Germination biology and phenological development stages of false jagged-chickweed (Lepyrodiclis holosteoides).
False jagged-chickweed (Lepyrodiclis holosteoides (C.A. Mey.) Fenzl ex Fisch. & C.A. Mey.) is an invasive weed species distributed in many regions of Iran. Scientific knowledge about the biology and ecology of false jagged-chickweed is rare. In a series of laboratory experiments, the effect of chilling treatments, potassium nitrate (KNO3), gibberellic acid (GA3), concentrations, temperature regimes, and sowing depths on seed germination and breaking seed dormancy of false jagged-chickweed was studied. In two field experiments the phenology of false jagged-chickweed and winter wheat (Triticum aestivum) was also compared. Chilling treatment for 15 days, a KNO3 concentration of 30 µmolar and a GA3 concentration of 144 µmolar increased germination percentage and germination rate. However, chilling treatment for 15 days did not increase germination rate as well as the KNO3 and GA3 treatments. A quadratic polynomial model predicted that the optimum temperature giving the maximum germination percentage was 22°C. Seedlings emerged in a range of sowing depths from 0 to 8 cm, while no seedling emergence occurred at sowing depths greater than 10 cm. Based on a Gaussian model, the optimum sowing depth was predicted to be 3.9 cm. False jagged-chickweed required higher GDD for seedling emergence than winter wheat, while the flowering stage of false jagged-chickweed occurred earlier than winter wheat. Results achieved in the present study are of interest not only for studying other life cycle aspects of this species but also as basic information for developing management strategies.