Osmoconditioning and germination temperatures in seed of two artichoke cultivars

Artichoke seeds germination shows a large variation in emergence rate and germination percentage with reduced uniformity of seedlings. Germination characteristics are negatively influenced by temperatures > 25°C; this condition is usually registered during the sowing season both under greenhouse and open field conditions, thus temporary thermo-dormancy may be induced in seed. Priming techniques allows seeds to germinate more rapidly under unfavourable environmental conditions and it has been shown to be an effective method to overcome thermo-dormancy in several vegetable species. This work examines osmoconditioning, using a solution of polyethylene - glycol (PEG), to fasten and synchronize the germination of artichoke achens. Seeds of two artichoke cultivars: '137' (hybrid) and '044' (open-pollinated) were used. A solution of PEG 8000 was employed as osmoticum for seed priming with water potential equal to 1 MPa at 20°C. The seeds were primed inside Plexiglass boxes (110×80×60 mm) on two filter papers at 100% RH to prevent loss of water. Two temperatures of germination (22 and 35/25°C), 2 cultivars and 4 priming timings (0, 7, 12 and 17 d) were used. Priming treatments influenced negatively the germination characteristics of "seeds". Germination of '137' was higher and faster; starting and ending earlier than that of '044'. The higher temperature regime during the germination reduced the germination percentage and retarded the beginning of germination by 3 d. Increasing priming duration decreased germination percentage.