Effects of seed osmopriming on germination of Cynara cardunculus under low, high and optimal temperatures.

The three botanical varieties of Cynara cardunculus (globe artichoke, cultivated and wild cardoon) can be utilized for several uses. Since the cropping system necessitates a good stand to obtain high yield, additional information on seed germination is required. The purpose of this research was to quantify the effects of temperature on the germination of three botanical varieties of C. cardunculus. In addition, seed osmopriming as a means for improving germination performance over a wide range of temperatures was investigated. Seeds were primed in aerated solution at equivalent water potential (-1.2 MPa) of polyethylene glycol (PEG) 6000 or KNO3 + K2HPO4 in a dark room at 18 ± 1 °C for 7 days and then rinsed and dried. The temperature base, optimal and maximum for globe artichoke and cultivated cardoon were, respectively, 4, 16 and 32.5 °C, while for cultivated cardoon were 6.1, 20 and 32.5 °C. The wild cardoon showed a very low germination under all studied temperature, so it was impossible to calculate its cardinal temperatures. Priming in KNO3 + K2HPO4 significantly improved seed germination over a wide range of temperatures in cultivated and wild cardoon, but consistently depressed germination in globe artichoke. Priming with PEG improved germination under low temperatures (4 and 8 °C) in globe artichoke and resulted not significant in cultivated and wild cardoon.