Stimulation of root growth and enhanced nitrogenous metabolite content in habanero pepper (Capsicum chinense Jacq.) treated with a d-amino acid mixture

d-amino acids (d-AAs) can be found in soils, and recent studies indicate that plants exhibit multiple behaviors in response to the type of d-AAs present. d-Ala and d-Ser have the greatest adverse effects on plant growth and development, however the role of d-Ala as a source of nitrogen (N) and d-Ser as an agonist of glutamate receptors (GLRs) in plants have been proposed. Though, there is very little knowledge about the role of d-AAs in regulating plant growth. In this paper we report the effect of d-AAs on the root growth of habanero pepper (Capsicum chinense Jacq.). It was found that the primary root (PR) was more sensitive to d-Asp and d-Ala, which caused a complete halt in the growth of the organ. The lateral root (LR) number increased following the application of d-Leu either individually or in a mixture with d-Val and d-Cys. Also, d-Val increased the leaf area. Overall, the three d-AAs acted synergistically to increase the total radical length. The mixture of these three d-AAs increased the concentration of nitrate, total amino acids, and protein. These results suggest that d-Val, d-Leu, and d-Cys regulate cellular metabolism and stimulate root growth. Here we provide important information to understand the role of d-AAs in the regulation of root plant growth.