Seen any good grass flowers lately?

Our summer is rushing along, as summers usually do. With the abundant rains this year, grasses are growing profusely and the grass flowers have been a treat to see. If you ask most people, they will say that grasses don’t have flowers. It all depends on what you consider a flower. The common notion is that a flower has to be colorful and showy. That’s fine if the flower is pollinated by an insect or other animal, but wind-pollinated flowers don’t bother with all that extravagant use of resources. Their flowers are the most basic models - tiny petals or none at all, no scents, no nectar. The wind doesn’t work any better with those things than it does without. All it takes to be a flower is a stamen or a carpel, and grass flowers have both – one to three stamens and a two-carpellate pistil usually.

Here are typical grass flowers. The anthers are yellow and the stigmas are feathery and white.

I’ve been asked what grass flowers look like, and that’s a good question. Without a hand lens or other magnifier, it is hard to see them at all. Basically grass flowers form within a series of bracts – small modified leaves, which are usually green. This little package of flowers and bracts is called a spikelet. Each spikelet can have one to several flowers + bracts stacked together. When the flower is mature, a pair of little scales (the lodicule) at the base of the ovary swells and prys the stack of bracts apart. The stamens, typically three of them, dangle out on long, flexible filaments. The anthers are large compared to the size of the whole flower. They have to be to shed enough pollen. Wind tends to scatter pollen and dilute it. The stamens are the easiest part of the grass flower to see. The pistil typically has two styles and two feathery stigmas. If you would like more details on grass flowers see http://www.backyardnature.net/fl_grass.htm

The feathery stigmas have a large surface area to snag pollen. Their structure may also alter air flow, making it more turbulent and promoting pollen contact with the sticky stigmas. The stigmas are often white, but there are many colors in various grass species. After the grass flower has bloomed, the bracts close back up and there is little of the flower to see on the outside of the spikelet. Sometimes the stamens remain for a short while after the bracts close. Inside, the ovary of the flower is developing into a closed, dry fruit. The layers of the ovary wall adhere closely to the seed, so the whole thing is commonly called a seed or a grain. A kernal of wheat, for example, is technically a grass fruit.

This switchgrass has orange anthers and pink stigmas - pretty fancy for a grass.

The grass family is one of the largest of the flowering plant families, so my photos show only a tiny fraction of the variety of grass flowers. It’s another good challenge for field work – find the grass flowers. Happy hunting!

 

Many flowers in this grass inflorescence are blooming.

Postscript on slime molds

My tomato plant has a slime mold!

Slime molds seem to be traveling lately. For the first time, one of them appeared in a pot in my greenhouse. I was away for a few days and didn’t catch it in the act of crawling up on the side to form its spores, but there it is. I wonder if I brought the spores into the greenhouse on my hands or clothing after I found (and poked) the one under the juniper tree.

Once my cucumbers had mushrooms, a species that is considered a pest in greenhouses. I suppose it shows that fungi and slime molds spread themselves far and wide, like other organisms that depend on tiny spores for reproduction. Once in a while a spore lands in a good place to grow and that makes up for the huge numbers of spores that don’t grow into anything.

Stalking the wily slime mold

This slime mold aggregated under a juniper tree.

We have had a wonderful series of rains along the Colorado Front Range, and many moisture-sensitive organisms are showing up. The picture shows one of the less photogenic of the slime molds, probably from genus Fuligo. I was surprised to see this one preparing to form its spores in the thin duff under a juniper tree. The first time I saw it, it was a spongy, cream-colored mass. That day I hadn’t brought my camera – a lesson for me to be more prepared this time of year. I went back the next day and took this photo. The mass had shrunk and liquid pools appeared on its surface as it converted to spores.

