Particulate matter does mechanical harm to plants. Small particles fall on the leaves and reduce light penetration or even block the opening of stomata, thus preventing their proper function. Smaller particles even enter stomata and interact with the biochemistry of plant metabolism this way [4]. Things can get as far as actually preventing the plant from properly photosynthesizing. Plants that are affected by this pollution could lose the most affected leaves or fade due to the inability to photosynthesize.
Source:
https://greentumble.com/effect-of-pollution-on-plants/
