Monday, March 26, 2012

This Bud's For You

So the big question is, how far did our Boston plants break dormancy last week? We had an extended spate of very warm days, bright sunshine, and all the ingredients necessary to bring out the flowers, and to an extent, the leaves. Our magnolia, our forsythias, and all the cherry trees in the neighborhood were out in full bloom. Now the weather has gone back to March. The next couple of nights we should see below freezing weather. What happens to the plants?

Lilac Buds

The short answer is, it depends what plant it is. The flowering plants like magnolias don't depend on their flowers to survive. Reproduction, normally the role of flowers, is obviously not essential in our urban garden environments.


But the leaves are another story. Have you ever noticed that on most of the trees, it's the flowers that come first and later the leaves? Plants in the temperate and cool zone have evolved so that the leaves come out of dormancy last. And there's a reason for this. A late frost will kill off young leaves, depriving the tree of nutrients and potentially killing it.

Sycamore tree disease

So let's look at the question a little closer. Excluding the flowers, which we've already callously determined as unnecessary, what about the leaves? Again, it depends on the species. Most of the shrubs and trees I've looked at still have their leaves tightly packed in buds. They may not have even begun the process of breaking dormancy. But in case they have, two things might still protect them.


First, structural anatomy. If you look carefully at most angiosperms (flowering plants) you will see that in addition to the main bud, which breaks dormancy first, there is at least one other bud held back in reserve. The beech leaf below is a perfect example.

Beech leaf

...or this birch.

Birch leaf

Many layers of vegetative covering also protect the young buds. They are slow to lose these layers.

Lenticels and Gas Exchange

Juglans regia

A more complicated and perhaps less well understood protective phenomenon is the suite of metabolic and chemical conditions each plant has evolved into. Buds sheathed in a waxy coating are one example. They are full of anti-freeze and surrounded by anti-freeze. And they are well protected until the cascade of dormancy-breaking reactions starts.

Woven willows

So even though the weather has unpredictably swung back from July to March, I am pretty certain that thanks to millions of years of experience with this sort of thing, the plants have it in the bag.

Friday, March 23, 2012

No More Cars?

I read a cool article in the New York Times this morning where they wrote that large numbers of young people are no longer interested in cars. What an amazing proposition. I wonder why it is?

Wasting Energy

Cars are controversial. This sounds less radical now than when I was growing up in the '60s and '70s, when car ownership was part of the American Dream. There are so many reasons that cars are problematic. I won't go into them here, well, at least not most of them.

Chelsea Stacked Cars

But all this reminds me of a presentation my students gave the other day. They were talking about solar energy, which they claimed had about a 20% efficiency rate. This didn't sound half bad to me. After all, solar energy is emission-free and relatively low-impact. If you compare it to the efficiency of the internal combustion engine (about 5% of that energy is transferred from your gallon of gas to the wheels of your car) it's an incredibly effective way of capturing light energy.


During the Q & A after the presentation I thought there was a pretty good "teachable moment." Last semester we learned about photosynthesis. With all the discussion of the internal workings of the chloroplast I didn't have a chance to discuss energy efficiency with my students. But here was my chance. Internal combustion motor, approximately 5%. Solar power generators, approximately 20%. Photosynthesis? About 33% efficiency.

Light and palm

How does this translate? About 33% of all the light that hits the leaf goes into the production of sugars that build the plant body (cellulose) or fuel the respiratory process (glucose). Pretty amazing way plants have evolved to utilize sunlight.

Thursday, March 22, 2012

Magnolia Universe

In our garden in Cambridge, Massachusetts sits a magnificent Magnolia stellata shrub. This year there are more blossoms than ever and we are having a chance to enjoy them through the warmer-than-usual days.

Rush of Spring

I'm curious about the visual and olafactory presence of this wonderful plant. Before the leaves emerge we perceive it as an orb of aromatic white blossoms. They shine in the daylight sun and at night, as they close, they seem to radiate a gentle light. Their aroma is heavenly, perhaps the most memorable smell of spring. The graceful branches seem to dance with floppy-edged stars. The magnolia seems to be here for the sole purpose of decorating our lives. Within this aesthetic universe there are suggestions of questions we might ask as we inhale the early springtime pleasure.


What is the surface topology of the shrub? Is it a pure sphere or slightly flattened? How does the surface arrangement reflect the internal placement of blossoms? The flowers are spaced in a way that we perceive as aesthetically pleasing, but might their placement provide selective advantage for this plant? Might the internal (and external) universe of magnolia blossoms enhance pollination? Aroma production? Visibility? Or are all of these questions moot? Perhaps the magnolia spreads at our pleasure, its superb features a kind of symbiosis with the world of gardeners.

Magnolia stellata

As scientists we look at the world a little differently from our neighbors. We see things that are visually pleasing and we ask what's underneath our feelings of delight. We wonder about the aesthetics of evolution, trying to imagine the perceptions of a bee or the circulation of a breeze. We look inward at ourselves with curiosity as we wonder about the mechanisms of wonder.


Monday, March 19, 2012

Is This Global Warming?

Boston experienced its warmest winter ever and the past couple of weeks have been way warmer than usual. By this Thursday we are supposed to hit a record-shattering 86 F, weather that belongs in July or August. My students, my neighbors, and it seems everyone is asking "is this global warming?"

