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Aims: The aim of the study was to determine whether and to what extent any of a family of amphiphilic heptapeptide synthetic anion transporters (SATs) affected the growth or root morphology of Arabidopsis thaliana. Study Design:  A. thaliana plants were grown from seedlings in PNS media in the absence or presence of one of 21 SATs. Place and Duration of Study: Departments of Chemistry & Biochemistry, University of Missouri – St. Louis, 1 University Blvd., St. Louis, MO 63121 U. S. A. The study was conducted 2017-2018. Methodology: Twenty one compounds of the form R2N-COCH2YCH2CO-(Aaa)3Pro(Aaa)3-O(CH2)6CH3 were prepared and studied. The amino acids included Ala, Gly, and Ser. R was normal alkyl having 6, 10, 12, or 18 carbons. Y was methylene, oxygen, sulfur, or absent. The PNS media was infused with various concentrations of the SAT and 21 plants in each group were allowed to grow for 11 days. Overall plant growth and root morphology were visualized and/or measured and the results recorded. Results: A comparison of primary root length and lateral root number revealed that the greatest alterations in lateral root densities were observed for peptide sequences of the type GGGPSGS, whether or not serine was protected by t-butyl. Differences were also observed for these peptide sequences according to the identity of Y in the ~COCH2YCH2CO~ chain. Conclusion: The presence of serine’s oxygen atoms on the C-terminal side of the heptapeptide interact with Cl¯ leading to a change in ion concentrations and alterations in primary root lengths and lateral root densities.