilateral leaves are not C4 in natural & leaves of C3 plants are generally dorsiventral.

            Habitat: -        C4 plants are tropical plants while C3 plants are found in all zones on earth.

2)         By looking at which internal structure of a plant can you tell whether a plant is C3 or C4 expert?

            In case of C4 plants :-             In C4 plants a leaf has kranz anatomy where the undifferentiated mesophyll occurs in concentrate layers around vascular bundles & each vascular bundle is surrounded by a bundle sheath of large sixed green cells. Starch grains do not occur in them.

            In case of C3 plants: - Bundle sheath is not large, nor they contain chloroplasts. Mesophyll is often differentiated into palisade & spongy parenchyma. They possess starch grass.

3)         Even though a very few cells in a C4 plant carry out byways the tic calves’ pathway yet they are highly productive. Can you discuss why?

            Calvin cycle is case of C4 plants occurs is bundle sheath. C4 plants have a high rate of photosynthesis due to

1)         Rapid supply of CO2 from all mesophyll cells taking part in initial carbon dioxide fixation.

ii)         Absence of photorespiration due to absence of photolysis in bundle sheath cells.

iii)        Rapid windrow of photosysthates from the bundle sheath cells as they lie occur the vascular bundles.

4)         Rubisco is an enzyme that acts both as a carboxylase and oxygenize. Why do you think Rubio co carries out more carboxylation in C4 plants?

            Rubisco functions as oxygenize only when there is higher cone of oxygen & lower cone of CO2. Both the conditions do not occurs in Rubisco containing bundle sheath cells of C4 plants. They do not have photolytic evolution of oxygen they receive a regular supply of CO2 even when the stomata are closed.

             Rlubisco of C4 plants functions only as carboxyl is.

5.         Suppose there were plants that had a high concentration of chlorophyll a would it carry out photosynthesis? Then why do plants have chlorophylls to and other accessory pigments?

            Chlorophyll a is essential for photosynthesis because only its special molecules function as reaction centers (P700, P688) Reaction centers convert light energy into chemical of electron energy. Photosynthesis is absent is plants lacking chlorophyll a. /

            The importance of chlorophyll b & other accessory pigment is (i) Absorption of light rays of different wavelengths & transfer of this energy to reaction centre through resonance.

            ii) Protection of chlorophyll a reaction centre from nascent oxygen & the other destructive radicals.

6)         Why is the color of leaf kept is the dark frequently yellow or pale green? Which pigment do you think is more stable?

            It will become yellow or pale green when kept in dark because of the disintegration of chlorophylls careopnoids which provide yellow color to the leaf are more stable.

7)         look at leaves of the same plant on the shady side & compare it with the leaves on the sunny side orcorupane the potted plants kept in the sun light with those in the shade. Which of them has leaves that are darker green? Why?

            Shaded leaves are dark green due to the reason

            i) Photo oxidation of chlorophyll is bright light & its non oxidation is shaded region.

ii)         Orientation of chloroplasts in vertical files along the walls in strong light & their irregular arrangement in shade.

8.         Figures show the effect of light on the rate of photosynthesis Basic on the graph, answer the following question

            a) A which points (A, B or C) in the curve are a light limiting factor.

            b) What could be the limiting factor/s in the region A.

            c) What do C and D represent on the curve?


                        a) light is limiting in A & 50% of B.

                        b) light

                        C-factors other than light (like Co2) is limiting
                         D- light oration point under existing conditions of other factors.

9)         Give comparison between the following:

                        a) C3 & C4 pathways
                        b) Cyclic & non-cyclic ph to phosphor reach
                        c) Anatomy of leaf in C3 & C4 plants.

a) C3 Pathways

i) Optimum temperature for photosynthesis is 10-250 C

2) Serrations point is reached at 10-700 of full sunlight

3) Photosynthesis stops under conditions of water stress

4) Phospoglyciric acid is 1st product
C4 Pathways

1) Optimum temperature is 300-450 C

2) Serration point is not reached even at full sunlight

3) It is not stopped.

4) Oxalo – acetic acid is the first product.

Cyclic photo phosporyleation

1) It is performed by photo system Independently.

ii) An external source of electron is not required

iii) Synthesis only ATP

i) It is performed by collaboration of both photo system I & II

ii) The process requires an external electron donor

iii) Synthesis ATP & produce NADPIT 

C) Anatomy of leaf in C3 & C4 plants

C3  Plants

a) The leaves do not possess Kranz & anatomy

b) Chlorophyll do not have peripheral reticulum

c) Chloroplast are of one type

d) Bundle neat cells usually do not contain chloroplasts
C4 plants

a) They have

b) They have

c) They are two types

They possess prominent chloroplasts.

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