Investigating the effects of temperature on seed germination of cutleaf geranium (Geranium dissectum L.) and determination of its cardinal temperatures

Abstract

Cutleaf geranium is a weed infesting crop fields in various parts of the world. The present study was conducted to determine the cardinal temperatures of germination for its seeds to have a better understanding about temperature needs of this species. Since the seeds were dormant after being harvested, they underwent different dormancy breaking methods. Then, cardinal temperatures were estimated. Among dormancy breaking methods including constant and alternating temperatures, gibberellic acid, H2SO4 and gibberellic acid+ H2SO4 treatments, pre-chilling and after-ripening, after-ripening was the most successful one. Dent and segmented models were the most suitable models for determination of cardinal temperatures. Base, optimum, and ceiling temperatures for dent model were estimated 0.02, 18.97 to 25.32, and 27.00 °C, respectively. These values for segmented model were 0.01, 24.3 and 27.08 °C. The seeds showed high germination uniformity at 15 and 20 °C, but they entered into a state of thermo-dormancy as temperature reached about 27 °C. According to the temperature conditions of the studied region, early sowing of canola will result in the weed being faced with higher than ceiling temperatures. Thus, generalizing, the proper sowing date may be regarded as a feasible management practice in controlling this weed in any given area. This was the first report on estimation of cardinal temperatures in cutleaf geranium.