Slime molds are incredible creatures that spend part of their life cycle as individual cells and part as a multicellular or multi-nucleate structure. They have a more attractive name – the social amoebas, but more information is listed under “slime mold.” The basic life cycle of social amoebas involves spores that germinate into individual cells. These amoebas eat bacteria from decaying plant materials. When food runs low, the cells send out a chemical signal that calls all of their kind to come together and make spores. The spore-bearing structures can be elaborate and beautiful, but they are small and easily overlooked. If you want to see a variety of them, go to this listing, http://www.uoguelph.ca/~gbarron/myxoinde.htm. For a story about hunting slime molds in the Great Smoky Mountains National Park, see this article from Smithsonian Magazine: http://www.smithsonianmag.com/science-nature/phenom_mar01.html. The Discover Life website has good information and photos as well: http://www.discoverlife.org/20/q?search=Eumycetozoa.

It is easy to bring a slime mold into the classroom. To make its home, you need an empty Petri dish or similar container, some paper towel, and few flakes of old-fashion oatmeal. Scientific supply companies sell the dried form of the organism, Physarum polycephalum. It is a resting structure called a sclerotium. If a slime mold in its active state dries out, it can form a sclerotium and hunker until the moisture returns. To grow the slime mold, cover the bottom of the Petri dish with clean, white paper towel, sprinkle in about a half-dozen flakes of rolled oats, and moisten this well, but don’t add so much water that there are puddles. Place the sclerotium in the dish. Don’t worry if it looks like lots of orange flakes – the parts will find each other and come together. Place your culture in a re-sealable plastic bag to retain moisture and to keep the slime mold from migrating out. Put the whole thing in the dark to prevent the organism from forming spores. The yellow slime mold will become active and move around the Petri dish. When you are finished observing the slime mold, you can put it in the light and use a magnifier to look for the spore-bearing bodies – small black structures that give it its name, the many-headed slime. To see photos of this slime mold in several stages, see the first link above. Here’s a link to more culture information: http://www.educationalassistance.org/Physarum/EasyToGrow/PHYSARUM%20culture%20for%20web.html.

Slime molds are members of the unikont branch of eukaryotes and the amoebozoa branch of unikonts. They make up the mycetozoa branch of amoebozoa. The term “myxomycetes” is used for the acellular slime molds, those whose amoebas fuse together into one big mass. Older classifications placed the slime molds in the fungus kingdom, to which they are only distantly related.

If you want to stalk the wily slime mold, a magnifier is a great help. Wet weather, decaying vegetation, and patience are also needed. Happy hunting!

What makes influenza so changable?

An influenza virion (single particle of virus)

With all the publicity over the new swine flu strain, students may be asking questions that are hard to answer. I have found the information in children’s literature to be limited. It doesn’t do a good job of explaining the influenza virus and its ability to change so rapidly.

First, let’s look at what is in an influenza virion – a single particle of the virus. In the center of the virion, there is a coil of RNA complexed with protein. This coil is wrapped in a viral envelope, which is a membrane the virus modifies and takes from its former host cell. There are viral proteins on the outside of the membrane. They look like little knobs sticking out from the virion surface in the photomicrograph.

This illustration, which is a public domain image from the Centers for Disease Control, was made by spreading the virus on a transparent film and adding a stain that blocks electrons. The stain filters down into the low spots and makes them look dark in the photomicrograph, which was made with an electron microscope. Virions of almost all viruses are too small to see with a light microscope. Influenza virions are about 1/20 to 1/10 of a micrometer in diameter. Their host cells have diameters that are thousands of times larger.

The RNA carries the instructions for how to take over a host cell and turn it into a virus factory. Viruses can have RNA instead of the DNA that cells use to hold information. That’s not what makes influenza unusual. Most viruses have their RNA or DNA (they have one or the other, not both, like cells have) in a linear strand or a closed circle. Influenza has its RNA in eight separate pieces.

When influenza replicates, its RNA-protein complex enters a host cell and uses the cell’s resources and machinery to make many copies of the molecules that make up its virion. As the cell fills with viral RNA and proteins, the eight pieces of RNA that make a complete set of viral genes form a complex with protein. Then this nucleic acid-protein complex moves to the cell membrane, to areas where viral proteins have been inserted into the membrane. It buds out of the cell and gets its envelope in the process.

