Proposal about the physiological response of invasive plants to air pollution

write the Literature Review/Background of the proposal
This section is used to further demonstrate the importance of your proposed work, provide details on what is already known about your subject, and to tie past research/literature to the objectives you are proposing. This differs from the traditional background section of a research paper in which you completely address all aspects of all topics regarding your research. This is an expanded version of your Problem statement. It may also include a discussion of preliminary data, a justification for your approach or novel methods, etc. However, portions of this information/lit review may be a better fit under the discussion of your specific approach to each of your objectives/aims in your Research Plan/Experimental Design.

there are three objectives, please all information that related to all subjects and the studies that have been done in the same topic.

Objectives:
-Identify the structural or physiological mechanisms that invasive plants used to adapt to air pollution.
-Determine the Air Pollution Tolerance Index (APTI) for tree of heaven (ailanthus altissima), common mulberry (morus alba), and Empress tree (Paulownia tomentosa).
-Compare between invasive and native plants response to air pollution.