准噶尔无叶豆的开花物候与生殖特征

FLOWERING PHENOLOGY AND REPRODUCTIVE FEATURES OF THE RARE PLANT EREMOSPARTON SONGORICUM IN DESERT ZONE,XINJIANG,CHINA

为了研究沙漠稀有植物准噶尔无叶豆（Eremosparton songoricum）的开花物候特征及其对生殖成功的影响，2005和2006年连续两年对其自然种群的开花物候和开花过程中的花部表型变化进行了观察，并运用相对开花振幅、开花强度和开花同步性等开花物候指数研究了开花物候特征。结果表明：准噶尔无叶豆在5月下旬至6月中下旬开花，其种群、个体、花序和单花的花期分别历时26～29d、8～10d、5～7d和2～3d。单花开花进程依其形态和散粉特征可分为散粉前期、散粉初期、散粉盛期和凋谢期4个时期。其个体水平的开花物候进程（开花振幅曲线）呈渐进式单峰曲线，具有很高的开花同步指数，表现出一种集中开花的模式。开花物候指数与座果数之间的相关分析结果表明，始花日期与花期持续时间存在负相关关系，而与开花数和座果数存在正相关关系；花期持续时间与开花数和座果数存在显著正相关关系。准噶尔无叶豆个体开花物候在很大程度上是由其遗传因子决定的，而开花物候在年度间的变异，可能是由于荒漠气候的差异（主要是水分和温度的差异）所引起的。作为沙漠窄域分布特有种，准噶尔无叶豆在环境和人为干扰的双重选择压力下，为了吸引更多的传粉者访问而达到生殖成功，形成了大量集中开花的模式。

Aims Flowering phenology is considered as an important fitness factor because it plays a crucial role in reproductive success. Our aim is to investigate the flowering phenology of Eremosparton songoricum, the 3rd Class national protected dwarf shrub with a fragmented distribution in Gurrbantuggut Desert of Xinjiang, China, to better understand its reproductive features. Methods We marked and observed 30 E. songoricum individuals with similar heights and crown diameters in the wild population of Cainan Oil Station in Gurrbantuggut Desert from 2005 to 2006. We observed the flowering course of each individual and inflorescence including the first flowering date, duration, mean flowering amplitude （flowers plant^-1.d^-1） and last flowering date and then calculated relative flowering intensity and synchrony indices. We also analyzed relationships between first flowering date, median date, duration, last flowering date, flowering amplitude and flowering synchrony, the correlation matrix between first flowering date and duration, flower number and fruit set. Important findings The flowering span of the population, individual, inflorescence and single flowering was approximately 26-29, 8-10, 5-7 and 2-3 d, respectively. None of the phenology index levels between 2005 and 2006 were distinctive. The synchrony index was 0.829. The relative flowering intensity showed one major peak from 10% to 30% and the skewness was 1.24. According to flower morphology and dehiscence, the typical single flowering process for a flower can be divided into four periods： pre-dehiscence, initial dehiscence, full dehiscence and withering. The correlation analysis among the first flowering date, duration, flower number and fruit number shows that 1） there is negative correlation between first flowering date and duration and a positive correlation to flower number and fruit number, 2） duration has a significant positive correlation to flower number and fruit number and 3） there is significant positive correlation between flower number and fruit number. Individuals with more flowers show a longer duration and more fruit than these with fewer flowers. As a rare plant in China＇s desert zone, E. songoricum exhibits a so-called ＂mass-flowering＂ pattern, which may be regarded as an adaptive strategy to ensure its reproductive success.