Effect of dry-heat, soaking in distilled water and gibberellic acid on the germination of Cistus clusii, C. monspeliensis and C. salvifolius seeds

Different pretreatments for promoting germination of Cistus clusii, C. monspeliensis and C. salvifolius, Cistaceous species widely distributed in Mediterranean region, were investigated. Pretreatments applied were: dry-heat, seed soaking in distilled water and gibberellic acid. Germination tests were performed under controlled conditions at 15°C in darkness. Dry-heat treatments were shown to break dormancy. The highest germination percentages in the three species studied were obtained with dry-heat at 100°C for five minutes. Dry-heat at 80°C for a longer exposition times was only effective for C. clusii and C. salvifolius. These results indicated that hardness and impermeability of seed coats to water uptake might be the most important cause of the dormancy present in seeds of C. clusii, C. monspeliensis and C. salvifolius, as in other Cistus species. The soaking of seeds in distilled water and exogenous gibberellic acid applications did not significantly increase germination over untreated seeds.