The Physical Effects of Dust on Photosynthetic Rate of Plant Leaves

Abstract

Dust cover on leaves is considered to affect photosynthesis directly, mainly by shading leaf surface, increasing leaf temperature and plugging stomata. This study was carried out to make clear these physical effects of dust on photosynthesis. Four classes of JIS Z 8901 dust (Carbon-Black and Kanto-loam powder Coarse, Fine, Ultrafine), which were different in particle size and had pH values around neutrality, were applied to upper surfaces of leaves of kidney bean and cucumber plants at various densities. These two species were different in stomatal density. Both net photosynthetic rates and leaf temperatures of dusted leaves and clean leaves were measured at the same time, over a range of light intensities.
The following results were obtained both in kidney bean and cucumber plants.
(1) Photosynthetic rate was reduced by dust. As dust density on leaf surface increased, it was reduced further.
(2) When carbon-black was applied, leaf temperature increased by 3°C at the maximum, but none of three classes of kanto-loam powder increased leaf temperature.
(3) Regardless of dust characteristics or dust density, the reduction in photosynthetic rate was nearly equal to the reduction in PPFD incoming to upper surface of leaf by dust accumulation, in all measurments in this study.
Therefore it seemed that the shading leaf surface was the most important of the injurious physical effects of dust on photosynthesis.