Early experimentation on the single-celled organism Acetabularia led to important discoveries about the role of the nucleus in regulating cell function. Acetabularia is an enormous single cell with three distinct regions: a cap, a root-like rhizoid, and a stalk which connects the two. The following experiments were conducted to study the development of the cell:
Experiment 1
The stalk of an Acetabularia was cut, fragmenting the cell. The fragment which included the cap died shortly afterwards while the fragment containing the rhizoid regenerated to form a complete Acetabularia.
Experiment 2
The nucleus from Acetabularia mediterranea, which has a flat cap, was transplanted into Acetabularia crenulata, which has a tufted cap, following removal of the Acetabularia crenulata nucleus. The Acetabularia crenulata cap eventually assumed the flat shape.
Experiment 3
The nucleus of Acetabularia mediterranea was removed from the young cell before it first formed a cap. A normal cap formed several weeks later. The cell proved to be inviable and died shortly thereafter.
Experiment 4
A young Acetabularia was fractioned into a number of portions before it first formed a cap. Several weeks later, both the portion containing the nucleus and the portion containing the apical tip of the stalk formed caps. The other portions did not form caps.
Which of the following conclusions can be logically drawn from the fact that the Acetabularia segment containing the rhizoid regenerated a complete and viable Acetabularia in Experiment 1?