Natural Release Patterns And Artificial Breaking Of Seed Dormancy In 3 Desert Plant Species

Most desert plants seeds have dormancy which can avoid seed germination in risk environments to ensure seedlings survive. So, seed dormancy plays an important role in vegetation reconstruction. The objectivies of present study were to investigate suitable methods of seed dormancy breaking and effects of depth and duration of burial in the field on germinability, dormancy and longevity of 3 desert plant species. The species were Lespedeza potanimii Vass., Nitraria tangutorum Bobr. and Pegamum nigrllastrum Bunge. The field burial experiment were conducted during a 18-month period in the site of the original seed collection.The results showed that:1 Sulfuric acid, hot water and liquid nitrogen were all effective techniques of dormancy breaking in 3 seed lots of L. potanimii, and the responses of seed lots to sulfuric acid, hot water and liquid nitrogen were different.The treatment of sulfuric acid with 25-30 min was the best method to break dormancy for all seed lots.2 After treated with GA and cold stratification, seed dormancy of N. tangutorum was significantly breaked, and the germination percentage increased to 66% in the optimum GA concentration (150ug/g).The best treatment for seed dormancy breaking is placing the seeds in 4℃for 4 weeks, and the germination percentage were increased to 88%.3 The optimum temperature for germination of P. nigrllastrum seeds was 25/35℃(high temperature 8h,low temperature 16h).4 The results of field bruial experiment showed that:the field germination percentage increased with the buried depth rising. After 18 months burial, the maximum field germination of L.potanimii, N. tangutoruma and P. multisectum were 15%,26% and 12%, respectively. The field germination mainly occurred in April to October when the precipitation was higher.5 The dormancy release patten were different with each other in the three species. The innate dormancy percentage of L. potanimii seeds decreased from initial 98%to 64% on the soil surface (0 cm), but less change was observed when buried at 2 cm,5 cm and 10 cm. Although a high level dormancy in N. tangutorum when seed were harvested, its innate dormancy percentage decreased from 94% to 1% after 4 months burial in the field.Contrary to above two species, P. multisectum seeds exhibited seasonal pattern (dormancy cycle)during experimental period. The maximum points of innate dormancy in two years were observed in October,decreasing thereafter.6 The decayed seeds decreased with the buried depth rising,but increased with the buried duration rising. The maximum decayed seeds percentage of 3 species are 3.5%,31% and 12%, respectively. The loss of seeds indicated that the 3 species all behaved as persistent soil seed bank according to Thompson's system(1979).