Studies On Propagation Biology And Population Structure Of The Rare Plant Pteroceltis Tatarinowii Maxim

Pteroceltis tatarinowii Maxim, a species of the genus Pteroceltis in the family Ulmaceae, endemic to China, is considered an endangered plant on the brink of extinction. It is of high value not only in utilization in fibre, medicine, timber, nutrition, but also in the eco-protection and scientific research. At present, the Pteroceltis tatarinowii resources are decreasing quickly, thus, it has been listed as a member of the national gradeâ…¢rare and endangered plants. Up to date, however, the study on endangered mechanism of this species is still unknown. Therefore, this study focuses on these issues with respect to morphology , anatomy, propagation biology, population structure, and distribution pattern of this species. According to the results from this study, the factors that caused the present dangerous situation of Pteroceltis tatarinowii have been analyzed and several measures for effective protecting have also been proposed. The conclusions are as follows:1. The seed of Pteroceltis tatarinowii is dormant. The potential ability of germination (86.7%) by the method of TTC, is much higher than its effective level of germination (19.2%) in its habitat soil. This result is consistent with few seedlings in its natural habitats through our investigation. The reasons resulting in obvious decline of germination rate may be the sensitiveness of Pteroceltis tatarinowii to the conditions of germination, especially seed coat and microorganism in soil being the two key affecting factors.2. Physiological after-ripping and chemical inhibitors in seed were two principal reasons which cause the dormancy. By soaking the seed in 300mg/l GA3 solution for 24h or in GA3 solution following cold stratification cound overcome the dormancy of seed. The optimal measure was that soaking the seed in 500mg/l GA3 solution for 36h following cold stratification for 25d, with the percentage of germination and germination power of 83.5% and 65%.3. The leaves of Pteroceltis tatarinowii were used as explants for tissue culture for callus induction and propagation on MS with NAA and 6-BA. The optimal medium for callus induction from leaves was MS, supplied with 0.5 mg/l NAA and 1.0 mg/l 6-BA. To culture firstly in dark for 7 days was better for inducing callus in the medium. The designed adventitious buds induction culture medium was not suitable for this species. NAA had evident effect for root induction.4. The anatomical structure of leaves adopt well to the dry and poor limestone area. The drought resistance of Pteroceltis tartarinowii Maxim from the population of Ying Ping hill in which habitat was the poorest was the strongest. The leaves had xeromorphic characteristics, including thickened leaves, thickened epidermis cell wall and cuticle, well developed palisade tissue, densely arranged cell. Small and dense stomata and distribute in cluster etc. These character could be derived from the result of adaptation to unfavorable environments of limestone area, such as poor soil and water menace.5. The population structure of Pteroceltis tartarinowii at 8 plots in Langya mountain National Forest Park presented senescent or adult type, infant seedlings and big trees were thimbleful, most of size classes were concentrated on saplings and median and its populations appeared to recession trend in general. All but one populations were performed the pattern of clustering distribution. With the population age increased, the distribution pattern had a trend from clustering to random, the clustering intensity decreased somewhat. The analysis showed that the spatial distribution pattern of Pteroceltis tatarinowii populations were related to its biological and ecological characteristics, community composition, environmental factors, and the competitive exclusion principle. Varies plot sizes had also an effect on spatial distribution pattern.6. From above-mentioned analyses we know that the patchy and heterogeneous, the intense disturbance from human and strong interspecies competitions, high death rate of seedling are the main cause leading to the endangering of Pteroceltis tatarinowii. The following procedures should be taken to protect Pteroceltis tatarinowii from extinction, viz., protection of favorable habitats, prevention of strong disturbance from human, reconstruction population size, ex-situ conservation and enhancing inter-population genetic exchange. because of its biological and ecological characteristics, community composition, environmental factors and human disturbance.