Parent Child Relationships continued...

The calyptra is a cap of maternal gametophyte tissue that covers the apex of the offspring sporophyte during development. My research shows that in the calyptra has a waxy cuticle that develops early and prevents water loss from the underlying sporophyte tissues. I think about this as the maternal gametophyte investing in these protective layers to keep the sporophyte safe from the harsh conditions of drying out as it grows taller and taller. 

This figure illustrates the maternal gametophyte calyptra
and its location across the stages of sporophyte development. 

An additional interpretation is presented by Haig. He views the waxy layers on the calyptra as slowing down or preventing the sporophyte from pulling up more water and potentially nutrients from the maternal plant. 

 Haig, D. (2012). Filial mistletoes: the functional morphology of moss sporophytes Annals of Botany, 111 (3), 337-345 DOI: 10.1093/aob/mcs295

These differing interpretations of the same phenomenon are not mutually exclusive. One is not right and the other is wrong. As Haig mentions, both maternal protection and restraint are likely to be occurring at the same time. This relationship between mothers and their offspring is a phenomenon that is seen across the plant and animal kingdoms.

Parent Child Relationships

Relationships between parents and children are complicated. This is not only true for people and animals, but it is also true for plants. In this research paper Dr. David Haig explores the relationship between mothers and their offspring in mosses.

 Haig, D. (2012). Filial mistletoes: the functional morphology of moss sporophytes Annals of Botany, 111 (3), 337-345 DOI: 10.1093/aob/mcs295

This is a figure that I am working on for 
a paper that I am writing. It is still a work
in progress. If you have any comments or
suggestions for improvement feel free to
leave them at the end of the post.

In mosses the maternal gametophyte plant and the offspring sporophyte have a lifelong relationship. The offspring remain attached to and nutritionally dependent on the maternal plant throughout its lifespan, so nutrition is a major component of their relationship. These shared resources cause a conflict. The maternal plant needs to provide enough nutrients and water to the developing offspring for it to grow and mature, however, if the offspring takes too much the maternal plant may die. The offspring, on the other hand, is out to maximize its growth, despite any negative effects to the maternal plant. Haig goes into a more detailed discussion of the genetics behind this conflict, but what particularly interests me are his interpretations of moss structures and their functions in light of this conflict.

Stomata are cells with an opening between them. These pores enable gas to enter the leaves for photosynthesis in many plants. Additionally water escapes from the plant through these pores, drawing up water from the roots to the leaves. Haig's interpretation for mosses is that the stomata in the capsule are helping the sporophyte offspring to pull water and nutrients from the maternal gametophyte at higher rates. Thus increasing the resources that it is able to acquire. Often the photosynthesis explantation for moss stomata function is invoked, but I think that this is a really good alternative hypothesis for the stomata on moss sporophytes. As Haig so aptly said, "Sporophytes suck."

He also interprets the moss calyptra in light of this struggle between offspring and maternal plant. I am running a little late for game night, so the rest of this discussion is to be continued... 

Everyone wants to be called a Moss

There are plants that we call mosses that are not really mosses. Spanish moss (in the pineapple family), clubmosses (a fern friend), and carrageen moss (a red alga that is used in foods as a thickening agent). I like to call them mossy misnomers. Their common names include the term moss, but really they are not bryophytes nor do they look much like them. However, this stick insect is worthy of his mossy moniker. It is camouflaged to look like a moss and is doing an amazing job!

Trychopeplus laciniatus - Moss mimic stick insect
Photo by dandoucette on Project Noah

Crawling along on a moss covered tree the frills blend in with the surrounding moss making it hard for predators to spot this stick insect. Check out some of the great photos posted on Project Noah for this insect and many others. Thanks to my labmate Ciera Martinez for sending me this photo!     

