Researchers discover fern capable of independent gametophyte life

New Delhi, Aug 10: A discovery regarding the fern Hymenasplenium murakami-hatanakae has been made, revealing that it can exist as an independent gametophyte, living for extended periods without the need for a spore-producing sporophyte.

This discovery, by the researchers at Tokyo Metropolitan University, was made after the team collected specimens from Izu-Oshima Island in Japan and conducted DNA analysis, which confirmed that this fern, part of the Aspleniineae suborder encompassing 30 per cent of all ferns, belongs to this rare class. The "alternation of generation" is a complex reproductive cycle in plants and algae, involving two distinct phases: the diploid sporophyte and the haploid gametophyte.

In this cycle, gametophytes produce gametes that fuse to create a diploid zygote, which then develops into a sporophyte. Sporophytes, in turn, produce spores that give rise to new gametophytes, thus continuing the cycle. Typically, in land plants, sporophytes and gametophytes are nutritionally dependent on each other.

However, ferns are unique in plant biology because they can exist independently, without the need for the other phase for nutrition. This independence in ferns opens up the fascinating possibility of gametophytes and sporophytes surviving for extended periods in the absence of each other. While most ferns spend the majority of their lives as sporophytes, a few species can exist as independent gametophytes for long periods.

However, due to the rarity of this phenomenon, the life cycle of independent gametophytes remains poorly understood. Professor Noriaki Murakami and his team focused on the Hymenasplenium murakami-hatanakae species, found in the dark, damp, rocky environments of Japan and Taiwan.

Their DNA barcoding technique, which compares DNA from chloroplasts, led to the remarkable discovery that this species' gametophytes could thrive in complete isolation from spores, marking a significant finding for the Aspleniineae suborder.

This discovery challenges the prevailing belief that Aspleniineae ferns spend most of their lives as sporophytes, suggesting that gametophytes can adapt to isolated environments. The researchers hope to further study this species to gain insights into how ferns diversify and adapt to different environmental niches.