Tag Archives: mosses

Friday Fellow: Pellucid Four-Tooth Moss

by Piter Kehoma Boll

It’s time to go back to the tiny ones, the mosses. The third species of this group to be featured here is called Tetraphis pellucida or the pellucid four-tooth moss. Found in the northern hemisphere, this species is common in deciduous forests and grows almost exclusively on decaying wood of coniferous trees.


The general appearance of the pellucid four-tooth moss on a decaying log. Photo by Hermann Schachner.*

The pellucid four-tooth moss can have two different modes of reproduction: sexual and asexual. The sexual reproduction occurs in a way similar to that found in most mosses. The asexual one, however, is somewhat peculiar and happens through the production of propagules called gammae. Gemmae can occur along a stalk, being called stalk gemmae, or inside a cup formed by three to five large leaves, a structure called gemmae cup. Gemmae from both stalks and cups are propelled by the power of raindrops. What is interesting is that the type of gemmae structure seems to be related to the inclination of the surface in which the moss grows. From a horizontal surface to one with an inclination of about 18°, cups are more common, possibly because a water drops falling inside a cup propels the gemmae with great speed upward. On surfaces with inclinations above 18°, stalks are more common, as a cup lying on its side wouldn’t be very useful, and water can wash down gemmae from stalks more easily.


A closer look showing several gemmae cups. Photo by Hermann Schachner.

Regarding dispersal, spores from sexual reproduction seem to be able to move farther away from the mother, but they are not as successful in germinating and occupying a new substract as gemmae. Thus, the different reproduction modes seem to help this amazing little moss to spread by adapting to the most adequate means.

However, when other moss species arrive at the substrate, the pellucid four-tooth moss is rapidly replaced. It has, therefore, a very low success when competing with other species. How can it be one of the most common species in its habitat then? Well, it is so because the specialized propagules of the pellucid four-tooth moth allow it to quickly colonize newly-formed substrates, which arise from the common disturbances on the forest floor. No other species can colonize that quickly, but as they can easily dislodge our fellow, there is an endless struggle to survive. The pellucid four-tooth moss relies on disturbance to go on.

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Kimmerer, R. W. (1991) Reproductive ecology of Tetraphis pellucida. I. Population density and reproductive mode. The Bryologist 94(3): 255-260. https://doi.org/10.2307/3243962

Kimmerer, R. W. (1991) Reproductive ecology of Tetraphis pellucida. II. Differential Success of Sexual and Asexual Propagules. The Bryologist 94(3): 284–288. https://doi.org/10.2307/3243966

Kimmerer, R. W. (1993) Disturbance and dominance in Tetraphis pellucida: a model of disturbance frequency and reproductive mode. The Bryologist 96(1): 73-79. https://doi.org/10.2307/3243322


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Filed under Botany, Friday Fellow

Friday Fellow: Spreading Earthmoss

by Piter Kehoma Boll

If you still think mosses are uninteresting lifeforms, perhaps you will change your mind after knowing the spreading earthmoss, Physcomitrella patens.

Found in temperate regions of the world, except for South America, but more commonly recorded in North America and Eurasia, the spreading earthmoss grows near water bodies, being one of the first species to colonize the exposed soil around pools of water. Although widely distributed, it is not a common species.


The spreading earthmoss growing on mud. Photo by Hermann Schachner.

Since the beginning of the 1970s, the spreading earthmoss has been used as a model organism, especially regarding gene manipulation. Differently from what occurs in vascular plants, the dominant life phase in mosses is the gametophyte, an haploid organism, meaning it has only one copy of each chromosome in its cells. This is an ideal condition for the study of gene expression, as the activation or inactivation of a gene is not hindered by a second one in another copy of the chromosome in the same cell.


Physcomitrella patens growing in the lab. Credits to the Lab of Ralf Reski.*

By controlling gene expression in the spreading earthmoss, researches can track the role of each one of them in the plant’s development. Comparing these data with that known from flowering plants, we can have a better understanding of how the plant kingdom evolved.

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Cove, D. (2005). The Moss Physcomitrella patens Annual Review of Genetics, 39 (1), 339-358 DOI: 10.1146/annurev.genet.39.073003.110214

Schaefer, D. (2001). The Moss Physcomitrella patens, Now and Then PLANT PHYSIOLOGY, 127 (4), 1430-1438 DOI: 10.1104/pp.127.4.1430

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Filed under Botany, Friday Fellow, Molecular Biology