Conducting Cells in Mosses

I got an email a while back asking about the leptom and hadrom in mosses (sometimes both of these terms are spelled with an added -e at the end). Admittedly I had not heard these two terms before, but I was pretty sure that they referred to the hydroids (water conducting cells) and leptoids (photoshythate/sugar conducting cells) in mosses. Yes, some bryophytes do have specialized cells for conducting either water or sugars through their plant body, however, the walls of these cells are not strengthened by the compound lignin, so they are not termed xylem and phloem.

I headed to my handy reference shelf to look up the definitions of these two terms and here is what I found about the water conducting cells of mosses.

The hadrom is a term for all the of hydroids together in a structure. In mosses hydroid cells are present in the peristomate mosses (those with teeth around the mouth of the capsule) which includes the Bryopsida, the crown group of mosses, and the Polytrichopsida, the hairy-capped mosses. Hydroids are lacking in some of the earliest diverging lineages: including Sphagnaceae, Andreaeaceae, and Andreaobryaceae.
(Paragraph Updated 16 April 2014:  An earlier version of this post incorrectly stated that hydroids are only present in the Bryopsida. However, in Ligrone et al 2000 they state that hydroids are present in the Bryidae. This older name for the group includes both the Bryopsida and the Polytrichopsida and thus has been updated in the paragraph above.)

The leptom (consisting of leptoids) is unique in mosses to the Dawsoniidae and Polytrichidae (the group of mosses that includes Polytrichum, the hairy capped mosses). Other groups of mosses have cells that could be termed 'conducting parenchyma cells', but they are not as specialized as leptoids. 

These terms (leptom and hadrom) were introduced by the German botanist Haberlandt in 1879, which is probably why I hadn't heard of them before.

If you are interested in reading more, this paper has a very thorough and readable discussion of water conducting cells in bryophytes, which I consulted for the above information on hydroids and leptoids.

R Ligrone, J G Duckett, and K S Renzaglia. 2000. Conducting tissues and phyletic relationships of bryophytes. Philos Trans R Soc Lond B Biol Sci. 355: 795–813. 

To give you a visual of these conducting cells, I remembered that I came across some during the course of my dissertation research. Below is a transverse section through the midrib of a gametophyte leaf of Funaria hygrometrica.

The cells with the thickest walls in the middle-center are stereids, which help to support the leaves. Directly above them are two cells that have a 'blown out' appearance. These cells do not have any cytoplasmic contents and have a very thin wall between them. I would interpret these cells as hydroids. Above and slightly to the right of the hydroids is a large cell with intact cellular contents and a large number of pores in one of the cell walls. Thus I think that this is a food conducting cell or conducting parenchyma cell. 

I have blown up the image and added some letters to help orient you to the larger image above. (Key: stereid = s, hydroid = h, food conducting cell = fcc)

It has been a while since I have looked at and interpreted electron micrographs. Well maybe not so long ago. I did a lot of that for my dissertation but the interpretation stage seems like, and was a couple of years ago. Interpreting this micrograph was super fun and tells me that I need to get back to the electron microscopy lab and generate some more images and data to interpret and think about!

Moss Meetings

Last week I was down in New York at two meetings focusing on Mosses. Yes I go to scientific conferences where everyone is studying bryophytes. Pretty nerdy, I know, but it is actually really fun to hang out with scientists who all share similar interests and to learn about the newest research coming out of laboratories from around the world. 

If you are interested in checking out the talks that were given you can download the brochure with all of the abstracts for each talk given at the meeting. (Abstracts program here) They are basically summaries of the questions asked and major findings of each presentation given at the meeting. They are not nearly as in-depth as listening to the presentation in person, but do give an overview of the topics we covered. 

And here we all are posing outside one of the research buildings at the New York Botanical Garden where the meeting was held.

June 2012 Desktop Calendar

This is an image pulled from my archives. A flashback from 2008. Shown here are some mosses growing in a raked rock garden at a temple in Japan. 

If you are interested in downloading this desktop calendar follow the instructions below. 

1 - Single click on the image to open it up in a new window. (If you use the image directly from the blog post you will loose a lot of resolution.)

2 - Right-click (or ctrl-click) on the image, and chose the option that says, "Set as Desktop Background" or "Use as Desktop Picture". The wording may vary.

3 - If the image does not fit your desktop neatly, you may have to adjust the image (Mac: System Preferences > Desktop > Screen Saver > Desktop; Windows: Control Panel > Display > Desktop) and choose "Fill screen" as the display mode of your background image.

Any issues or suggestions please let me know. These calendars are an experiment in-progress.

Mosses at Trout Brook Valley

I led a moss walk at the end of April at Trout Brook Valley, which is part of the Aspetuck Land Trust in southwestern Connecticut. Unfortunately we had a pretty dry April and the mosses were a little crispy. However, we did locate some that we lush and moist on this drippy rock wall. 

Here we are checking out some mosses growing on a rock. 

Hand-lenses in action!

