Went's experiment- Stem curvature test

Theory

Increment of the stem occurs due to the concentration of the Auxin produced at the apical region.

Therefore;

1.      Increment of the length ∝ Concentration of Auxin      1

As the tips of the shoots are placed on the Agar surface where the Auxin is available,

2.      Number of tips ∝ Concentration of Auxin

From equation 1 and 2;

Increment of the length ∝ Number of tips

This is used to plot the graph.

Procedure

The apices of the provided Vigna sinensis plant stems were cut off using a razor blade.

Each of them was placed erect on the agar surface which allows equal distribution of Auxin among them in the Petri dish.

-Tips placed on the Agar surface in the petri dish-

 Groups should be formed and each of it should place 10, 20, 30, 40, 50 or 60 tips on theirs Petri dishes.

Dishes were incubated for 20 hours.

Tips were removed from the Petri dishes and dishes were transferred into the refrigerator.

After two days the apices of the provided Vigna sinensis plants grown in pots were removed with a blade.

Initial height of the decapitated stems was measured.

Small cubes about 2×2 mm² of agar from the dishes where the tips had been placed were taken off.

They were placed symmetrically on the decapitated stems.

A control was also setup with an untreated agar block of the same size.

Plants were observed again after 72hours and measured the height of the plants.

What is the effect of replacing the shoot tip with treated agar?

It would provide homogenous concentration of Auxin to all the test plants. Also it would be easy to carry out with control plant, without treating the agar with Auxin.

What were the practical difficulties you faced in this experiment?

Apices of the provided plants are very small. Therefore it had to be removed very carefully.

Diameter of the plant is also very small. Therefore placing the agar block on the decapitated plant was difficult.