Now if only one virus has infected the cell, then the virions will have the RNA from that virus alone. It is possible, however, for two different virions to infect the same cell. When that happens, the resulting virions can hold an assortment of RNA segments from either virus. The RNA segments are packaged randomly, so they can have many new combinations of genes. Instantly new strains of influenza arise that may have different proteins on the outside. If a person has not been vaccinated against those proteins or has not been infected by a strain of influenza that has those proteins, then the new virion may be able to spread very well in its host. That’s good for the virus, but bad for the person.

Another complication with influenza is that there are strains that infect birds and mammals such as pigs, as well as people. This new influenza virus was called swine flu because some of its genes appear to have jumped from pig influenza virus to a strain that infects people. This may have happened if a sick person and sick pigs were in close company. Note that pork meat cannot carry influenza virus, and eating pork certainly can’t infect people with influenza.  

Now back to the little knobs on the outside of the influenza virus – they are called hemagglutinin and neuraminidase. When a person has antibodies to the neuraminidase, they keep the virion from entering a host cell. This means that the antibodies protect the person from the disease. Strains of influenza are named for the type of their hemagglutinin and neuraminidase. The new swine flu strain is called H1N1, because its hemagglutinin and neuraminidase both type 1. Human influenza viruses usually have H1, H2, or H3, and N1 or N2. There are many other types of these outer proteins in the virions that infect other species (and occasionally jump to humans). The H1N1 designation doesn’t tell everything about the virus. Within this type, there are mild and severe virus strains. After all, there are several more genes in the virions.

The big question is “What can we do to protect ourselves from the flu?” One thing that is seldom mentioned is to get more sun exposure or take a vitamin D supplement. There is increasing evidence that high vitamin D levels are important for good immune function and that influenza infections increase as people’s vitamin D levels drop in winter. With summer on its way, it will be easier to get some sun – just don’t get sunburned. Enjoying the outdoors and nature while getting sun exposure ought to be a fun, easy, healthy thing to do for yourself.

Classifying buttons vs. life

 

Buttons can be classified in many ways

If you want to teach someone about classification, a pile of assorted buttons is a good tool. It is always interesting to have two or more groups working on a button classification and see what criteria they use. Buttons make a fine model and come in enough variations to make classifying them interesting and even challenging. However, there is more to classifying life than classifying buttons. Life has another dimension.

 Buttons are here-and-now objects. Big buttons don’t have little buttons and they don’t pass on information to offspring. They have no history that we can observe and they share no ancestors. Buttons carry no information about their past. Classifying them is a good model for what Linnaeus did when he classified life. He felt, at least for most of his career, that all life had been created instantaneously and had always been and would always be just as he saw it.

Life has important differences from buttons. Darwin’s work was very important in calling attention to life’s history and to the idea of evolution, which he called descent with modification. We now have overwhelming evidence that life changes through time and all living species have a long history. Fossils tell a good deal of the story, but the “second fossil record,” the DNA in each organism, is what has allowed us discover much more of the story.

Each species had ancestors that stretch back in time. For the story of the many human ancestors, see The Ancestor’s Tale by Richard Dawkins. This inspiring book has its own Wikipedia entry, in which the ancestors it visits are listed. http://en.wikipedia.org/wiki/The_Ancestor’s_Tale Connie Barlow describes associated experiential activities for children at The Great Story website. http://thegreatstory.org/ancestors-tale.html

Two species may be descendents of a common ancestor that lived in the not-so-distant past. Biologists strive to place these sorts of close cousins in the same group, a lineage that includes the ancestor and its descendents. Other life may have shared an ancestor with our cousin species, but much further back in time, with many more lineages also sharing that far past ancestor. This may be shown on a Tree-of-Life diagram as a deeper branch from earlier in life’s history.

How can we model descent with modification? Once at a teacher’s workshop I used chocolate candy. We had plain miniature chocolate bars, bars with nuts, Hershey’s Kisses, and Hershey’s Hugs. We made a branching diagram that illustrated our hypothesis of the descent of these candies. The best part was eating the samples after we had finished with our phylogeny.

