Caper Capparis spinosa has deep roots, a drought tolerant species, and produces a satisfactory vegetative cover which protects soils from erosion; it can be highly useful for the prevention of land degradation. It is endangered species in its natural habitats in Iran and many other countries due to climate change and overutilization. Domestication of capers as medicinal, vegetable or soil surface coverage plant is complicated by limited and variable seed germination under artificial conditions. In order to examine the role of different levels of KNO3 (0, 500, 1000, 2000, 4000 and 8000 ppm), gibberellic acid (GA3) (0, 50,100, 250, 500, 1000 and 2000 ppm), durations (3, 12, 24 and 48 h) and concentrated sulphuric acid (0.5, 1, 5, 10, 20 and 30 min), on germination of Iranian caper seeds, these experiments were conducted at Physiological Research Laboratory, Ferdowsi University of Mashhad, Iran, in 2010. There was not any symptom of germination of caper seeds in distilled water. Sulphuric acid could not improve the germination properties of caper and some seeds became demolished before the end of the experiment. In general 2000 mg/l gibberellic acid treatment resulted in more vigorous seed germination (42%) at any duration compared to any other concentration of the gibberellic acid. The highest seed germination of 26% was achieved when the seeds were treated 24 hour with 4000 ppm KNO3 solution but it was decreased in 8000 mg/l. The highest germination percentage (72%) was observed in seeds placed in filter papers wetted with in 250 ppm gibberellic acid after treatment with 8000 mg/l KNO3 for 24 h (this duration was the best time span in two previous experiments). It seems that GA3 and KNO3 can replace partly to improve seed germination of caper. The highest radicle length (148 mm) and seedling dry weight was achieved as seeds were treated in 100 ppm gibberellic acid plus 1000 ppm potassium nitrate. Therefore, it can be concluded that for best germination percentage of caper seeds, 250 ppm GA3 and 8000 ppm KNO3 and for the strongest seedling 100 ppm GA3 plus 1000 ppm KNO3 can be used.

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