Hammerling's Acetabularia grafting experiment

Hammerling's Acetabularia grafting experiment that established nucleus as the store house of hereditary material.

Hammering's grafting experiment using Acetabularia cleared all speculations and confirmed the role of nucleus in heredity. His experimental material Acetabularia is a large single celled, uni-nucleate alga.

The algal body is ~6cm long and consists of a foot, a stalk and a cap (largest unicelled organism). The upper cap or crown has a characteristic shape for each species. Cap has the regeneration potential if damaged or removed. The single nucleus is seen in the rhizoid region. 

He took two species for the experiment, A.mediterranea with a characteristic cap of 81 rays and rounded tips and A. crenulata with a cap of 31 rays and pointed tips. The algae are capable of regeneration from any part. So that cap, stalk or even nucleated rhizoid portion is removed, it will soon regenerate and give rise to a whole plant. But the enucleated portion on continuous decapitations (or removal) loses the regeneration capacity whereas the nucleated region always retains the regeneration capacity.

Hammerling's Acetabularia grafting experiment

He grafted the stalk of A.crenulata with the rhizhoid region (having nucleus) of  A.mediterranea and vice versa.

Then he grafted the rhizoid region of both the species (2 nuclei from both species in a common cytoplasm). Upon regeneration, all were of an intermediate type cap.

Further removed the stalk and allowed to regenerate. Upon regeneration the second cap formed was similar to that of cap of species that provides the nucleus.

An intermediate cap is the result from the rhizoid with nucleus of both the species. (two nucleus in a common cytoplasm).

The result clearly proved beyond doubt that nucleus is the site of hereditary material and not the cytoplasm.

Summary of the experiment

Experiment:1

A.crenulata (stalk) + A.mediterranea (rhizoid with nucleus)->regenerated to intermediate type cap->stalk removed-------à regenerated from rhizoids into A.mediterranea type cap (rhizoid with nucleus or nuclear donor).
Experiement:2

A.crenulata (rhizoid with nucleus) + A.mediterranea (rhizoid with nucleus)->regenerated to intermediate type cap->stalk removed-------à regenerated from rhizoids into intermediate type cap (rhizoid with 2 nuclei from both species, character of both the species as both nuclei are present in a common cytoplasm)

Experiment:3

A.crenulata (rhizoid with nucleus) + A.mediterranea (stalk without nucleus)--->regenerated to intermediate type cap->stalk removed-------à regenerated from rhizoids into A.crenulata type cap (rhizoid with nucleus or nuclear donor).

Conclusion:

The type of the cap is determined by the nucleus present in the rhizoids. 

If both the nuclei (from 2 species) are present in the same cytoplasm, an intermediate type of cap develops.