Field of Science

Berry Go Round #48

Welcome to the January 2012 edition of Berry Go Round!  Here are some interesting botanical posts that I found from the past month. Enjoy!

- Have you heard about the plants that eat nematodes? If not, head over to Cunabulum to read all about the genus Philcoxia and the research into these carnivorous plants.

- For those that love botanical history, here is the tale of Aven Nelson and the Laramie columbine at In the Company of Plants and Rocks. The photos of the Wyoming landscape have me thinking about traveling out west. The discussion of naming different granite types is a vignette that all taxonomists can enjoy.

- This month the U.S. Department of Agriculture (USDA) published a new Plant Hardiness Zone Map for 2012. The release of this new map was mentioned on quite a number of gardening blogs. I found the discussion at Greg Laden's Blog to be the most interesting. The comments center on how this revised map may influence thinking surrounding climate change.

- There is a super cool story about solar-powered sea slugs at Postdoc Exploring. These slugs are feeding on the chloroplasts from algae, incorporating them into their cells, and then using them to photosynthesize. There are several videos to watch. In one, you can see the slug slurping the chloroplasts from inside the algae, like drinking through a straw.

- This is a blog that is totally new to me. It is called Phytography. A botanical word of the day is explained through amazing photos of plants from New Zealand. I am especially partial to furrow on Jan 1st and spiral on Jan 26th. Which one is your favorite?   

- I am still longing for a real vacation, since finishing up my PhD in December and have been imaging an escape to points south over spring break. Maybe I will head to South Carolina. Anybody Seen My Focus? has two posts (evening and morning) highlighting a winter trip to the Savannah National Wildlife Refuge in South Carolina. Some of the grasses are a little brown this time of the year, but overall there is way more green than we have here in Connecticut and it looks like a nice place to visit. I am imagining water, hiking, plants, and being far away from my computer. Any other suggestions?

- Thinking of painting your house in 2012? How about covering it in plants instead? Seeds Aside has some lovely photos of a museum in Paris that is covered in an abundance of plant life. 

- The Phytophactor discusses the invention of dichotomous keys and a recent article that highlights an image-based key that predates text-based dichotomous keys by 100 years. You can check out scans of the original drawings used in this image-based key here at the Royal Society.

Stay tuned for February's Berry Go Round hosted at A Blog Around The Clock.

Growing on Trees in Acadia National Park

My first volume of the journal Bryologist for 2012 has arrived. Thus, I am trying to finish up my reading of articles from 2011. The last one I had to read looked at the interaction between the rain/fog chemistry, the type of tree, and the lichens and bryophytes living on the trees.

I have been asked several times about whether there are different types of bryophytes that grow on different types of trees. This study really got me thinking about the importance of substrates for bryophytes and lichens. 

Some of their findings...
- Sites with less acidic fog have higher epiphyte biomass.
- Spruce bark is generally more acidic (lower pH) than maple bark. 
(This is not something new but definitely something I want to keep in mind when talking to people about the pH of the bark of different species of trees.) 
- Fog sulfate content and bark pH were good predictors of macro-lichen composition.
vary along the length of a single trunk.

Overall it was a really cool study and I would highly recommend it if you are interested in thinking about the influence of polluted rain/fog on both lichens and bryophytes.

Is the plural Calyptrae or Calyptras?

The moss calyptra is a small cap of gametophyte tissue that covers the apex of the moss sporophyte during its development. This little structure was the focus of my dissertation. Below is part of a figure that I used in my defense showing calyptra from several different moss species. The calyptrae are indicated by the orange arrows

This discussion may seem (ok) is pretty esoteric, but a reviewer on my last manuscript brought up this question. They proposed using calyptras as the plural of calyptra, rather than calyptrae. (Yes, these are the things that I think about for my job.)

This is part of the reviewer response that I sent to the editors regarding this question.
We agree that there are challenges when adopting terms into other languages especially concerning the plural form of the word. The term calyptra is derived from the Greek word kalyptra, meaning veil or hood. The plural for the Greek word kalyptra is kalyptrai. However, with the change in spelling and its use in other languages the term has been latinized. Often Greek plurals ending in –ai are transformed into –ae (e.g., mycorrhizae, cypselae, thecae). Perhaps this was originally a spelling error, but at least in terms of the moss calyptra the –ae ending has persisted. In the two most widely used bryological glossaries (see references below) the plural form is cited as calyptrae and many papers and books use this plural form. I do not think that retaining this traditionally used plural form makes the study any less accessible to non-bryologists as there are other botanical terms that have similar plural forms. Thus, we would prefer to continue to use calyptrae as the plural form in our manuscript. Additionally, switching to an –s ending would require additional explanation, which is outside of the manuscript’s focus.
Thanks to my colleague Nic Tippery who contributed to this explanation and I consult on all words Greek and Latin.

The Tree Moss Climacium

This is a really cool moss that often grows in seepy, shady areas next to standing pools of water or streams. It's common name, tree moss, comes from the growth form of its leafy gametophyte, which resembling a tiny tree. Due to its tree-like appearance these plants have been used as the trees in model train displays. I have also heard that they were used as decorations in ladies hats.
Shown here is the species Climacium dendroides. I took some photos and wanted to share them because this is the first time that I have seen this species with sporophytes, and thus the first time that I have seen their calyptrae.