Maybe there is no suitable model for classifying life other than life itself. It certainly won’t be boring.

Flowers on trees

Spring is bloom time for angiosperm trees (that’s trees other than conifers and ginkgoes) in temperate climates. Trees have two basic approaches to flowering, make big showy flowers and use insect pollinators, or make lots of small, inconspicuous flowers and use the wind to transport pollen. I saw both of these lately.

Staminate and pistillate (arrow) catkins of alder bloom in early spring.

The alder was in flower in mid-March. It had formed the buds of its inflorescences last summer, so it was ready to go when the weather warmed. Trees with wind-borne pollen must bloom before their leaves bud out. The pistillate flowers form in little catkins, marked by the arrow in the photo. The bracts between the flowers persist and enlarge as the ovaries develop. When the fruits mature in the fall, and the seeds are shed, the bracts remain. They are the structures in the back that look like miniature brown pine cones. The staminate catkins are much more conspicuous in bloom, but they fall off after they have released their pollen.

Alders in most areas of the US are likely to have bloomed by now, but their cousins, the birches, are yet to flower. Birches have similar staminate inflorescences, and these also form the previous summer. The pistillate flowers are borne on an upright catkin-like inflorescence. When the fruits are mature, the bracts and the seeds are shed, leaving a bare stem. Some of the bracts may not be shed by spring, but you can easily tell a birch from an alder by the little cone-like structures on the alder. Their cousins, the hazelnuts have similar staminate catkins, but all you can see of the pistillate flowers is a cluster of tiny red threads sticking out some bracts.

The tiny red thread-like styles of a hazelnut protrude from a cluster of bracts

The pear tree, on the other hand, is very showy with its white-petaled flowers. It is a member of the rose family, whose flowers have either one carpel or several carpels distinct from one another. The pear and the apple typically have five carpels. You can see the five styles and stigmas in the photo below. The flowers of cherries, plums, apricots, and almonds look a great deal like apple and pear flowers, but the stone fruits have only one carpel. The immature anthers of the flower are pink. As they mature, the anthers split and peal back, revealing the pollen. The anthers shrink and darken when they are mature.

Be sure to observe and point out blooming trees to your children this spring. They may not notice without your help. They will likely be interested in the sequence of fruit development, once they see the flowers.  

This pear flower has five green styles and stigmas.

 

New Plant Kingdom ideas & new cards and chart

Sori on the leaf of a leptosporangiate fern

I recently revised my photo cards for the plant kingdom. They were previously called “Phyla of the Plant Kingdom.” With most of the phyla no longer being used, the title had to change. Now that set is called “Major Branches of the Plant Kingdom.” It still has 40 cards and each card still carries the classification on the back, but there have been changes to the text. I also put in some new photos, such as the one for the leptosporangiate ferns. There are new clearer photos for some of the mosses and club mosses. I’ve combined some illustrations onto one card and added two new families of conifers, the juniper/redwood family, Cupressaceae and the yew family, Taxaceae.

If you are introducing the plant kingdom to elementary students, I recommend the revised Plant Kingdom chart from InPrint for Children. http://www.inprintforchildren.com/store/  Carolyn Jones has done her usual high quality design job and added color to the individual illustration cards that go with the chart. Please note that she is closing retail sales soon, but her charts will be available from Montessori Services. http://www.montessoriservices.com/store/

New Plant Kingdom chart from InPrint for Children

I’d like to go back and make one more stab at explaining the changing view of the plant kingdom. The bryophytes still have phylum names, so I listed them on my cards, but it would be perfectly OK for precollege levels to simply call them by their common names – liverworts, hornworts, and mosses. These three lineages are monophyletic (“one lineage”) and they have a similar type of life cycle and yet it isn’t totally clear if they share a recent common ancestor. They could be shown on a separate branch or as three separate branches coming from the plant kingdom before the vascular plants branch off.

