Root competition among neighboring plants was studied by growing plants with their roots inside tubes of pvc pipes. some tubes had holes of varying sizes, allowing their neighbors' roots to enter the tubes of a target plant. as the percentage of a target plant's tube open to neighbors' roots increased,

Target plant biomass decreased and neighbor plant root biomass increased.

Explanation:

As the percentage of a target plant's tube open to neighbors' roots increased, target plant biomass decreased and neighbor plant root biomass increased. The study was designed to investigate the relationship  between neighbor root biomass and belowground competition. When the number of target plant's tube open to neighbors' roots increased, target plant biomass decreased and neighbor plant root biomass increased.