Question

Observe the diagram and read the following to answer: (1x4 = 4m)

The C4 plants often possess a characteristic leaf anatomy called kranz anatomy, from the German word for wreath. Their vascular bundles are surrounded by two rings of cells; the inner ring, called bundle sheath cells and the outer ring, called mesophyll cells. The chloroplasts in this anatomy are called dimorphic. 
C4 plants have a competitive advantage over plants possessing the more common C3 carbon fixation pathway under conditions of drought, high temperatures, and nitrogen or CO2 limitation. When grown in the same environment, at 30 °C, C3 grasses lose approximately 833 molecules of water per CO2 molecule that is fixed, whereas C4 grasses lose only 277. Today, C4 plants represent about 5% of Earth's plant biomass and 3% of its known plant species. Despite this scarcity, they account for about 23% of terrestrial carbon fixation. Increasing the proportion of C4 plants on earth could assist biosequestration of CO2 and represent an important climate change avoidance strategy. Present-day C4 plants are concentrated in the tropics and subtropics where the high air temperature increases rates of photorespiration in C3 plants.

(i) What does 3 and 4 signify in C3 and C4 plants?
(a) 3-phosphoglyceric acid and oxalopropanoic acid
(b) 2-phosphoglyceric acid and oxaloacetic acid
(c) 3-phosphoglyceric acid and oxaloacetic acid
(d) 1-phosphoglyceric acid and oxalopentanoic acid

(ii) What do you mean by “dimorphic chloroplasts”?
(a) Different sizes of chloroplasts in C4 plants
(b) Different sizes of chloroplasts in C3 plants
(c) Different sizes of chloroplasts in C3 and C4 plants
(d) Different size and number of chloroplasts in Kranz anatomy

(iii) Biosequestration is solution to global climate change problem. C4 plants help in biosequestration because-
(a) they have effective CO2 concentration mechanism in bundle sheath cells
(b) they have effective CO2 concentration mechanism in mesophyll cells
(c) they have Kranz anatomy
(d) Both (a) and (c)

(iv) Identify plants that do not show photorespiration from these:
(a) Rice, wheat (b) Maize. sorghum (c) Maize, rice (d) All show photorespiration
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Answer 1

Answer:

1) 3-phosphoglyceric acid and oxaloacetic acid

2) Different sizes of chloroplasts in C4 plants

4) Maize. sorghum

Answer 2

Explanation:

3-phosphoglyceric acid and oxaloacetic acid