Phenotypic plasticity in the number of leaf trichomes of Arabidopsis kamchatica subsp. kawasakiana under heavy metal stress

Trichomes, epidermal appendages found on plant surfaces, are known to accumulate zinc (Zn) and cadmium in heavy metal-tolerant plants. This study investigates whether excessive heavy metal stress induces an increase in the number of leaf trichomes in such plants. Utilizing the Zn hyperaccumulator plant Arabidopsis kamchatica subsp. kawasakiana, we conducted field surveys and cultivation experiments to test this hypothesis. The field survey revealed a positive effect of soil Zn levels on the number of trichomes per leaf. Consistently, results from the cultivation experiments demonstrated a significant effect in three out of four ecotypes studied. Our findings suggest that an excess supply of Zn stimulates the formation of leaf trichomes in A. k. subsp. kawasakiana, potentially aiding in physiological stress alleviation. Our results introduce a novel observation of a plastic response, wherein soil Zn levels influence the development of leaf trichomes. The adaptive significance and specific developmental mechanisms underlying this response await further elucidation.