Studies On Seed Germination And Drought Resistancy Of Xeric Landscape Plants

Sustainable Xeriscape Gardening is the first choice for the cities with severe water shortage problem. Xeric landscape plants is the most important constituent for the garden construction. However, many of the xeric plants encountered the problems of slow seedling establishment due to low seed germination or seed dormancy, which has become the main obstacles for the more wide spread use of the plants. In this research, an effort was made to investigate the seed germination behaviourr of a number of selected xeric plants and to test the drought resistancies of the seeds in rder to releviate the difficulty of seedling establishment.Based on the seed germination test, it was found that most of the seeds were orthodox seeds capable of germinating under a wide range of temperature range. Three of the plants, Allium Mongolicum, Allium polyrhizum and Linum perenne. had the problems of seed dormancy. The dormancy types of Allium Mongolicum and Linum perenne were physiological dormancy. Threatments such as pre-chilling, soaking with plant hormone solutions could effectively break the dormancy of the two specise. Seed dormancy of Allium polyrhizum belong to the post-maturation type which could be released after one years natural storage.Seed germination tests were conducted to select the optimal condition (combination of temperature, illumination and germination-bed) for the seeds. The results showed that, for most of the seeds, the most suitable germination temperature was 20-25 ℃ constant temperature. But several seeds perfer lower temperature or higher temperatures for germination.15℃ constant temperature is the most suitable germination temperature for Allium Yuchuanii seed.30 ℃ constant temperature is the most suitable germination temperature for Melandrium album and Dianthus chinensis. In the germination process, the light had negative effects for the seeds of Allium, Asteraceae and Rosaceae. Seed germination of Allium tuberosum, Pottella chinensis and Ajania pallasian were not affected by light condition. Top-Paper and Between-Paper germination bed are better choice for most of tested seeds. Top-Sand germination bed is better choice for Pottella chinensis, Heteropappus altaicus, Scabiosa atropurea and Aquilegia glandulosa. Between-Sand germination bed is the worst choice for all the test seeds.The PEG-6000 solutions of different concentrations were used to imitate different levels of drought stress. Seeds germinated under the stresses showed the different drought-resistant abilities. The results showed that, Allium polyrhizum is extremely sensitive to moisture conditions. Mild drought stress will cause serious influence on it. Heteropappus altaicus, Pottella chinensis and Potentila bifurca can resist moderate drought stress. All the tested seeds can not resist the severe drought stress. A certain degree of drought stress can improve the seed germination performance of Arabis pendula var. hypoglauca, Pottella chinensis, Potentila bifurca and Viola philippica Cav. by increasing seed germination rate, accelerating germination speed, or improving the germination uniformity.