Abstract: We investigated the signal relationship between phospholipase Dα1 (PLDα1) and the gas signal molecule hydrogen sulfide (H₂S) in Arabidopsis thaliana response to the allelopathy of diterpenoid oridonin. The wild type Arabidopsis Columbia (WT), phospholipase Dα1 (PLDα1) deletion mutant pldα1, D-/L-cysteine desulfyrase synthetic deletion mutant d-cdes and l-cdes seedlings were used as experiment materials, while 60 μmol·L^-1 oridonin was applied as treatment concentration. The results showed that oridonin significantly increased H₂S content, PLD and D-/L-CDes activities, and gene expressions of PLDα1 and D-/L-CDes in WT. Under oridonin treatment, the D-CDes and L-CDes activities of pldɑ1 seedlings were significantly lower than those of WT. Both D-CDes and L-CDes activities increased after exogenous addition of phosphatidic acid (PA) and were higher than those of WT. Oridonin significantly inhibited root growth of four lines, with d-cdes and l-cdes being more sensitive to oridonin. Application of NaHS promoted root growth and endogenous H₂S production of four lines under oridonin treatment, while application of PA increased root growth and endogenous H₂S production in WT, pldɑ1 and l-cdes, but had no effect in d-cdes. These results indicated that PLDα1 and H₂S played a vital role in driving the response of Arabidopsis to oridonin, and that PLDα1/PA was located at the upstream of D-CDes to participate the regulation of the H₂S production and root growth.