In what way could Beatrice's actions (causing Ruth to have a convulsion) be considered similar to gamma rays as a source of toxic energy?
There is no doubt that the first act of The Effect of Gamma Rays on Man-in-the-Moon Marigolds depicts a scene which is allegorical to the project in which Tillie is working about the effects of radiation on marigold's seeds: the project is allegorical to the effects of Beatrice's negative energy on the developmental processes of her two daughters, Tillie and Ruth.
There are different moments in the play that show the way in which Beatrice's life, devoid of purpose or dignity, brushes up on her young, and smart daughters. Ruth is obviously the most affected of the two daughters, because, aside from being the elder sister, she she also suffers from a pre-existing proneness to seizures that becomes more aggravated by her mother's mood swings and fits.
Tillie, aware of her surroundings but determined to move on, escapes her mother's toxic presence by devoting herself to her science project, and to the care of her pet rabbit. We see, however, that the sisters are not as bound and loyal as we would expect abused siblings to be. Ruth does not necessarily protect Tillie, nor does she go overboard to try to protect herself from her mother entirely. This leads the audience to wonder exactly to what extent has Beatrice's poisonous nature affected Ruth's sense of self.
Therefore, if the audience analyzes the results of Tillie's project, it will be able to correlate the dynamics taking place in Tillie's home with the processes taking place within the marigolds.
The result of the project goes as follows: the marigolds that were exposed to normal levels of Gamma radiation, meaning, lower exposure, bloomed with no secondary effects, nor weaknesses that could have been noted. However, those marigolds exposed to a higher, moderate level of radiation suffered strange mutations that did not amount to danger, but certainly defaced the expected appearance of the flower. However, the seeds that are exposed the most to the Gamma Rays, simply died; they were not strong enough to continue growing--they became stagnant, and then went nowhere.
Similarly, Ruth and Tilly represent the flowers affected by the toxic wrath of their mother. It is Ruth who has been subjected to most of her mother's behavior;she has completely become null and will be negatively affected by her mother, forever.
On the other hand, Tillie is the flower whose effects from the gamma rays does not denote any major changes. This is because Tillie defends herself from mother's shallow and empty attempts to bring her down by using the temperance of her character, and not by imitating her mother's empty and vain ways. However, it is hard to predict whether the toxic nature of Beatrice will linger forever in Tillie as it has already done with Ruth.