浙江低山地区多用途植物无患子的开花物候特征

无患子(Sapindus mukorossi Gaertn.)是我国长江以南地区传统的重要绿化树种,其果皮富含皂苷,种仁富含油脂,是国家林业局审定的新型木本油料树种之一。为研究多用途树种无患子在浙江低山地区的开花特征,2012年和2013年连续两年对位于浙江省天台县9年生无患子人工林在群体、个体、花序和单花水平进行开花物候观测和比较,并运用开花日期、相对开花强度和同步性等指数研究了无患子开花物候特征。观察结果显示:无患子花呈浅黄白色,花的类型有雄花和两性花,没有发现雌花。雄花较两性花大(花径分别为5.09 mm和3.72 mm),雄蕊多为8枚,个别7或9、10枚;雌蕊退化仅留下浅绿色凸起。两性花花萼稍抱拢,花药藏于花被片下,雄蕊大多8枚,极少数7枚或9枚,柱头高于花药并伸出花苞,子房一般具3室,极少数4室或仅2室。无患子2012年的开花进程略早于2013年,其花期集中在在5月中旬至6月上旬,单花从花蕾膨大到花朵凋谢一般为8—9 d。在2012年和2013年,无患子在群体、个体和花序水平的花期约为30 d、20 d、11 d和28 d、19 d、13 d。个体水平的开花振幅均呈单峰曲线,年际间相似性较高;开花同步性在个体水平同步性较高(同步指数为0.868),表现出一种大量、集中的开花式样;相对开花强度在单株间分布范围相对宽泛,但主要分布在30%—40%,在年际间和年际内均呈现极显著差异。花期同步指数在两年的变异范围分别是0.81—0.97和0.70—0.98,不同单株开花同步性在年际内差异极显著,但在年际间差异性则不显著。由此可见,无患子的生殖资源分配存在明显的时空差异,较长的花期可以减少非法花粉的干扰、保持其种群基因多样性,遗传因子是决定无患子开花物候的主要因素,生态环境对无患子开花物候的影响还需进一步研究,本研究以期为探索无患子开花的主要限制因子奠定基础。

Flowering phenology of the multipurpose tree species Sapindus mukorossi Gaertn. in low mountain areas of Zhejiang Province

Sapindus mukorossi Gaertn. is a traditional and important virescent tree species in southern China with peel and seed oil rich in saponins. This tree species is one of the newly developed woody-oil species approved by the State Forestry Administration of China. To investigate the flowering phenology and characteristics of this multipurpose tree species, we observed and compared 9-yr-old plantations of S. mukorossi at population, individual, inflorescence, and single-flower levels in Zhejiang Province, Tiantai County, from 2012 to 2013, based on the first flowering date, relative flowering intensity, flowering synchrony, and so on. The results showed that the flower color of S. mukorossi was yellowish white and the flowers were either male or bisexual. The male flower (5.09 mm in diameter) was larger than the bisexual flower (3.72 mm in diameter). There were usually eight stamens in the male flower; however, a few flowers had seven, nine, or ten. The pistil of the male flower was degenerated and only a slight, light-green protuberance was preserved. The calyx of the bisexual flower folded together lightly and the anthers were under the perianthes. There were generally eight stamens in the bisexual flower, but some also had seven or nine. The chapiter was higher than the anther and was outside the bud. Generally, the ovary had three chambers, but had two or four in rare cases. S. mukorossi flowered earlier in 2012 than in 2013, and the flowering period of the test populations was from the middle of May to late June. The development of the single flower was 8-9 d long from the flower bud to wilting stages. In 2012 and 2013, the florescences of the population, individuals, and inflorescences were approximately 30, 20, and 11 d, and 28, 19, and 13 d, respectively. The flowering amplitude of individuals and inflorescences showed a single peak, sharing a high similarity from year to year. The temporal patterns of flowering of S. mukorossi were very similar at the population level, with a well-defined peak and marked synchrony. The index of synchronicity was about 0.868. The relative flowering intensity was distributed over a wide range, but was concentrated between 30% and 40%. The flowering intensity showed an extremely significant (P=0.01) correlation annually and over different years. The range of variation of flowering synchrony was 0.81-0.97 and 0.70-0.98 in 2012 and 2013, respectively. The flowering synchrony correlation was extremely significant (P=0.01) annually, but not in different years. This suggested that there were temporal and spatial differences in the allocation of S. mukorossi reproductive resources, with longer flowering periods and higher flowering synchronization. Long flowering periods can alleviate the interference of illegal pollen and maintain population gene diversity. Heredity is the main factor affecting flowering phenology in S. mukorossi populations. The effects of ecological and environmental factors on flowering phenology need to be researched further.