A group of researchers wanted to determine how leaf herbivory and seed production of a legume plant (legumes are a family of plants which includes beans and lentils) were affected by the presence of...

A group of researchers wanted to determine how leaf herbivory and seed production of a legume plant (legumes are a family of plants which includes beans and lentils) were affected by the presence of its mutualistic rhizobia (a group of nitrogen-fixing bacteria). They designed an experiment with two treatments: (1) rhizobia absent and herbivores present and (2) rhizobia present and herbivores present. Provide two additional treatments and briefly explain how they would contribute to our understanding of the results of this experiment.