Department of Botany and Biodiversity Research, Division of Structural and Functional Botany, University of Vienna, Austria.
VetCORE - Facility for Research, University of Veterinary Medicine Vienna, Vienna, Austria.
J Exp Bot. 2018 Jan 23;69(3):525-535. doi: 10.1093/jxb/erx405.
The flower is a bisexual reproductive unit where both genders compete for resources. Counting pollen and ovules in flowers is essential to understand how much is invested in each gender. Classical methods to count very numerous pollen grains and ovules are inefficient when pollen grains are tightly aggregated, and when fertilization rates of ovules are unknown. In this study we have therefore developed novel counting techniques based on computed tomography. In order to demonstrate the potential of our methods in very difficult cases, we counted pollen and ovules across inflorescences of deceptive and rewarding species of European orchids, which possess both very large numbers of pollen grains (tightly aggregated) and ovules. Pollen counts did not significantly vary across inflorescences and pollination strategies, whereas deceptive flowers had significantly more ovules than rewarding flowers. The within-inflorescence variance of pollen-to-ovule ratios in rewarding flowers was four times higher than in deceptive flowers, possibly demonstrating differences in the constraints acting on both pollination strategies. We demonstrate the inaccuracies and limitations of previously established methods, and the broad applicability of our new techniques: they allow measurement of reproductive investment without restriction on object number or aggregation, and without specimen destruction.
花是一个两性生殖单位，两性之间为争夺资源而竞争。统计花中的花粉和胚珠对于了解两性各自的投资至关重要。当花粉粒紧密聚集或胚珠受精率未知时，传统的方法对大量花粉粒和胚珠进行计数效率低下。因此，本研究基于计算机断层扫描开发了新的计数技术。为了展示我们的方法在非常困难情况下的潜力，我们对欧洲兰花的欺骗和奖赏物种的花序中的花粉和胚珠进行了计数，这些物种的花粉粒数量非常多（紧密聚集），胚珠数量也非常多。花粉粒计数在花序和授粉策略之间没有显著差异，而欺骗花的胚珠数量明显多于奖赏花。奖赏花中花粉与胚珠比值的花序内方差是欺骗花的四倍，这可能表明两种授粉策略受到的限制不同。我们证明了以前建立的方法的不准确性和局限性，以及我们新技术的广泛适用性：它们允许在不受物体数量或聚集限制的情况下，在不破坏标本的情况下测量生殖投资。