Trychopeplus laciniatus on a moss-covered tree
Photo by dandoucette on Project Noah

The Zombie Mosses Rise from Beneath a Glacier

Mosses that were buried beneath a glacier for the last 400 years were able to resume growth. Fortunately these resurrected mosses will not be out to eat us. These findings were reported last week in the journal The Proceedings of the National Academy of Sciences by a Canadian research group led by Dr. Catherine La Farge. (As a side note we are academically related, she and my PhD advisor Dr. Bernard Goffinet were both graduate students of Dr. Dale Vitt. Does that make her my academic Aunt?)

La Farge, C., Williams, K., & England, J. (2013). Regeneration of Little Ice Age bryophytes emerging from a polar glacier with implications of totipotency in extreme environments Proceedings of the National Academy of Sciences DOI: 10.1073/pnas.1304199110



This is an amazing story of the ability of mosses to survive freezing in extreme environments. It is well-known that the leafy gametophytes and even the sporophytes of some mosses can survive the winter beneath the snow pack. These findings push our thinking about how long mosses can survive frozen far beyond what they have been shown to previously tolerate. That means that cryopreservation of mosses for 100s of years is not a farfetched idea for some species!

Figure 5b from La Farge et al 2013
Showing a region of new moss growth growing
from plants frozen since the last Little Ice Age (LIA). 

The authors bring up a number of interesting aspects to the research. Particularly I think that it really changes how I think about the colonization of plants in exposed areas post-glaciation. Not all of the plants may need to arrive from afar or recolonize from glacial refugia. Some of the bryophytes may just regrow from frozen but not dead plants.   

Figure 6c from La Farge et al 2013
Showing a petri dish full of mosses regenerated
from frozen plants.  

If you are interested in reading more about the findings and hearing an interview with Dr. La Farge check out the following pieces. (There are many more online. These are just a few of the ones that I read and liked.)

Audio Reports

30 Second Science - A very short piece summarizing the major findings. 

NPR Talk of the Nation Science Friday - An approximately 12 min long interview with the lead author.


Written Articles

The Edmonton Journal - 400-year-old frozen moss brought back to life in scientist’s lab

Science-News.com  - Biologists Revive 400-Year-Old Plants

BBC - Centuries-old frozen plants revived

Discovery News - Zombie Plants Return from the Dead

CBC - Includes an interesting thought about sending bryophytes to Mars.

June 2013 Desktop Calendar

I spent the past week visiting my family in Cincinnati, Ohio. We went for a ride on an old railroad bed that was converted into a bike path. This Fissidens was growing on a muddy bank at the edge of the woods. It was a nice day for a ride a little muggy, but pleasant with the bike-generated breeze. Now back to the dry heat of central California and my mosses in the laboratory.

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 lose 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 and Screen Saver - Desktop; Windows: Control Panel - Display - Desktop) and choose "Fill screen" as the display mode of your background image.

An Ecotourism Vacation

The end of the school year has me thinking about summer vacations and I have just added a new location to my vacation wish list. The Cape Horn region of southern Chile and Argentina sounds like an amazing place to visit! The area has high levels of bryophyte diversity and a beautiful landscape of waterways and islands. Unfortunately my summer vacation plans do not include the Cape Horn this year. Instead I have been reading a book all about ecotourism of the miniature forests and imagining myself there. 

Miniature Forests of Cape Horn: Ecotourism with a Hand Lens (2012) by Bernard Goffinet, Ricardo Rozzi, Lily Lewis, William Buck, and Francisca Massardo.

This book makes it easy to imagine you are far away in the Cape Horn. There are many full color photos of the landscape and a up close photos of the plants. They also identify the many species of mosses, liverworts, hornworts, and lichen that live in the Cape Horn region. The book has text in both English and Spanish, as you can tell from the cover. 

For some of the species they describe interesting structures, such as the lamellae on the leaves of the Polytrichaceae.

For others, cool interactions, such as the flies that are attracted to moss capsules and disperse the sticky spores are featured.

