Evaluate the collective function of references cited together in a given text segment.
Classify their combined role into one of the following categories: 'method', 'background', or 'result'.

Text:…plants exposed to increased content of non humified nutrients can be affected by many mechanisms, such as damages in chloroplast ultrastructure, carbon supply depletion and disturbances in photosynthesis, which may result in stunted root growth and leaf chlorosis (Bitts anszky et al., 2015).
Category: