[B-BG01] Earth and Planetary Science Frontiers for Life and Global Environment

[BBG01-09] Effect of Humidity on Maize Pollen Falling Velocity

*Karen Yamada^1,2, Arii Yasumoto^3,2, Naoya Katsuhama^4,2, Rimpei Katada^5,2, Shigeru Fujita^6,2, Asahi Hashimoto^7,2, Nobuyasu Naruse^8,2, Yukihiro Takahashi^9,2 (1.Tokyo Metropolitan Hakuo High School, 2.Super Scientist Program Plus, 3.College of Asia Pacific Studies, Ritsumeikan Asia Pacific University, 4.Graduate School of Agriculture, Forestry and Fisheries, Kagoshima University, 5.School of Agriculture, Meiji University, 6.Department of Veterinary Medicine, College of Bioresource Sciences, Nihon University, 7.College of Geoscience, University of Tsukuba, 8.Faculty of Medicine, Shiga University of Medical Science, 9.Graduate School of Science, Hokkaido University )

Keywords:pollen falling velocity, relative humidity, Stokes' Law, maize

By measuring the falling velocity of pollen from anemophilous crops such as maize, we can estimate the dissemination area and distance of wind-borne pollen. Prior research measured the falling speed of maize pollens under the condition of a wind tunnel. However, these studies have only considered the effect of wind speed and temperature and did not clearly state air humidity as a variable of the falling speed. Humid air can increase the size and weight of pollen, which could affect its falling speed. Studying the effect of humidity on pollen dispersal will contribute to the accurate quantification of airborne pollen.

In this study, we investigated the relationship between humidity in the air and the falling seed of pollen. We measured the falling velocity of pollen kept under a certain level of humidity. We also observed the variance of shapes and weights of pollen by the humidity to discuss the cause of change in its velocity.

We dropped maize pollen under different humid air and photographed it with a digital single-lens camera. Using image processing software, we calculated the falling speed and size of the pollen particle from the video captured.

In the observation, we started with measuring the falling speed of flour to verify the effectiveness of our method. We used flour which has a 1.5 times larger average size than that of maize pollen before changing the humidity. The falling flour was photographed with a digital single-lens camera placed at a distance of 70 cm apart. The speeds and the sizes were measured from the image trace of the particle using image processing software. To evaluate the reliability of experimental data, the relationship between the falling speed and the particle size was also calculated using the settling velocity equation, Stokes’ Law. By comparing the falling speed and the particle size measured from the experiment and data calculated by the equation, we concluded that our result and the experiment are trustworthy.

Using this evaluated method, we measured and report the falling velocity of maize pollen kept in several levels of humidity using about 1.5 mL of maize pollen collected from Canberra 90EX (Takii Seeds) at Kagoshima University Farm.