Question

A scientist has a house just beside a busy highway. He collects leaves from some plants growing in his garden to do radio-carbon ****** (to estimate the age of the plant by estimating the amount of a radioisotope of carbon in its tissues). Surprisingly the radio-carbon ****** shows that the plant is a few thousand years old. (a) Was the result of the radio-carbon ****** wrong or can you propose a reason for such an observation? (b) What simple experiment can be done to test the reason that you have proposed? Select the correct answer from above options

Answer 1

(a) The result of radio-carbon ****** was correct. Reason Vehicles running on the highway beside the house emitted carbon dioxide from the combustion of petrol or diesel, which are fossil fuels. The carbon in this carbon dioxide, coming from living material that has been converted into petroleum millions of years ago, would get assimilated into the tissues of the plant as it uses carbon dioxide from the surrounding atmosphere for photosynthesis. Therefore, tissues of the plant, when used for radio-carbon ******, would show the age of the plant to be many thousands of years old. (b) A simple experiment to test the validity of this explanation would be to collect seeds from the plants and grow them in a plot of land away from the highway or other sources of CO2 coming from the burning of fossil fuels. Radio-carbon ****** of plants growing from these seeds should show them as young plants.