The Reproductive Ecology Of Eremosparton Songoricum (Litv.) Vass

Eremosparton songoricum(Litv.)Vass(Fabaceae), a plant species that only occurs in Gurrbantuggut desert of China, is listed in the China Red Data Book as 3 Class national protected plants. In this paper, we observed the flowering phonology, characteristics of breeding system and seed germination in the wild population of Cainan oil station and Town Kalabulegen in Gurrbantuggut desert, Xinjiang Province. The main rusults were as follows:1.Flowering phenology: the flowering span of the individuals is about 8~10days. The individuals'time courses of flowering were similar in 2005 and 2006, the proportion of open flowers increased rapidly to a peak and then declined rapidly over the subsequent days. The synchrony index is 0.829. The relative flowering intensity shows one major peak: from 10% to 30% and skewness ratio is 1.24. This phenomenon is consistent with some other studies E. songoricum flower lasts 2 to 3 days. The analysis of individual phonological data between the two years shows that, there are no differences of the first flowering date, the median date, relative flowering intensity and synchrony, but apparent differences between duration and last flowering date. However the individuals have the similar flowering amplitudes curves in two years, which reflects that the differences maybe aroused by the changeableness of desert climate.The correlation analysis among the first flowering date, duration, flower number and fruit number shows :1).there is negative correlation between first flowering date and duration, however, it has the positive correlation to flower number and fruit number. 2).duration has significant positive correlation to flower number and fruit number.3). there is significant positive correlation between flower number and fruit number. The individual with more flowers shows a longer duration and more fruit number than these with less flowers. There is higher fruit number in the individuals with more flower number and longer duration than in the individuals with less flower number and short duration.As a rare plant to China desert zone, E. songoricum exhibits a so-called"Mass- flowering"pattern, which may be regarded as an adaptive strategy to ensure its reproductive success.2.Flower morphology characteristics and breeding system: The flower of E. songoricum has both self-pollination and cross pollination characteristics, as regards flower morphology and dehiscence,the typical flowering process for a flower can be divided into 4 periods, i.e.,"Pre-dehiscence","Initial dehiscence","Full dehiscence"and"Withering". Its out-crossing index is 3,the pollen grain number per flower is 11160. The ovule number is 8-10, so the pollen-ovule ratio is 1116-1395. According to the Danfi judgement, the type of breeding-system is out-crossing self-compatible, sometimes demanding for pollinators. Bees are the main daily pattern of fly visitation to E. songoricum at anthesis. E. songoricum processing the mixed breeding system is a kind of compromised mechanism which adapts to the environmental condition and plant itself. But the lackness of pollinators, low pollination efficiency as well as the superiority of self-flower pollen in the pollen competition has caused low seed setting rate in reproduction. These primary factors make it endangered in reproduction.3. Seed germination: The germination characteristics of big and small E. songoricum seeds under thee lights and five temperatures conditions were studied. The results showed that the 1000-grain weight of big seed is 21.50±1.24g and the 1000-grain weight of big seed is 15.47±1.02g. The optimal light condition is 12/12h light/dark and no difference was found between the germination of big and small seeds in light and in darkness. The optimal temperature range for germination was 20℃~25℃, yielding maximum germination and germination index. Big seeds have physical dormancy and small seeds not only exist physical dormancy but also may have the other dormancy. The germination of E. songoricum seeds in the nature is very low(≤3%). After analysis, we considered that the hardness of seeds and other dormancy were mainly reason for low germination,however,the light,temperature and soil humidity are not the restriction in E. songoricum germination.Considering from the reproductive ecology aspects, we suggest that:1). Strengthen the E. songoricum habitat protection and reduce the artificial destruction to slow down the tendency of E. songoricum population fragment distribution and to enhance its reproductive success ratio;2).when it has mass-flowering we should breed the bee class insects in the protection population which increases the quantity of pollinator and enhances the pollination efficiency;3). In artificial reconstruction and in the process of seedlings, take a set of management to offer the best seed germination environment and the seedling habitat condition.