Abstract: This research was conducted to test the instructional effectiveness that provides representative and argumentation tasks to stimulate reasoning, in order to promote system thinking on the topic of plant basic tissue systems. Testing is done through one group postest only design toward 30 pre-service biology teacher. Research data is in the form of reasoning complexity using multiple representations and thinking abilities that are collected through the analysis of completed worksheets and written tests. The results showed the use of multiple representations supported by arguments stimulating reasoning and correlating with the achievement of system thinking abilities. Learning that gradually involves direct observation activities, visualization and the use of models and modeling that uses discourse support for argumentation provides scaffolding in systems thinking.