Apparatus : Few pea seeds, raw sand, marking pencil, blotting paper, petridish, scale, etc.
1. A few pea seeds are taken and placed on moist sand for 24-28 hours. The radicles are seen to come out of the seeds after some time.
2. The seedling with a radicle measuring more than 3cm in leghth is chosen.
3. The radicle is divided and marked into 15 equal parts from the tip to top.
4. The seedling is placed on a moist blotting paper and kept in a petridish undisturbed for 3-4 days.
The figure shows.
A. Youngroot marked into 1 mm zones.
B. The same after 24 hours.
Observation : After 3-4 days it is observed that the size of the radicle increases. The distance between the marks near the tip remains almost the same. But in the middle, distance between the marks increased and at the upper end again the distance remained the same.
Result : The distance between marks in upper and lower regions remains the same. Thus, no growth has taken place. But the middle part where the growth has taken place is called phase of elongation.
Auxin was isolated by F.W. Went from tips of coleoptiles of oat seedling.
Auxins are of two types :
(1) Natural auxins : These are naturally occuring auxins, isolated from plants and are regarded as phytohormones e.g. IAA. NAA etc.
(2) Synthetic auxins : These are synthesized by artificially e.g. IBA 2,4-D etc.