Question

Choose the correct answer from the alternatives given.
In an experiment, oat (Avena sativa) seedlings were grown under the same conditions of temperature, moisture and light. Their tips were removed and divided into four groups. Each group was given different treatments and the growth was measured carefully after keeping them in dark for 16 Firs. Which of the following groups had the most growth?

• A. In Group I, the tip was put back on each seedling
• B. In Group II, a block of agar gel containing juice of 10 tips was placed on top of each seedling
• C. In Group III, nothing was placed on top of each seedling
• D. In Group IV, a drop of water was placed on top of each seedling

Answer 1

The correct option is B In Group II, a block of agar gel containing juice of 10 tips was placed on top of each seedling

When the tip of the seedlings was covered with agar gel and is placed on seedling, The hormones which were later found to be auxins move from base to the apex. Thus the growth of the seedling was in the direction of more concentration of agar. As they were kept in dark, there was no light for growth so the seedlings have taken agar gel as the source of growth. While in those seedlings whose tips were again placed back on seedling or drop of water was placed on top of each seedling, growth does not occur as there is no medium for growth.

So, the correct option is 'In Group II, a block of agar gel containing juice of 10 tips was placed on top of each seedling'.