Preventing thermo-inhibition in carrot by seed priming

High temperatures during sowing may delay or inhibit carrot seed germination. Seed priming has been used in several species to improve and/or accelerate seed germination and to promote uniform seedling emergence in the field, especially under adverse conditions. The aim of this study was to evaluate the negative effects of high temperatures in carrot seed germination as well as to verify the benefits of priming treatment on carrot seed germination at high temperatures. Two experiments were carried out in this study. Firstly, 'Brasilia' carrot seeds were incubated at 35 degrees C for different periods of 24, 48, 72 and 96 hours and then, transferred to 20 degrees C. Seeds were also incubated at constant temperatures of 20 degrees C (optima) and 35 degrees C (adverse). In another experiment, seeds were primed in aerated solution of polyethylene glycol - PEG 6000 (30%), for 72 hours, at 15 degrees C, in light. Seeds were germinated at 20 and 35 degrees C and also sowed in substrate under greenhouse conditions. Constant high temperatures (35 degrees C) decreased the total germination. In addition, seeds that remained incubated at 35 degrees C for long periods had a lower germination when transferred to 20 degrees C. In normal conditions (20 degrees C), germination did not differ between primed and non-primed seeds, although seedling emergence rate was higher in primed seeds. However, primed seeds had higher germination in adverse (35 degrees C) conditions. Seed priming may be used as an important tool to improve carrot seed performance and stand establishment in the field, especially during the summer.