Facultad de Ciencias Químico Biológicas, Universidad Autónoma de Guerrero, Av. Lázaro Cárdenas s/n, Ciudad Universitaria Sur, Chilpancingo de los Bravo, Guerrero, 39086, México.
Licenciatura en Biología, Universidad Autónoma Metropolitana-Iztapalapa, Av. Ferrocarril de San Rafael Atlixco 186, Col. Leyes de Reforma 1ª Sección, Ciudad de México, 09310, México.
Am J Bot. 2022 Aug;109(8):1221-1229. doi: 10.1002/ajb2.16041. Epub 2022 Aug 23.
Terminal velocity (Vt) is an important factor for the dispersal of biological particles but has scarcely been studied for anemochorous fern spores, and the influence of spore characteristics on Vt has not been evaluated. Here, we measured the Vt of 1234 spores of 18 fern species and two Selaginella microspores using videoimaging analysis and evaluated the effects of mass, size, and ornamentation on Vt.
We designed a sedimentation tower with a graduated microtelescope attached to a high-speed video camera to record falling particles and measure the Vt of fern spores using video-image processing software. Spores were measured for each species and their size correlated with Vt.
The Vt of fern spores ranged from 4.7 cm·s (Cyathea costaricensis) to 18.85 cm·s (Acrostichum danaeifolium). The method is accurate and reliable as predicted by Stokes model for glass beads of known density and size. In addition, Vt had a higher correlation coefficient with mass (ρ = 0.72) than size (ρ = 0.20), and ornamental appendages reduced Vt.
The reported values of Vt of fern spores are within the range of different biological airborne particles such as moss spores and pollen grains of seed plants. The results showed that spore ornamentation is directly related to Vt rather than spore size and may increase or decrease the drag. This method will aid future aerobiological research on biological particles.
终端速度（Vt）是生物颗粒扩散的一个重要因素，但对于风媒蕨类孢子几乎没有研究，并且尚未评估孢子特征对 Vt 的影响。在这里，我们使用视频成像分析测量了 18 种蕨类植物和两种卷柏属小孢子的 1234 个孢子的 Vt，并评估了质量、大小和装饰对 Vt 的影响。
我们设计了一个带有附加的微刻度望远镜的沉降塔，将高速摄像机连接到沉降塔上，以记录下落的颗粒，并使用视频图像处理软件测量蕨类孢子的 Vt。我们为每个物种测量了孢子，并将其大小与 Vt 相关联。
蕨类孢子的 Vt 范围为 4.7 cm·s（Cycataea costaricensis）至 18.85 cm·s（Acrostichum danaeifolium）。该方法与已知密度和大小的玻璃珠的 Stokes 模型预测的一样准确可靠。此外，Vt 与质量的相关性系数更高（ρ=0.72），而与大小的相关性系数较低（ρ=0.20），并且装饰性附属物降低了 Vt。
报告的蕨类孢子 Vt 值在不同的生物空气传播颗粒范围内，例如藓类孢子和种子植物花粉粒。结果表明，孢子装饰与 Vt 直接相关，而与孢子大小无关，并且可能增加或减少阻力。该方法将有助于未来对生物颗粒的空气生物学研究。