Thanks to everyone who attended the walk and to Heather Williams Walklet for sending these photos.

The Map of Life. Mapping mosses next?

Have you heard about the Map of Life? They just released their first demo version of the mapping program. The program integrates data on species distributions from a number of sources, such as, point data from collection records, local inventories, and regional checklists. You can either look up a particular species and see where it lives or choose a location in the world and see a list of the species that occur there.   

Thus far they have included Birds, Freshwater fishes, Reptiles, Amphibians, and Mammals. I have suggested to one of my fellow UConn alums, Adam Wilson, who is working on the project, that mosses be added to the mapping list next. Mosses are listed in the Global Biodiversity Inventory Facility (Gbif), so the data is available to add them to this project, but I am guessing that I will have to wait a while until mosses are included. What group would you like to see added to the mapping next? 

Check out the Map of Life program here

Below is an example of the maps that are produced. They use Google Maps and can show multiple layers of distribution data from different sources. The maps are fully interactive and allow you to zoom in to a particular area of interest. I think that this is going to be a really great resource for scientists and amateur naturalists. Imagine going on travels or a collecting trip and being able to pull up a list of all the species in your area, and also a map of previous collection sites so that you can hunt for organisms. (This does assume that you have a fancy phone with web capabilities for the field and that you are not somewhere too remote for a signal.) However, I think that this would be a useful tool prior to heading into the field or for planning a collecting trip.

As an example, this is the distribution map from the smooth earthsnake that I posted about last week.

Some additional information

 - An article from Popular Science talking about the Map of Life.

 - An article in Trends in Ecology & Evolution about the project.

Spore Dispersal by Snakes

I tend to avoid snakes in life in general, but this snake is having a super cool interaction with a moss. If you look closely, it appears that this smooth earthsnake is covered in moss spores!

Close-up of the snake's head.

Close-up of the bright green spores coming out of the moss capsule. 

What do you think? I think that they look like spores on the snake. How long will they stick or how far can the snake go without them falling off? Easy to guess, hard to measure.  Probably a little ways, maybe further depending on how quickly they dry and the cover of plants the snake is crawling through. I think that spore dispersal by animals is a very interesting phenomenon and is under documented in the literature. Have a favorite spore dispersing creature or photos you would like to share?

Thanks to Tobias Landberg, a postdoctoral researcher at Murray State University in Kentucky, for taking and sending me these photos.

Moss Sperm Surviving Desiccation

When I think about moss reproduction, I usually think about the fact that mosses have flagellated sperm that require water to swim to the female archegonium that holds the egg. Researchers at Portland State University have been thinking about sperm survival when desiccated. I think that this is a really interesting question. Imagine that it rains and a moss sperm begins its journey swimming toward and egg. What happens if mid-travel the water dries up and the sperm is stranded? Can the sperm cell survive and resume its journey when it is wet again? 

In this study, the effects of desiccation on sperm cells were examined in three moss species.

Shortlidge, E. E., Rosenstiel, T. N. and Eppley, S. M. 2012. Tolerance to environmental desiccation in moss sperm. New Phytologist 194: 741–750.

They found that a fraction of the sperm were able to survive desiccation (e.g., Ceratodon purpureus, on average 17% survived) and the desiccation tolerance did not vary significantly among species. These results indicate the possibility of a sperm bank existing on the landscape. I have heard about a seed bank and a spore bank, but had not thought about a sperm bank before. I think that this is a pretty cool idea and as the authors mention has significant implications for understanding moss mating systems. That is just one finding from this paper. There is a lot more about desiccation tolerance, the effect of sucrose on sperm survival, and sperm variation. I highly recommend checking out this paper if you are interested in learning more. I think that it is good science and a well-written research article. Kudos to the authors. 

May 2012 Desktop Calendar

Well my hopes for April, when I said I was going to make some time for blog posting, were not realized. Not a single post. Except for the calendar. May will hopefully be better, thought starting off with a calendar post on day 11 is not the best start.

I have decided to blame the lack of April posts on an ongoing case of poison ivy and the delay in the calendar on graduation last weekend. May productivity here I come!

Below, on the calendar, is an unidentified Grimmiaceae from my collecting trip to Kansas and Missouri in March. This little tuft is going to remind me to get things done and to identify him/her by the end of the month. Maybe blog posting on monthly goals is good motivation?

If you are interested in downloading this desktop calendar follow the instructions below.

1 - Single click on the image to open it up in a new window. (If you use the image directly from the blog post you will loose a lot of resolution.)

2 - Right-click (or ctrl-click) on the image, and chose the option that says, "Set as Desktop Background" or "Use as Desktop Picture". The wording may vary.

3 - If the image does not fit your desktop neatly, you may have to adjust the image (Mac: System Preferences > Desktop > Screen Saver > Desktop; Windows: Control Panel > Display > Desktop) and choose "Fill screen" as the display mode of your background image.

Any issues or suggestions please let me know. These calendars are an experiment in-progress.

