The Study On Germination Characteristic Of Lamiaceae And Brassicaceae Species From The Eastern Qinghai-Tibetan Plateau

Seed mass and seed germination behaviors were the key characters to species update in community, affecting the community structure and dynamics. Light was an importantly environmental factor affecting seed germination behaviors. Light was a signal stimulus, which influenced seed germination by stimulating or inhibiting seed dormancy.We studied the relationship between the seed mass and germination characteristics of Lamiaceae under the natural condition of the wild. We also studied the effects of light gradient on germination of Lamiaceae and Brassicaceae plants. The seeds were collected from the eastern Tsinghai-Tibet Plateau. The results demonstrated that:(1) The range of seed mass was from 0.0061 to 0.5688 g and the average was 0.1200 g. Almost the seed weight of 60% species was less than 0.1200 g, illuminating that small seeds of Lamiaceae plants were common in the eastern Tsinghai-Tibet Plateau.(2) Germination percentage and germination rate were significantly and negatively related to seed mass (P<0.01). The correlation between seed mass and germination concentration degree was most significantly positive (P<0.001). The correlation between seed mass and days to first germination was not significant. According to these results we found that there were two opposite germination strategies between large seeds and small seeds of 24 Lamiaceae plants. Small seeds had higher germination percentage, higher germination rate, shorter germination duration and lower germination concentration degree, which was opposite to large seeds. Large seeds and small seeds constituted a continuum from small-seeded species (colonization) to large-seeded species (competition) with their dispersal ability, which can explain the issues how were the large and small seeds plants coexist in the same natural community by the strategy of seed germination.(3) According to the results from principle component analysis of germination characteristics, 24 Lamiaceae plants showed four germination patterns:rapid, slow, intermediate and low germination. Among these four germination patterns, most species chose the rapid and low germination patterns, the reasons were that they could avoid the harsh natural conditions in the alpine region, which can decreased the death rate, or make a wide range of species distribution in different regions, which can maintain a certain populations.(4) There was not a significant correlation between light gradient and germination rate for 28 species of Lamiaceae and Brassicaceae(P>0.05). Days to first germination of species between full light (100% NS) and severe shade (3% NS) was significantly (P<0.05). There was a most significant correlation (P<0.001) between light gradient and mean time to germination. As light intensity decreasing, the mean time to germination time of species reduced, indicated that light prolonged the germination time.(5) Under three light gradients, the different germination rates between annual or biennial plants and perennials were significant (P<0.05). The seed germination rate of annual or biennial plant was significantly lower than that of perennials. Under three different light gradients, the different days to first germination and mean time to germination between annual or biennial and perennial plants were not significant (P>0.05).(6) Under three light gradients, the different germination rate and germination concentration degree of plants between south slope and north slope were not significant (P>0.05); the different days to first germination of plants between south slope and north slope were significant (P<0.05) in three light gradients. The days to first germination of plants in north slope were later than that of plants in south slope.