宁夏枸杞的花粉呈现式样及交配系统研究

Pollen Presentation and Mating System of Lycium barbarum

被子植物的花回馈、雌雄蕊时空分离特征和花粉呈现式样等花部特征及传粉者效率会影响雄性适合度和有性繁殖过程。宁夏枸杞(Lycium barbarum)是中国宁夏、新疆、内蒙等干旱和半干旱地区分布的特有种。该研究对新疆喀什地区宁夏枸杞自然种群的花部综合征、花粉呈现式样、花回馈、传粉者行为与交配方式的关系进行观察及统计分析,以探讨其花粉逐步呈现的适应性及其在提高雌雄繁殖过程中的意义。结果表明:(1)宁夏枸杞的单花寿命为(4.07±0.15) d,而雄性持续时间(0.07±0.01 d)比雌性持续时间短(4±0.01 d);花寿命内雌蕊长度比雄蕊长,属柱头探出式异位类型;花粉呈现式样为不完全逐步呈现。(2)花寿命不同阶段花回馈间存在显著差异。(3)意大利蜜蜂(Apis mellifera)、熊蜂(Bombus sp.)、食蚜蝇(Syrphidae sp.)是宁夏枸杞在自然居群的主要访花者,其中熊蜂和食蚜蝇是主要传粉者,但传粉者效率低,属于高移出低沉积类型。(4)宁夏枸杞的花粉胚珠比(2 448.11±448.32)及授粉实验结果均表现出兼性异交特征;自发自交及人工自花授粉花的座果率及结籽率很低,属于自交不亲和类型;自然传粉花的座果率及结籽率比人工去雄异花低,存在其较高的花粉限制(40.71%)。研究发现,宁夏枸杞花部综合征表现出雌雄异位和花粉不完全逐步呈现式样,这是避免雌雄功能及雄蕊各花药间的干扰、减少花粉同步移出及保障其雄性适合度的有效途径,但自然居群的传粉者种类限制、传粉效率低以及自交不亲性是导致宁夏枸杞花粉限制及降低雌性繁殖成功的主要原因。

In flowering plants, male fitness and sexual reproduction are influenced by floral characteristics, floral reward, distance between pistils and stamens, pollen presentation, and pollinator efficiency. Lycium barbarum L. is a species in arid and semi-arid areas, such as Ningxia, Xinjiang, and Inner Mongolia, China. We observed and analyzed the relationships between floral characteristics, pollen presentation pattern, floral reward, and pollinator behavior within the mating system of L. barbarum in Kashi, Xinjiang. Our results showed that:(1) the floral longevity was(4.07±0.15) d. The duration of the male stage(0.07±0.01 d) was shorter than that of the female stage(4±0.01 d), which was indicative of herkogamy. Additionally, the pollen-presenting pattern showed incomplete gradual presentation.(2) Floral reward differed significantly among flowering stages.(3) Apis mellifera, Bombus sp., and Syrphidae sp. were the main flower visitors;the latter two, which were the main pollinators, showed high removal and low deposition of pollen.(4) The pollination experiment and pollen-ovule ratio(2 448.11±448.32) revealed facultative outbreeding characteristics. The low fruit and seed-setting rate from spontaneous autogamy and manual self-pollination indicated that the species was self-incompatible. The seed-setting rate from natural pollination was lower than that from cross-pollinated flowers, and the species had a high pollen limit(40.71%). In conclusion, L. barbarum floral characteristics shows herkogamy and incomplete gradual pollen presentation, which is an effective strategy for avoiding interference between male and female floral functions, reducing the synchronous removal of pollen and ensuring male fitness. However, high removal-low deposition pollinators, low pollination efficiency, and self-incompatibility in natural populations are the primary reasons for pollen limitation and female reproductive success in L. barbarum.