Experiments on Acetabularia by Hammerling:
Hammerling conducted experiments on the single-celled green alga Acetabularia, which has a large, visible nucleus. These experiments helped to determine the role of the nucleus in heredity.
Key Findings:
1. Regeneration of Acetabularia: Hammerling observed that when the cap of an Acetabularia cell is removed, it can regenerate a new cap. This regeneration occurs even when the nucleus is removed from the original cell and replaced with a nucleus from a different species of Acetabularia.
2. Nucleus Determines Cap Formation: The regenerated cap of Acetabularia always resembled the species of the nucleus used, rather than the species of the cytoplasm. This indicated that the nucleus has a significant role in determining the developmental characteristics of the cap.
3. Role of Cytoplasm: Hammerling also observed that the cytoplasm of the Acetabularia cell did not influence the developmental characteristics of the cap. Even when the cytoplasm was replaced with cytoplasm from a different species, the regenerated cap still resembled the species of the nucleus.
4. Importance of Nucleoplasmic Ratio: Hammerling further investigated the role of the nucleus by conducting experiments where he manipulated the nucleoplasmic ratio. He found that when the nucleus was transplanted into a smaller cytoplasmic volume, the regenerated cap was smaller, and vice versa. This indicated that the nucleoplasmic ratio plays a role in determining the size of the cap.
Conclusion:
Hammerling's experiments on Acetabularia provided evidence for the role of the nucleus in heredity and developmental characteristics. The nucleus was found to determine the cap formation, while the cytoplasm had little influence. The experiments also highlighted the importance of the nucleoplasmic ratio in determining the size of the cap. These findings contributed to our understanding of the role of the nucleus and its genetic material in controlling cellular development and heredity.