Overall I think that it is a great book. I may be a little biased since I know two of the authors quite well (Goffinet was my PhD advisor and Lewis was my labmate at the University of Connecticut). I think that the book is a great outreach tool and I hope that many people will take them up on visiting the area to see the amazing miniature plants. 

May 2013 Desktop Calendar

I think that this moss covered rock looks a lot like a large turtle shell, or maybe a tortoise. It was about the size of the hood of a small car, so a lot larger than a turtle, but you get the idea.

This month's calendar was also taken at the top of the ridge in the Stebbins Cold Canyon Reserve. I wanted to be sure that I got the calendar prepped and posted before the start of the month. The las couple of months ran a little late.  

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 lose 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 and Screen Saver - Desktop; Windows: Control Panel - Display - Desktop) and choose "Fill screen" as the display mode of your background image.

Mosses in the Arctic

When you think about the arctic what do you imagine? Things that come to mind for me are northern Canada, Siberia, flat, cold, caribou, reindeer, polar bears, and mosses. Yes, there are a lot of mosses that live in the arctic. Not many plants grow that far north, but mosses can handle the extremes. They are tough. There are not many different species of mosses in the arctic, but a significant bulk of the plant life (biomass) is mosses.

This study examines how much mosses contribute to the ecosystem by storing carbon in their plant bodies (biomass). They found that the mosses contributed 25% of the gross primary productivity (above and below ground growth) in the arctic ecosystem that they examined. This is a significant contribution to the ecosystem carbon cycle! Hence one of the authors' final conclusions is that mosses need to be included in vegetation carbon models in order to have an accurate picture of the carbon cycling. 

I think that this is a really important take-home message. Especially in far northern ecosystems, mosses make up a large portion of the plant life. If we are to understand and plan for the effects of global climate change on these far northern places, we cannot ignore the mosses. 

Street LE, Subke JA, Sommerkorn M, Sloan V, Ducrotoy H, Phoenix GK, Williams M (2013). The role of mosses in carbon uptake and partitioning in arctic vegetation. The New phytologist PMID: 23614757

Sphagnum mosses (aka. peat mosses, pictured below) were one of the focal species of their study.

Photosynthesis in Hornworts

Photosynthesis is the most important biological reaction on the planet. It creates the sugars and starches that we and other animals rely upon for food. Photosynthesis also helps to regulate the climate by binding up carbon from the air to keep the planet cooler. Plants need carbon dioxide, water, and light to carry out photosynthesis. 

Hornworts have a cool structure called a pyrenoid that helps to increase the rate of photosynthesis in these plants. Pyrenoids increase the concentration of carbon dioxide close to the enzyme RuBisCO, which is critical for photosynthesis. A recent study examined pyrenoid evolution in the hornworts, the bryophyte lineage most closely related to flowering plants. They asked whether the evolution of the pyrenoid in hornworts was correlated with historically low levels of carbon dioxide in the atmosphere. It is predicted that low levels of carbon dioxide in the atmosphere would put pressure on plants to evolve mechanisms that enable them to increase the concentration of carbon dioxide in their cells in order to increase rates of photosynthesis. 



Villarreal, J. & Renner, S. (2012). Hornwort pyrenoids, carbon-concentrating structures, evolved and were lost at least five times during the last 100 million years Proceedings of the National Academy of Sciences, 109 (46), 18873-18878 DOI: 10.1073/pnas.1213498109

Their results support the pyrenoid structure evolving 5 or 6 times across the hornworts (transition from blue to red in the figure below). Pyrenoid evolution does not appear to be synchronous, each time the pyrenoid evolved across the tree was at a different time in the past. If they had evolved in response to changes in the atmosphere, we would predict that they evolved at the same time. They also did not find a relationship between low atmospheric levels of carbon dioxide and pyrenoid evolution. Even when atmospheric carbon dioxide levels were low, new hornwort species evolved that did not have a pyrenoid. If the pyrenoid was really advantageous, we would predict that when the carbon dioxide levels were low only species with a pyrenoid would evolve new species. Based on this and other findings, they propose that the evolution of the pyrenoid may be related to something other than the atmospheric concentration of carbon dioxide

Figure 1 from Villarreal & Renner 2012. This shows the relationships
between different species of hornworts. The species in blue do not have pyrenoids
and the species in red do have pyrenoids. The black and white inset images show the
different types of pyrenoids found in hornwort species. 

