The by-product of photosynthesis is oxygen, which is added to our atmosphere. plants also respire; creating atp, the energy they need to continue to grow, develop and reproduce. imagine it is summer; there is a drought. how will the summer drought influence the model we see here? a) in a response to the drought, stomata will open more frequently. there will be higher outputs of co2 and o2 as a result. b) an increase in temperature will cause an increase in chemical activity. there will be increases in all chemical inputs and outputs in the model. c) water will be a limiting reactant in the model. as a result, less glucose will be produced. there will be less co2 in and o2 and h2o out. d) water will be a limiting reactant in the model. there will be less h2o in through the roots and less h2o out via transpiration. the other inputs and outputs will remain constant.