Theory:

Onion root-meristematic tissue experiment:
Onion bulb experiment - presence of apical meristem
  • Take two jars (jar \(1\) & jar \(2\)) and two onion bulbs with roots protruding from them. Pour water into the jars until the jars are nearly full.
  • Place the two onions with their roots immersed in the water into each of the jars as shown in the picture.
  • Measure the length of the roots on day \(1\), \(2\) and \(3\).
  • After a few days we observe that both the roots have grown to a certain length.
  • Take onion bulb out of the jar \(2\) and cut the tip of the root by about \(1\) cm. Place it again in the jar and observe the growth of roots in both jar \(1\) and jar \(2\) for another \(5\) days. Mark the jar of the root-trimmed onion bulb.
Note the measurement of the length of the roots in the below table before cutting the tip of the root:
  
 
Day \(1\)
Day \(2\)
Day \(3\)
Jar \(1\)
 
 
 
Jar \(2\)
 
 
 
  
Note the measurement of the length of the roots in the below table after cutting the tip of the root:
  
 
Day \(1\)
Day \(2\)
Day \(3\)
Day \(4\)
Day \(5\)
Jar\(1\)
 
 
 
 
 
Jar \(2\)
 
 
 
 
 
Questions:
  1. Is there a difference in length of roots between the root-trimmed onion (in jar \(2\)) and the un-trimmed one (in jar \(1\))? Give reasons.
  2. Do the roots continue growing even after we have removed their tip?
Answers:
  1. Yes, there will be a difference in the length of the roots. The root-trimmed onion's root (in jar \(2\)) is shorter in length than the un-trimmed one (in jar \(1\)). Tips of the plant roots contain apical meristematic tissue, and is responsible for the elongation or length of the roots. As the tip of the onion roots in jar \(2\) is cut, apical meristematic tissue is removed from it. There will not be any observable growth in the roots of the onion in jar \(2\) . So the length of the roots of the onion in jar \(2\) is lesser than the length of the roots of the onion in jar\(1\).
  2. No, the roots won't  grow after their tips are removed. Tips of the plant roots contain apical meristematic tissue, and is responsible for the elongation or length of the roots. As the tip of the onion roots in jar \(2\) is cut, apical meristematic tissue is removed from it. So there will not be any growth in the roots of the onion in jar \(2\) after the tips are cut.