Zanatta Florian, Patiño Jairo, Lebeau Frederic, Massinon Mathieu, Hylander Kristofer, de Haan Myriam, Ballings Petra, Degreef Jerôme, Vanderpoorten Alain
Department of Conservation Biology and Evolution, Institute of Botany, University of Liège, Sart Tilman, Liège, Belgium
Department of Conservation Biology and Evolution, Institute of Botany, University of Liège, Sart Tilman, Liège, Belgium Island Ecology and Evolution Research Group, Instituto de Productos Naturales y Agrobiología (IPNA-CSIC), La Laguna, Tenerife, Canary Islands, Spain.
Ann Bot. 2016 Aug;118(2):197-206. doi: 10.1093/aob/mcw092. Epub 2016 Jun 13.
The settling velocity of diaspores is a key parameter for the measurement of dispersal ability in wind-dispersed plants and one of the most relevant parameters in explicit dispersal models, but remains largely undocumented in bryophytes. The settling velocities of moss spores were measured and it was determined whether settling velocities can be derived from spore diameter using Stokes' Law or if specific traits of spore ornamentation cause departures from theoretical expectations.
A fall tower design combined with a high-speed camera was used to document spore settling velocities in nine moss species selected to cover the range of spore diameters within the group. Linear mixed effect models were employed to determine whether settling velocity can be predicted from spore diameter, taking specific variation in shape and surface roughness into account.
Average settling velocity of moss spores ranged from 0·49 to 8·52 cm s(-1) There was a significant positive relationship between spore settling velocity and size, but the inclusion of variables of shape and texture of spores in the best-fit models provides evidence for their role in shaping spore settling velocities.
Settling velocities in mosses can significantly depart from expectations derived from Stokes' Law. We suggest that variation in spore shape and ornamentation affects the balance between density and drag, and results in different dispersal capacities, which may be correlated with different life-history traits or ecological requirements. Further studies on spore ultrastructure would be necessary to determine the role of complex spore ornamentation patterns in the drag-to-mass ratio and ultimately identify what is the still poorly understood function of the striking and highly variable ornamentation patterns of the perine layer on moss spores.
传播体的沉降速度是衡量风媒植物扩散能力的关键参数，也是明确扩散模型中最相关的参数之一，但在苔藓植物中仍基本未被记录。我们测量了苔藓孢子的沉降速度，并确定是否可以使用斯托克斯定律从孢子直径推导出沉降速度，或者孢子纹饰的特定特征是否会导致与理论预期的偏差。
采用结合高速摄像机的落体塔设计，记录了从该类群中选取的9种苔藓的孢子沉降速度，这些苔藓的孢子直径范围涵盖了整个类群。采用线性混合效应模型，在考虑形状和表面粗糙度的特定变化的情况下，确定是否可以根据孢子直径预测沉降速度。
苔藓孢子的平均沉降速度在0.49至8.52厘米/秒之间。孢子沉降速度与大小之间存在显著的正相关关系，但在最佳拟合模型中纳入孢子形状和纹理变量，为它们在塑造孢子沉降速度方面的作用提供了证据。
苔藓的沉降速度可能会显著偏离根据斯托克斯定律得出的预期。我们认为，孢子形状和纹饰的变化会影响密度和阻力之间的平衡，并导致不同的扩散能力，这可能与不同的生活史特征或生态需求相关。有必要对孢子超微结构进行进一步研究，以确定复杂的孢子纹饰模式在阻力与质量比中的作用，并最终确定苔藓孢子周壁层引人注目的高度可变纹饰模式仍未得到充分理解的功能是什么。
