高山植物全缘叶绿绒蒿在不同海拔地区的传粉生态学研究

Pollination ecology of alpine herb Meconopsis integrifolia at different altitudes

为了探明高山植物全缘叶绿绒蒿(Meconopsis integrifolia)的繁育系统特点和其对高山气候环境的繁殖适应特征,我们沿海拔梯度选择了5个样地(样地1(4 452 m)、样地2(4 215 m)、样地3(4 081 m)、样地4(3 841 m)、样地5(3 681 m))对其传粉生态学进行了连续2年的观察试验。结果发现,样地1、2的全缘叶绿绒蒿的单花寿命显著长于样地3、4和5。花开放早期柱头高于花药,之后花药不断伸长,并在开放中后期与柱头接触,说明全缘叶绿绒蒿具有不完全雌雄异位的花部特征。自然状态下,柱头可授能力持续期约8天(雌蕊先熟),但花药于开花第5天才散粉,花粉寿命约2天,说明全缘叶绿绒蒿为雌雄异熟,但存在一定的重叠期。人工授粉试验表明,全缘叶绿绒蒿自交部分亲和,且不存在无融合生殖现象。各样地中自然对照的结实率显著低于人工异交处理的结实率,说明自然状态下全缘叶绿绒蒿存在一定程度的传粉限制。传粉昆虫观察发现,样地1和2的传粉昆虫主要是蝇类,样地3、4和5的传粉昆虫主要是蝇类和蓟马(Thripidae spp.),蝇类在不同植株间的活动能够保证异花传粉结实,同时,蝇类和蓟马在花内的活动会引起"协助自交"。全缘叶绿绒蒿约65%的观察个体存在"自动自交"。蝇类在各样地的访花频率存在显著差异,样地1访花频率最低,样地2访花频率最高。各样地的结实由于异花传粉者的不足而受到传粉限制。两种不同类型的自交机制恰恰为该植物异花传粉者不足提供了一定程度的繁殖补偿。全缘叶绿绒蒿不分泌花蜜,当环境温度降低时,采取为昆虫提供保温庇护场所的方式来吸引传粉者。

Aims We studied the breeding system and pollination ecology of Meconopsis integrifolia（Papaveraceae）,which is an alpine herb,for two consecutive years. Methods Five plots（plot 1,4 452 m a.s.l; plot 2,4 215 m a.s.l; plot 3,4 081 m a.s.l; plot 4,3 841 m a.s.l; plot 5,3681 m a.s.l） were established along an altitudinal gradient in the Balang Mountain. Flower longevity,stigma height and the highest stamen were measured and recorded. The stigma receptivity and pollen viability were tested by the Benzidine-H2O2 method and the TTC method,respectively. The breeding system was tested by experimental approaches,and flower visitors were observed over the life span of the flower. The temperatures of the flower and environment were also recorded. Important findings Flower longevity was greater in plots 1 and 2 than in plots 3,4 and 5. The stigmas were higher than the anthers at the beginning of anthesis,and the distance between stigmas and the anthers then gradually decreased with the progress of flowing. The stigmas and anthers came into contact when the corolla wilted in 65% of the flowers sampled,indicating an incomplete herkogamy. The stigmas became receptive before the dehiscence of anthers（protogyny）. Under natural conditions,stigma receptivity lasted for 8 d and pollen viability lasted for 2 d. Hand-pollination experiments indicated that M. integrifolia was self-compatible and did not exhibitapomixis. Seed set was significantly increased after a supplemental hand-pollination,suggesting the pollen-limitation of reproduction. The pollinators in plots 1 and 2 were flies,and in plots 3,4 and 5 flies and Thripidae spp. We observed that flies moved and transferred pollen between plants,and that both flies and Thripidae spp. moved within flowers,the latter resulted in ＂facilitated selfing＂. About 65% of the plants sampled set seed by autonomous self-pollination. There was a significant difference in the visiting frequency of flies between plots,with plot 1 being the lowest and plot 2 the highest. Pollen limitations were evident across all plots due to lack of sufficient outcrossing pollinators. Two different selfing mechanisms,unexplored here,may provide a partial compensation for the natural reproduction of this alpine species in the arid,alpine habitats. M. integrifolia could attract pollinators by providing a warm shelter.