Biological Classification Question 10
10. One scientist cultured Cladophora in a suspension of Azotobacter and illuminated the culture by splitting light through a prism. He observed that bacteria accumulated mainly in the region of :
(a) Blue and red ligh
(b) Violet and green light
(c) Indigo and green light
(d) Orange and yellow light
Show Answer
Answer : a
Hints & Solutions
(a) Azotobacter is aerobic bacteria and Cladophora is green alga. Engelmann used a prism to split light into its spectral components, and then illuminated a green alga, Cladophora, placed in a suspension of aerobic bacteria. The bacteria were used to detect the sites of oxygen evolution. He observed that aerobic bacteria accumulated mainly in the region of blue and red light of the split spectrum thus giving the first action spectrum of photosynthesis. Theodor Wilhelm Engelmann was a German botanist, whose 1882 experiment measured the effects of different colours of light on photosynthetic activity and showed that the conversion of light energy to chemical energy took place in the chloroplast.
