You are touring a local greenhouse with two rooms and you notice that many of the plants in one of the rooms of the greenhouse are not as large when compared to the same plants being grown in other parts of the greenhouse. You speak with the manager who says she has been having a problem recently with growing plants in this one room. Later in the conversation you learn that the manager has looked at factors such as light levels, temperature and soil nutrients, yet all these are the same in both rooms. What factors would you suggest testing for, and how would each of these factors affect the growth of plants?