April 2012 Desktop Calendar

Below is an image of Physcomitrium hookerii from the collecting trip I made to Missouri and Kansas a couple of weeks back. I have some additional photos from my travels to post up. Maybe April will have a little more space for blog posting.

If you are interested in downloading this desktop calendar follow the instructions below.

1 - Single click on the image to open it up in a new window. (If you use the image directly from the blog post you will loose a lot of resolution.)

2 - Right-click (or ctrl-click) on the image, and chose the option that says, "Set as Desktop Background" or "Use as Desktop Picture". The wording may vary.

3 - If the image does not fit your desktop neatly, you may have to adjust the image (Mac: System Preferences > Desktop > Screen Saver > Desktop; Windows: Control Panel > Display > Desktop) and choose "Fill screen" as the display mode of your background image.

Any issues or suggestions please let me know. These calendars are an experiment in-progress.

Naming Species After Scientists?

My former labmate Dr. Juan Carlos Villarreal recently described a new species of hornworts from Columbia.

Villarreal A., Juan Carlos; Campos S., Laura Victoria; Uribe-M., Jaime; Goffinet, Bernard. 2012. Parallel Evolution of Endospory within Hornworts: Nothoceros renzagliensis (Dendrocerotaceae), sp. nov. Systematic Botany 37: 31-37.

Hornworts are a separate lineage of bryophytes that are named for the morphology of the sporophytes. They open by two vertical slits splitting the sporangium into two halves starting at the apex. To the right is an image of several elongated sporophytes sticking out of the frilly gametophyte thallus below. The tallest sporophyte is splitting at the top. However, this is not the new species, but a plant that grew in one of the other cultures that I was growing in the laboratory. 

The new species, Nothoceros renzagliensis is named after Dr. Karen S. Renzaglia, who is a professor at Southern Illinois University. Her research focuses on early land plant anatomy, morphology, and systematics. Juan Carlos completed his master's thesis studying hornworts in her laboratory.

I think that it is fabulous that Juan Carlos named this plant after his former advisor. She is a great scientist who has contributed significantly to the field of bryology. I am completely in favor of naming species in dedication to scientists who have contributed significantly to the study of a particular group of organisms. 

The only time I have been involved in naming a species was for the fern ally Isoetes tennesseensis. This species is endemic to Tennessee, hence the name.

What do you think? Should the specific epithets of scientific names contain information about the region where the organism is found or some other salient morphological feature? Or do you like the idea of naming plants or animals in tribute to great scientists?

March 2012 Desktop Calendar

This is the moss Anacamptodon splachnoides. I just love the sound of that name! You can read more about this species in two earlier posts (Post #1 here & Post #2 here). 

With snow on the ground here in Connecticut hopefully this image will help me last until the green has arrived this spring.
 

If you are interested in downloading this desktop calendar follow the instructions below. 

1 - Single click on the image to open it up in a new window. (If you use the image directly from the blog post you will loose a lot of resolution.)

2 - Right-click (or ctrl-click) on the image, and chose the option that says, "Set as Desktop Background" or "Use as Desktop Picture". The wording may vary.  

3 - If the image does not fit your desktop neatly, you may have to adjust the image (Mac: System Preferences > Desktop > Screen Saver > Desktop; Windows: Control Panel > Display > Desktop) and choose "Fill screen" as the display mode of your background image.

Any issues or suggestions please let me know. These calendars are an experiment in-progress.

Did Mosses Ruin the Planet?

The mosses crept out of the ocean, covering the bare rocks on our desolate planet over 400 million years ago. They sped up the chemical weathering of the rocks and decreased atmospheric carbon dioxide. These nefarious changes triggered glaciation events and a mass marine extinction! Muahahaha...... (yes mosses have an evil laugh) and that is how mosses conquered the land.

A couple of weeks ago, research was published examining the above scenario. The researchers carried out an experiment where they examined the ability of the moss Physcomitrella patens to weather rocks. One of the thoughts was that since mosses do not have true roots they might not alter substrates, such as rocks, in a similar manner. However, they found that the mosses secreted several different organic acids, just like vascular plants. Thus they have the ability to break down and weather rocks. This secretion of organic acids by mosses was not something I had heard about before. Their experiment only examined weathering with and without mosses. But when colonizing land the mosses were not alone. They would have been accompanied by fungi too. The researchers anticipate that the mosses in conjunction with fungal symbionts may even have greater weathering abilities!

Overall I think that it is a really interesting study connecting the colonization of land by mosses to historic patterns of climate change. It shows just how powerful and important plants are for life on our planet! 

Timothy M. Lenton, Michael Crouch, Martin Johnson, Nuno Pires, and Liam Dolan. 2012. First plants cooled the Ordovician. Nature Geoscience 5:86–89.

This post was inspired by a friend who sent me a link to this sarcastic and funny article about this research. I take mild offense to the author calling the mosses names, but otherwise I enjoyed the piece. Thanks Emily!