Most studies of metal-tolerant ferns focus on the leafy sporophyte, the stage we normally recognise as the plant. Kamachi et al. (2005) asked whether lead tolerance in Athyrium yokoscense is already present in the haploid gametophyte, the small, heart-shaped stage that produces gametes.
A fern with broad metal tolerance
Athyrium yokoscense is already known as a cadmium hyperaccumulator and as a fern that tolerates copper, zinc, and lead on contaminated soils in Japan. Lead concentrations in sporophyte fronds have been reported in the 1,000–10,000 µg g⁻¹ dry-weight range, depending on substrate. That broad tolerance makes it a useful counter-example to the idea that metal handling is highly element-specific.
Gametophyte tolerance
The researchers germinated spores on media containing elevated lead and found that A. yokoscense gametophytes survived and accumulated lead at concentrations that inhibited other fern species such as Pteridium aquilinum and Pteris vittata. The gametophytes also showed lead accumulation in tissues, indicating that the protective and transport machinery is active well before the sporophyte develops.
Implications for propagation and biogeography
If tolerance is gametophyte-expressed, then populations can establish on contaminated substrates from spores without needing a pre-adapted sporophyte generation. That trait matters for colonisation of mine wastes and for ex-situ propagation: spore banks could theoretically be used to establish remediation stands on lead-rich sites.
This analysis is grounded in the cited primary source. See our methodology for how multi-metal records are verified.