Allelopathy Journal

The effects of GA₃ and phyllocladane diterpenoids (calliterpenone and calliterpenone monoacetate) isolated from the Callicarpa macrophylla Vahl. were evaluated on the plant growth of Artemisia annua L., Hibiscus sabdariffa L. and Sesbania cannabina (Retz.) Pers. All these compounds inhibited the germination of H. sabdariffa (33–58%) and S. cannabina (30–46%), but enhanced the shoot growth of H. sabdariffa seedlings (14.1–21%) and S. cannabina (4–19%). These compounds inhibited the root growth of seedlings of test plants. Calliterpinone monoacetate at 0.1mM concentration caused 8–40% inhibition in H. sabdarifa and 27% in S. cannabina. Calliterpenone and calliterpenone monoacetate also reduced the inhibitory effects of seed leachates of A.annua. Mixing of 0.01 mM solution of calliterpenone and calliterpenone monoacetate with A. annua aqueous seed extract, slightly improved the seed germination but also considerably enhanced the shoot growth (76–87%) and root growth (35–60%) over control