Breaking seed dormancy and determining cardinal temperatures for Malva sylvestris using nonlinear regression

This experiment was conducted to break dormancy of tall mallow (Malva sylvestris) seeds and estimate cardinal temperatures using non-linear regression. Scarification of seeds by concentrated sulphuric acid is the most effective method for breaking dormancy of tall mallow seeds. However, response to sulphuric acid treatment varied with seed storage. Treating freshly harvested seeds with sulphuric acid for 240 and 270 minutes resulted in the highest germination, while six months later, the highest germination was achieved with 120 minutes treatment. Different results were also obtained from scarification of fresh seeds and stored seeds by sandpaper. After finding out the best treatment for breaking dormancy, the seeds were placed under a range of temperatures between 5 and 40°C, and non-linear regression models used to determine cardinal temperatures. A dent-like model provided the best fit to the data and was used to estimate cardinal temperatures. Base, optimum and maximum temperatures were estimated as approximately 1, 23 to 34, and 42°C, respectively with this model. This is the first report on cardinal temperatures of tall mallow.