Field of Science

The Color of Light

Sunshine, to our human eyes the light appears white, but buried within are all the colors of the rainbow. In order for you or I to detect the colors that compose white light we need help. Shining light through a prism is one way I know to separate light into its many colorful components. Plants, on the other hand, need no such help. They have proteins called photoreceptors that enable them to detect different wavelengths of light. There are several different types of photoreceptors. Phototropins sense blue light, phytochromes sense red light, and neochrome is a chimeric protein that has the ability to sense both blue and red light. 

Light, especially the blue and red portions, are the main types plants use to run their photosynthesis machinery. When taller plants shade out shorter plants they alter both the quantity and quality of the light that reaches the plants below. Thus it is important that plants can detect the light quality in order to respond appropriately, by either growing away from shady spots or altering how they develop. 

A few ferns hanging out with their mossy pals.
A recent study was published that literally sheds some light on the evolution of these light sensing photoreceptors. Neochromes, the light sensing proteins with dual abilities, are present in only two groups of plants, the green algae and the ferns. Previously, scientists thought that these two groups independently evolved neochromes. But this new research proposes a different explanation. They found that the hornworts, a small group of bryophytes, also have neochromes and their proteins are closely related to those in ferns. They are so similar in fact that they were most likely transferred from hornworts to ferns. 

Horizontal gene transfer is a pretty wild thing that can happen in biology. One organism, potentially distantly related to another, can transfer some of its genetic code to another organism. If it is helpful the organism will keep the new piece of DNA, use it, and pass it on to its offspring. Scientists think that neochromes were very useful for ferns. Growing in the shadows of taller flowering plants, neochromes enabled ferns to take full advantage of low light conditions, thrive, and diversify. I think the ferns should send a thank you note to the hornworts for that super useful gift. The transfer of neochromes from one to the other happened over 150 million years ago, but you know what they say, better late than never.

Fay-Wei Li, Juan Carlos Villarreal, Steven Kelly, Carl J. Rothfels, Michael Melkonian, Eftychios Frangedakis, Markus Ruhsam, Erin M. Sigel, Joshua P. Der, Jarmila Pittermann, Dylan O. Burge, Lisa Pokorny, Anders Larsson, Tao Chen, Stina Weststrand, Philip Thomas, Eric Carpenter, Yong Zhang, Zhijian Tian, Li Chen, Zhixiang Yan, Ying Zhu, Xiao Sun, Jun Wang, Dennis W. Stevenson, Barbara J. Crandall-Stotler, A. Jonathan Shaw, Michael K. Deyholos, Douglas E. Soltis, Sean W. Graham, Michael D. Windham, Jane A. Langdale, Gane Ka-Shu Wong, Sarah Mathews, and Kathleen M. Pryer. Horizontal transfer of an adaptive chimeric photoreceptor from bryophytes to ferns. PNAS, published ahead of print April 14, 2014, doi:10.1073/pnas.1319929111

Additional coverage of this research can be found at these links: National Geographic, ScienceDaily, and The Economist

For more on plant colors, check out Johnna's April edition of the Berry Go Round plant carnival. My favorite is the post about the iridescent fruits of Pollia condensate. Pretty cool that they are the shiniest living things on Earth!

A Video on the Moss Life Cycle

Take a break from your regularly scheduled program to check out this video on the moss life cycle. I would definitely recommend this video to students learning about mosses or bryophytes in class or for anyone who wants to brush up on their plant life cycles.

Overall I think that it is a nice video with accurate information. There was only one typo that I saw. The maternal gametophyte cap covering the sporophyte apex during its development is called the calyptra. No e after the t. 

Hat tip to Dr. Juan Carlos Villarreal for sending me this video from YouTube. 

Learning mosses at SOBEFREE

At the end of March I attended the SOBEFREE foray with amateur and professional bryologists from across California and beyond. I highly recommend attending this foray, especially if you live in California. This year we went to some really great locations in Santa Cruz county and I learned tons of California mosses. The days are spent hiking and collecting mosses with our permits in hand. Then the evenings we all gather around our microscopes to look at the plants and to identify them to species.

With my new skills in hand, I decided to take a look at some of my older photos to see if I could make any identifications. I looked at my desktop calendar from January and now recognize the species. It is Dendroalsia abietina! It is a super common moss on trees in California. When dry the leaves curl downward and may remind you of a clenched fist. When wet, the fronds are splayed out and form an array of small shelves across the trunk. Peek beneath the fronds to find the short sporophytes hiding on the undersides in clusters. I love learning the names of new plants, especially mosses. I often think of it as making new botanical friends.

Being out in the field and looking at plants was such a great change of pace from being in the laboratory. I am hoping that I can make it to the Schofield Bryophyte and Lichen foray up in British Columbia this fall. I don't think the time and location have been announced yet. As soon as I hear I will share it here on the blog.

It would also be nice to stop by the University of British Columbia while up in Canada to meet the chemists I am collaborating with. I have only interacted with them through email and skype. It would be great to see them and their lab setup in person. 

Keep your eyes peeled for the announcement about SOBEFREE 2015, which will be held in March somewhere in California. I will most certainly be there next year! 

April 2014 Desktop Calendar

This moss and lichen combo is from my trip last month to Yosemite National Park. I only did photographic collecting and I am still improving my California identifications, thus I was planning to post this calendar without species identifications. But after this weekend's SOBEFREE (a spring outing in California for professionals to head out into the field to observe, collect, and identify bryophytes) I am ready to take a guess.

From the photo this bryophyte appears to be Orthodicranum tauricum. This species may remind you a bit of Dicranum. They both have narrow thin leaves and upright stems. Unlike Dicranum, the leaves of Orthodicranum point in many directions. In Dicranum the leaves are falcate (meaning sickle-shaped) and secund (all pointed in the same direction). It gives Dicranum one of it's common names, broom moss. It looks like the floor has just been swept using a stem and the leaves are now curved and pointing all in the same direction. But I wouldn't recommend it for floor sweeping. It would take way to long to get the chores done.

Anyone have any thoughts on an identification for the lichen? Lichenological books are no longer at my fingertips in my lab here in California, but it would be great to learn the genus or species if someone is familiar.

April Desktop Calendar
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.