To cite photosynthesis in publications use:

Stinziano JR, Roback C, Gamble D, Murphy B, Hudson P, Muir CD (2020). “photosynthesis: tools for plant ecophysiology & modeling.” R package version 2.0.1, https://CRAN.R-project.org/package=photosynthesis.

Corresponding BibTeX entry:

  @Misc{,
    title = {photosynthesis: tools for plant ecophysiology & modeling},
    author = {Joseph R Stinziano and Cassaundra Roback and Demi Gamble
      and Bridget Murphy and Patrick Hudson and Christopher D Muir},
    note = {R package version 2.0.1},
    year = {2020},
    url = {https://CRAN.R-project.org/package=photosynthesis},
  }