Who is your favorite scientist?

One of my favorite scientists is Dr. Katherine Esau. I think that her book Anatomy of Seed Plants is an invaluable resource for anyone interested in the structure of plants. It is just too bad that the text doesn't cover bryophytes and ferns. I would love to read her interpretations and thoughts for teaching students about bryophyte structures. We have tried using other textbooks to teach a university level plant anatomy course, such as Introduction to Plant Structure and Development, but ended up returning to Esau's text. The text is a little dated (the second edition came out in 1977), but only in the sense that it does not include the most recent literature and thus lacks a molecular perspective. (Books on plant structure and development that connect to gene function, which I like, include The Molecular Organography of Plants and Mechanisms in Plant Development.) Recently a 3rd edition of Esau's Anatomy of Seed Plants has been updated by Ray Evert. This version is a nice addition, but in my opinion is much more a reference book for your shelf than a text to be used for teaching. I think that Esau's Anatomy of Seed Plants is the best text to teach students the basics of interpreting plant structures.

Dr. Esau in 1958. Image from the collection of UC Santa Barbara,
Cheadle Center for Biodiversity and Ecological Restoration

Dr. Esau's early life was full of twists and turns. Her family fled Czarist Russia to Berlin in 1918/1919. Then she immigrated to the United States in 1922 and continued her studies out in California. A couple of nice articles have been written that summarize her life story. One is published in the Plant Science Bulletin and the other is in The Botanical Review.

Her research focused on the development and structure of plant phloem. Phloem are the cells that move sugars around inside the plant body. One of her major research tools was the electron microscope, pictured below. I think that electron microscopes are a lot of fun to use. It is amazing how far you can zoom in and all the cellular details that you can see! 

Dr. Esau working at the microscope.
Image from the collection of UC Santa Barbara,
Cheadle Center for Biodiversity and Ecological Restoration

I was inspired to write this post by the blog Dead Scientist of the Week. 

April 2013 Desktop Calendar

I went for a hike this weekend at the Stebbins Cold Canyon Reserve. It was a really great hike up into the Coast Range with some great views of the mountains and beyond! We saw some nice mosses like this small Fissidens and the spring wildflowers were in bloom.

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 lose 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 and Screen Saver - Desktop; Windows: Control Panel - Display - Desktop) and choose "Fill screen" as the display mode of your background image.

This is the view back into the mountains.

And this is looking over the ridge out into the central valley. We could see the towns of Winters and Davis, and then way off in the distance is the skyline of Sacramento. 

I would definitely recommend this hike to anyone in the area. Great views from ~1500 feet up and a lot of great plants to check out!

Berry Go Round - March 2013

The newest edition of the plant carnival Berry Go Round is up at the blog In the Company of Plants and Rocks.  There are some good plant posts in the line up that you should definitely check out. 

The photos from Geotripper of spring wildflowers of the Sierra Nevada foothills are getting me excited about going hiking this upcoming weekend. We had a good amount of rain this week and I am looking forward to seeing some spring bryophytes in addition to the showy wildflowers. 

I would also recommend checking out the post on bees, flowers, caffeine, and memory at SciLogs. I think it is a really interesting study and those of you who love coffee and the effects of caffeine will find this study quite interesting.

Those are just a couple of highlights from the carnival. Head to In the Company of Plants and Rocks for the full carnival experience. For more about blog carnivals and my posts about the earlier editions of Berry Go Round, click here.