For example, the investigator would provide different levels of pollutant and observe plant responses to those various levels, again, working in the laboratory, greenhouse, or other controlled environmental situation.
(the investigator; would provide; different levels of pollutant) (the investigator; observe; plant responses; to those various levels; T:again)
the investigator the investigator
would provide observe
different levels of pollutant
plant responses to those various levels T:again