Thus we calculated, for every day d of every experimental session k, the parameters〖 L〗_k^((T) ) (d) , defined as the arithmetic mean of the length l_i (d) of the seedling belonging to the treated sample, and 〖 L〗_k^((C) ) (d) , defined as the arithmetic mean of the length l_i (d) of the seedling belonging to the control sample. Moreover, we defined 〖 σ〗_k^((T) ) (d) and 〖 σ〗_k^((C) ) (d) as the corresponding standard errors of the means.