The calyptra (shown on the left) is pale yellow, smooth, and cucullate (splitting up a single side upon capsule expansion). I wanted to section some of them to look at their cuticle, but I lost this one. Then when I went back to the population that was collected for DNA extraction in the lab I found that all the calyptrae and sporophytes had already been used for a massive DNA extraction. Too bad. It would have been cool to get a look at their calyptrae using the electron microscope. 

A really spectacular feature of the sporophytes are their peristome teeth! The exostome (outer ring of teeth) are deep brown-red in color. They contrast well with the endostome (inner ring of segments) that are golden brown. The inner teeth are longer and when dry the outer teeth curve inward, as shown in the image below.

The genus name Climacium, comes from the Greek word klimax, which means ladder. The researchers who named this genus thought that the endostome had the appearance of a ladder. I think that it is a pretty accurate description. However, one would have to be tardigrade-sized to use them as a ladder!

Keep an eye peeled for this species if you are in deciduous forests that have some wet areas. I see the gametophytes regularly in Connecticut and seeing some sporophytes is definitely a treat!


Mosses without Sex for 50,000 years

Karlin, E. F., Hotchkiss, S. C., Boles, S. B., Stenøien, H. K., Hassel, K., Flatberg, K. I. and Shaw, A. J. (2011), High genetic diversity in a remote island population system: sans sex. New Phytologist

This is a super cool article! The research was reported on both at National Geographic Daily News and Science Daily. I decided not to write my own summary of the research, since these two articles do such a good job. Check out these two sites for highlights of the research, which also includes an interview with the lead author. Scientific communication in action!  

A Great Start to the New Year!

2012 has started out super well for me professionally. The second chapter of my dissertation was just published!

The short summary is that the calyptra is a little cap of female gametophyte tissue that covers the moss sporophyte apex during development. If it is removed from the apex early during development the sporophyte apex dries out and the sporophyte may die. I confirmed a long-proposed idea that the calyptra is covered by a waxy cuticle. I found that the calyptra cuticle is significantly thicker than the cuticle on either the leafy gametophyte or sporophyte. These anatomical differences may point to a functional role of the calyptra cuticle in desiccation protection of the underlying sporophyte.

This paper is the next part of that story. The calyptra cuticle develops when the calyptra is quite small and completely surrounds the sporophyte embryo. Even at this early stage of development, the calyptra cuticle is multilayered and thick. At this stage the moss sporophyte cuticle consists of a single thin cuticle layer. The sporophyte cuticle develops as a wave from the bottom up, adding layers and thickening across the nine developmental stages I examined. 

I think that this figure ended up being a good summary of the development of the cuticle layers.

Figure 7. (From the AJB paper)
Diagram illustrating cuticle layers on the calyptra and sporophyte for stages 1 to 9 (Table 1), with numbers of the developmental stages identified beneath each diagram. The calyptra is covered by a multilayered cuticle at all nine developmental stages. Numbers inside the sporophytes indicate the different number of cuticle layers present at each region of each developmental stage. Abbreviations: C, calyptra; CL, cuticular layer; CWP, cell wall projections of the cuticular layer; eDCP, electron-dense cuticle proper; eLCP, electron-lucent cuticle proper; S, sporophyte.

The idea is that the calyptra has a complex cuticle even at early developmental stages. This early cuticle development may enable the calyptra to protect the young sporophyte from drying out. During early development the sporophyte cuticle is less complex and thus the sporophyte may require protection. Later in development, the moss sporophyte develops its own cuticle and the protection of the calyptra may no longer be necessary.

Overall, I think that my studies are adding to the scientific evidence that points to the importance of the calyptra for the development of the moss sporophyte. Stay tuned for the final chapter where I experimentally removed the calyptra cuticle to get at its importance for sporophyte development and fitness. Happy New Year!

The formal abstract for the paper is below.

Premise of the study: In vascular plants, leaf primordia prevent desiccation of the shoot apical meristem. Lacking leaves, the undifferentiated moss sporophyte apex is covered by the calyptra, a cap of maternal gametophyte tissue that is hypothesized to function in desiccation protection. Herein, we compare cuticle development on the calyptra and sporophyte to assess the calyptra’s potential to protect the sporophyte from desiccation. As the first comprehensive study of moss sporophyte cuticle development, this research broadens our perspectives on cuticle development and evolution across embryophytes.
Methods: Calyptrae and sporophytes at nine developmental stages were collected from a laboratory-grown population of the moss Funaria hygrometrica. Tissues were embedded, sectioned, then examined using transmission electron microscopy. Epidermal cells were measured for thickness of the cuticle layers, cell wall thickness, and lumen size.
Key results: The calyptra cuticle develops precociously and reaches maturity before the sporophyte cuticle. Calyptrae are covered by a four-layered cuticle at all stages, whereas sporophyte cuticle maturation is delayed until sporangium formation. The development and thickening of the sporophyte cuticle occurs in an acropetal wave.
Conclusions: A multilayered calyptra cuticle at the earliest developmental stages is consistent with its ability to protect the immature sporophyte from desiccation. Young sporophytes lack a complex cuticle and thus may require protection, whereas in older sporophytes a mature cuticle develops. The moss calyptra is not a vestigial structure, but rather the calyptra’s role in preventing desiccation offers a functional explanation for calyptra retention during the 450 Myr of moss evolution.