Researchers found that a special kind of moss only release their spores when their pod structures open up in the dry air helped by wind, which blows the spores out, rather than just opening on its own in humid conditions.

Mosses have long relied on ingenious mechanisms to release their spores into the wind for dispersal and reproduction. Now new research published in AoB PLANTS sheds light on the complex interactions behind spore release in one species with a unique “telescopic” opening structure.

Most mosses employ hygroscopic peristome teeth – structures that open and close in response to humidity – to control the release of spores from capsule-like sporophytes. However, the specific drivers of spore shedding were not well understood in Regmatodon declinatus, a moss with a specialized “telescopic” peristome design. 

Using high-precision measurements, Yanzhi Wu and colleagues tracked the hygroscopic movements of its inner and outer peristome teeth under different conditions. They also counted the number of spores released with and without environmental triggers like wind and moisture. 

Their results revealed several key factors governing spore shedding in this moss. Firstly, they found the outer peristome teeth are significantly shorter than the inner teeth. This triggers the telescopic opening motion where the outer teeth rapidly elongate while closing in on the retracting inner teeth. 

Surprisingly, the hygroscopic opening of the peristome alone released very few spores. It was only when wind was introduced that spore shoot up over 100-fold. Dry capsules also released around seven times more spores than moist ones. 

“When there was no wind, the average number of spores released was 86. Spores were released randomly and sporadically. There was no clear trend. The total number of spores released in the wind was 124 times higher than in the absence of wind.” 

Wu et al. 2023

The team then looked at what might explain the effects of moisture. They proposed dried capsule walls become brittle and more prone to cracking under forces like wind – essentially “helping” spores to escape. By testing this, they discovered that harmed capsules allowed the complete release of the spores. 

By integrating their findings, the researchers proposed a comprehensive “coupled model” culminating in spore liberation in R. declinatus. First, hygroscopic peristome movements initiate opening under dry conditions. Wind then works in tandem to both dislodge clinging spores and potentially crack desiccated capsule walls. Complete spore emission only occurs once all the elements fall into place. 

The study provides new insights into the complex interplay behind cryptic spore dispersal strategies in mosses. It reveals nature employs multiple synergistic mechanisms to maximize reproductive success – even in species with unusual, specialized anatomies. 

READ THE ARTICLE

Wu Y., Wang Z., Zhang Z. (2023) “Telescopic peristomes, hygroscopic movement and the spore release model of Regmatodon declinatus (Leskeaceae Bryophyta)” AoB PLANTS. Available at: https://doi.org/10.1093/aobpla/plad073 

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