D'Antraccoli Marco, Roma-Marzio Francesco, Benelli Giovanni, Canale Angelo, Peruzzi Lorenzo
Department of Biology, Unit of Botany, University of Pisa, Via Derna 1, 56126, Pisa, Italy.
Department of Agriculture, Food and Environment, University of Pisa, Via del Borghetto 80, 56124, Pisa, Italy.
J Plant Res. 2019 Mar;132(2):251-261. doi: 10.1007/s10265-019-01090-1. Epub 2019 Feb 13.
After several decades of research, dynamics and patterns of mating system in floral evolution remain incompletely understood, especially with regards to strategies that combine both outcrossing and selfing, as frequently recorded in the genus Campanula. Data about temporal and spatial dynamics of secondary pollen presentation are still scarce in literature: we investigated them using Campanula medium (Campanulaceae) as case study. Experimental pollinations were conducted under natural conditions, to characterise the breeding system of this species. Effects on stigma opening and stigma receptivity of stylar pollen presence were investigated in manipulated flowers. The temporal dynamics and fitness of male and female functional phases were estimated. Flower visitors and their interactions with sexual parts of the flower were also annotated. C. medium is xenogamous and self-incompatible, with a clear temporal separation between sexual functional phases. Floral lifespan is shortened by experimental outcrossing. Removal of pollen from the style shortened the time span of male function. Pollen viability was highest at the beginning of the anthesis, decreasing during the flowering period, whereas stigmatic receptivity shows an opposite trend. We found a severe pollen limitation in the studied population. Bees were the most frequent floral visitors. In some of these insects we observed stereotyped interactions with the reproductive structures of the flower, in particular with the pollen, exposed along the upper and median portion of the style. Sexual phases in C. medium are inversely correlated and finely spatially and temporally coordinated, since stigma maturation is scalar along its length and depends on pollen presence on the style. Overall, our findings push forward the knowledge on reproductive strategies in Campanula.
经过几十年的研究,花卉进化中交配系统的动态和模式仍未被完全理解,特别是对于结合异交和自交的策略,如在风铃草属中经常记录到的那样。关于二次花粉展示的时间和空间动态的数据在文献中仍然很少:我们以风铃草为案例进行了研究。在自然条件下进行了实验授粉,以表征该物种的繁育系统。在人工处理的花朵中研究了花柱上花粉的存在对柱头开放和柱头可授性的影响。估计了雄性和雌性功能阶段的时间动态和适合度。还记录了访花者及其与花的性器官的相互作用。风铃草是异花授粉且自交不亲和的,性功能阶段之间有明显的时间间隔。实验性异交缩短了花的寿命。去除花柱上的花粉缩短了雄性功能的时间跨度。花粉活力在花期开始时最高,在开花期间下降,而柱头可授性则呈现相反的趋势。我们在所研究的种群中发现了严重的花粉限制。蜜蜂是最常见的访花者。在其中一些昆虫中,我们观察到它们与花的生殖结构,特别是与沿花柱上部和中部暴露的花粉,存在刻板的相互作用。风铃草的性阶段呈负相关,在空间和时间上精细协调,因为柱头成熟沿其长度呈梯度变化,并且取决于花柱上花粉的存在。总体而言,我们的研究结果推进了对风铃草属生殖策略的认识。