Field of Science

Preview of the Book "Nesting Season" at Northern Woodlands Magazine

A few of the nests featured in this article appear to include mosses as part of their construction materials. At least that's what it looks like from the photos and drawings.
I wonder how many different species of birds use mosses to build their nests?

Moss Cell Walls Like Sponges

I came across this paper when cleaning off my computer desktop today. My labmate Juan Carlos sent it to me a while back. Upon stumbling across it again I decided to give it another read.

H. G. Edelmann, C. Neinhuis, M. Jarvis, B. Evans, E. Fischer and W. Barthlott. 1998. Ultrastructure and chemistry of the cell wall of the moss Rhacocarpus purpurascens (Rhacocarpaceae): a puzzling architecture among plants. Planta 206:315-321.

This paper focuses on the unique cell walls of leafy gametophyte of this moss. (For a little review of plant cell walls check out last week's post.) Rhacocarpus purpurascens grows in the high mountains of some tropical areas. It grows in large sheets that hang from rock faces and they pick up most of their water from fog. It has been known since the 1970's that the cell walls of this plant are structurally sponge-like. (Think your morning english muffin with a lot of nooks and crannies.) Typical plant cell walls are solid. This study sets out to analyze the walls using a number of methods.

They use some high-tech techniques such as electron microscopy (scanning and transmission), nuclear magnetic resonance (NMR) spectroscopy, and cell wall fractionation. Fancy techniques such as these are great. I use both types of electron microscopy in my own research. However I also enjoy techniques that have an elegant simplicity, which is how I would describe the two other experimental methods that they use (external water conduction and water-holding capacity). Basically these methods allow the authors to ask two questions: Can these sponge-like cell walls conduct water up the moss plant? and How absorptive are these cell walls? In these two experiments they compared Rhacocarpus purpurascens to two or three other moss species that have solid cell walls.

For external water conduction the placed the bottom end of the moss stem into a tube of water and measured how far up the stem the water traveled. They found that the water did not move very far up the stem in Rhacocarpus purpurascens, whereas the other species became hydrated all the way to the tip. Thus the cell walls are not functioning in water conduction.

For water holding capacity plants were dried, soaked in water for 10 minutes and then weighed. Contrary to what you might have anticipated, Rhacocarpus purpurascens held 25% less water than the other species per gram of dry weight. (So it does not appear to be acting as a sponge, which was my initial thought when reading the paper.) However a majority of the water that this plant has access to is in the form of fog. It is not submerged when growing in its native habitat. The authors anticipate that the wall characteristics allow the available moisture to be absorbed quickly and moved inside the cell.

I think that it is pretty cool when scientific questions can be asked and answered using simple techniques. It just goes to show that scientific experimentation is accessible to more than university researchers.

Latest Moss Gardening Book

I'd like to introduce you to my latest book purchase. Native Ferns, Moss, and Grasses: From Emerald Carpet to Amber Wave, Serene and Sensuous Plants for the Garden by William Cullina of the New England Wild Flower Society.

If you are interested in gardening with mosses I think that this book would be a great addition to your bookshelf. A limited preview edition is also available through GoogleBooks. The suggestions that he gives are highly detailed including sections on: Choosing a Site, Site Preparation, Transplanting Moss, Blending Moss, Establishing Moss on Rocks, and Maintenance. I found his explanations clear and his text easy to read. I think that he covers all the steps needed to successfully maintain a moss garden. I was a little disappointed that only 13 moss species are covered. The book is heavier on the fern and grasses. The mosses that are included are rated from easy to difficult in terms of their ease to grow, which will help to point you in the right direction depending on your moss gardening skill.

I am happy to report that I am not lodging my biggest complaint about moss gardening books when it comes to this text. Often they skip over discussions of conservation, wild-collection vs. greenhouse grown, and sustainable harvesting. Not this book. These environmentally conscious threads are woven throughout the text. The author works for a top notch conservation group, so I guess his including these topics is not too surprising. It is just one of the things that I look for when reading and evaluating gardening books. Happy reading!

Moss Protonema and Lead

This week in Bryology Lab group I presented a scientific journal article about lead and mosses. It was a pretty interesting read. You may know that some heavy metals (ex. lead and mercury) are toxic. Think kids eating contaminated lead paint. It is bad for them and will make them sick. Well plants are the same way. If too many heavy metals get inside their cells they can damage the plant and make it sick.

One way that plants prevent heavy metals from entering their cells are by binding up the heavy metals before they make it inside. How do they do that you might ask? Well it is a pretty ingenious system. It has to do with their cell walls. Okay a little review. All cells are basically a sac (a bi-lipid membrane sac) filled with mainly water and other neat cell innards. Vertebrate animals give their cellular bodies structure with internal bones, insects have an tough exoskeleton that gives them shape, and plants have cell walls that help to keep them upright. Each of their cells is surrounded on all sides by these rigid cell walls that are connected together across the entire plant body. Without the cell walls plants would be a floppy mess.

Back to the connection with lead. The researchers determined that the moss plants, particularly at the protonema (filamentous) stage bound the lead to their cell walls so that it would not enter the cells. When placed in a lead bath they could even change the chemical composition of their cell walls to bind up (sequester) even more of the lead. This method does not keep all of the lead out of their cells but it is a good start. This phenomenon has been observed in the roots and pollen tubes of other plants. Boy plants are awesome!

Click on the citation below for a link to the paper.

Mosses in Malaysia

Well I sure had a whirl-wind adventure traveling around southeast asia for 2.5 weeks. The itenary was as follows. I flew from New York to Kuala Lumpur, Kuala Lumpur to northern Borneo (then back), Kuala Lumpur to Java (then back), I stayed put in Kuala Lumpur for a few days, and then home to Connecticut.

My favorite part of the trip was Northern Borneo. We were in Sabah, Malaysia near the town of Sandakan. We roomed at the Sepilok Jungle Resort, and I thought that it was a nice place to stay despite the poor review it was given in the most recent Lonely Planet Malaysia. We visited the Sepilok Orangutan Rehabilitation Center and the Rainforest Discovery Centre, both within walking distance of our lodging. With the rainy season upon us, we didn't get to explore aroung the rainforest nearly as much as I would have liked. Here are some of the mossy photos from the adventures.

All available surfaces were covered in mosses including tree trunks, fallen logs and hanging vines.

Here we have some mosses in the Calymperaceae. They are a very common family in the Pacific Tropics. Their identifying feature are the clusters of gemmae at the tips of the leaves.

 Some tiny critters like this ant were hiding among the mossy cover.

A few of the species that I saw had some tiny sporophytes rising above the leafy gametophytes.