Telescopic peristomes, hygroscopic movement and the spore release model of Regmatodon declinatus (Leskeaceae Bryophyta).

Abstract

Moss peristome hygroscopic movement plays an important role in protecting and controlling spore release. Recent studies on the peristome's hygroscopic movement and spore release have focussed on mosses with 'perfect' peristomes, such as Brachytheciaceae, whereas the hygroscopic movement type and spore release pattern of 'specialized' peristomes, such as Regmatodon declinatus, are poorly understood. We investigated the relationship between the peristome's hygroscopic movement and spore release in the 'specialized' peristome of R. declinatus by the measurement of peristome hygroscopic movement parameters and the hygroscopic movement spore release test. It was found that: (i) Exostomes (EX) are significantly shorter than endostomes (EN), triggering the hygroscopic movement of telescopic peristomes, in which the EX rapidly elongate while closing in on the EN, and the teeth rapidly converge. (ii) Spore release was minimal when peristome movement was triggered alone. The number of spores released when exposed to wind was 124 times greater than in the absence of wind. Dry capsules released seven times more spores than wet capsules. The study reveals that the hygroscopic movement of 'telescopic' peristomes of R. declinatus did not contribute significantly to spore release. More spores were released when wind and hygroscopic movement acted synergistically. Dry capsules released the maximum number of spores. It was also revealed that structural damage to capsules can facilitate complete spore release. Finally, we modelled the release of R. declinatus spores from initiation to complete release, namely the coupled release model of wind-water-capsule structural damage.