The first branch of the vascular plants is the lycophytes. If they are a phylum, then the other phylum would have to the euphyllophytes (“true leaf plants”), which is both the monilophytes (fern lineages) and the seed plants. If the fern lineages were to have phyla, there would have to be one for the whisk ferns and the ophioglossid ferns (adder’s tongue and grape ferns), one for the horsetails, one for an obscure group of tropical ferns, and one for the leptosporangiate ferns. The seed plants could have phyla for the gymnosperms and angiosperms or for each of the major seed plant lineages or??? More data is needed, but maybe it is just time to discard phyla for the plants. The view of the full lineage for each group is a much richer view.

(Disappearing) phyla of the plant kingdom

Whisk ferns are a part of the fern lineage. They are no longer a phylum.

I noticed last year as I was writing my book, Kingdoms of Life Connected, that plant systematics textbooks were not using phyla, except for the bryophytes in some cases. What’s going on here? It is nothing less than a new view of the plant kingdom and of the classification of life.

Our traditional view was set by Linnaeus, back in the mid 1700’s. His system was based on the assumption that all life had been created simultaneously and that it was unchanging. He based his work on the appearance of the organisms and placed them in the hierarchical categories that we still (sometimes) use – kingdom, phylum, class, order, family, genus, and species.

Now botanists look at the lineages for each group of plants. For example ferns can be seen as members of the plant kingdom (embryophytes), vascular plants (tracheophytes), true-leaf plants (euphyllophytes), the fern lineage (monilophytes), and finally the branch of the leptosporangiate ferns, sometimes called the true ferns. This is a much richer view than a simple box labeled “ferns.”

What Linnaeus missed is the history of each organism. Darwin bought forward the important idea that organisms have histories. Some share a recent common ancestor, others do not. The history of an organism doesn’t show up in a row of boxes. Instead it must be displayed as a branching diagram that shows which organisms are more closely related. 

Getting back to the plant kingdom and how we introduce it in the elementary classroom – usually the plant kingdom was broken into phyla (or divisions if you prefer the traditional name). Most of children’s literature – the small body of learning resources that actually address the plant kingdom – use phyla, whereas college texts and professional botany writings have largely discarded that category for plants.

Why have most of the phyla names been dropped? They didn’t work with the new view. The horsetails were previously placed in their own phylum, but they are embedded in the monilophytes, the fern lineage. So are whisk ferns, the psilophytes. The phylum name is even less useful for whisk ferns because it excludes their close relatives, the grape and adder’s tongue ferns.

Will phyla come back? It’s not impossible, but it may take a while for botanists to settle on what to call a phylum. Is it a branch of the ferns, the whole fern lineage, or the euphyllophytes? If children know the main branches of plant life, they are well-prepared whatever system develops. The animal kingdom, by the way, has kept its phyla, although they are now grouped into different lineages than they were a decade or so back.

Another term to discard is “seedless vascular plants.” The vascular plants have two branches, the lycophytes (club mosses and their relatives) and the euphyllophytes. The latter has two branches, the monilophytes (ferns in the broad sense) and seed plants. Club mosses shouldn’t be in the same category as the ferns, and “fern allies” mixes unrelated lineages.

For children to see the current view of the plant kingdom, they need a branching diagram that shows who is related to whom. Rows of boxes are out, phylogenies are in. A phylogeny is a branching diagram that illustrates a hypothesis about the evolution of organisms. Actually, the word applies both to the hypothesis and to its illustration. For more about current phylogenies, see my book, Kingdoms of Life Connected: A Teacher’s Guide to the Tree of Life and take a look at the charts that are available for free download from my website, http://www.bigpicturescience.biz.

 

Another term for a phylogeny is a Tree of Life or, informally, a family tree. The Tree of Life web project (http://tolweb.org/tree) has a great illustration in its home page. If you go to the page for the plant kingdom (aka embryophytes), you will see the extant lineages and a number of extinct ones. See http://tolweb.org/Embryophytes/20582. It is always thought-provoking to see the extant lineages in the matrix of extinct ones.

What should you do with your old plant kingdom charts? Keep them for historical perspective. Children’s literature still shows older classifications. Older charts also help children see the changing nature of science thought. Just make sure that children have working knowledge of the new, phylogenetic view of life.

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