Miniature Tulips

The short answer would have to be "no." If you check out today's New York Times weather map you will see a simple explanation for this weather. On one side of the continent the jet stream has dipped way south, providing the West with unusual coolness and rain, even into Phoenix. Meanwhile, the pattern of the jet stream in the midwest and east coast is experiencing the "flipside" of the circulation coin, traveling far to our north.

Growing Storm on the Prairie

So, simply put, the flow dynamics of the jet stream, while unusual, are immediately responsible for this weather.

Another part of the Boston we boast that the month of March lasts here for ninety days. What do we mean by that? Again the simple answer is that the Atlantic Ocean, a huge body of water that takes relatively long to warm up in the spring, is right at our front door. Ocean breezes come inland through June, taking even the warmest days down into the 50s. Why isn't that happening now? Simply because the southwesterly flow of air, which is linked to the flow of the Jet Stream, is strong enough to keep an onshore breeze from occurring. The result? We stay warm.

The Great Boston Smokeout

A third part of the story is explained by our weather last week. A "back door cold front" bathed the city in cool ocean air carried on a breeze from the northeast. This wasn't a nor'easter because there was no precipitation involved with it. It was simply part of the dynamic of an air current circulating around a high pressure area to our north and east. The weather last week was more like San Francisco than Boston, consistently cool, oceany, and never warming up even in full sunlight.

Structure and Function

So, it all these patterns point to a "no" for global warming, why do scientists insist that the phenomenon is real?

For an answer to this question all you have to do is go to the superb "Earth Observatory" sponsored by NASA. All kinds of interactive maps will show you that there have been long-term warming trends, not necessarily on land, not necessarily in the temperate zones where most people would notice it, but in the Arctic Ocean and waters adjacent to it.

Scientists have demonstrated without question that the planet is warming by using simple methods of observation. That doesn't mean we notice it on a day to day basis. Certainly if we compare last winter's notable cold and abundant precipitation with this year's winter, we see a big difference. But that is not the evidence for global warming.

Metermaid's Dilemma

Tiger in the Snow

Snow Slide

Global warming and global climate change are planet-wide phenomena that are measured not day to day, but over decades, and not in a single locality like Boston, but all over the Earth, including our oceans.


Enjoy the nice weather but think hard about how your own activities can calm the trend to global warming. Walk, ride a bike, or take public transportation instead of driving. Turn down the heat and skip the AC. Eat less meat. Try to travel less by air.

Saturday, March 17, 2012

Order and Disorder: Ecology and Necessity

Working on my doctoral research at Harvard I was preoccupied with order. As a taxonomist, I studied the order in which species were arranged. The order of taxonomic conventions, the historical order in which things were named, making "order" out of a natural universe that seemed "disorderly," one that the right ideas might arrange appropriately. After many years of working and finally achieving the status of "Doctor of Philosophy" in Botany, the order started to resemble ordure.

Lichen perfume: Oak Moss

In all fairness, it didn't seem that way at the time. A hard-won thesis, good grasp of species concepts, and a fine (if I do say so myself) statistical paper correlating species distributions to geography, were ample reward for all the work and sacrifice. And I can say I looked forward to a strong current of research as I studied the fascinating world of lichen morphogenesis.

Cladina rangiferina

So, what's with the order and disorder? I didn't set out wanting to write about my PhD work. It's pretty much ancient history anyway.

Weird fungal cell

I started this post thinking about garden landscapes. Garden aesthetics go in and out of style (so do scientific ideas, believe it or not!) and they seem to reflect something of the society in which they're created. I think I could do a whole thesis on garden aesthetics, something that, ironically, connects to questions of order and disorder.

Borrowed landscape

What do "ordered" gardens tell us? For centuries, botanical collections were arranged in some kind of order, whether the order reflected the "four corners" of the earth or the "order" in which plant families were arranged. Formal gardens created a world of order that followed particular aesthetic pathways.

Yew snowballs

During the Arts and Crafts movement of the late 19th century a kind of "disorder" came to represent garden design, a kind of aesthetic argument against borders. In a rapidly urbanizing, industrializing society, the desire to recall a more "natural" or "pastoral" setting dominated. Later, unruly "borders" repudiated this argument, whether knowing or unknowing.

Formal garden path

Our Cambridge, Massachusetts garden is all border. We couldn't help it. The ten-foot wide garden we tend surrounds one side of the footprint of the house in front. It's about 40 feet long and runs along the house in front of us. What would you do with a space like this?

Garden Green

As a botanist and something of an ecologist I recognize the "moments" of sunlight, shade, moisture, drought, and openness that occur in different parts of the garden. The plants that occupy the garden change each year. Sometimes it's because I planted something, sometimes a squirrel planted something. And of course things die. I build the garden each year based on these moments. As the garden matures, I set it up to provide color for more and more of the year. One of my goals is to nurture diversity. And there seems to be an uphill struggle against species that would overtake the landscape, since most of the plants we use in temperate gardens are prone to be weedy. Each year I struggle with what seems to be an eternal human question: What constitutes order--Neatness? Careful attention to detail? Good height relationships? Or is order something else altogether--a sort of "natural" order? How do we impose order on the landscape? What are our goals for tending the landscape? And if we fail to introduce or maintain order, what does "disorder" comprise?

Fake curves

Monday, March 12, 2012

Bathed in Bacteria: Interpreting our Past and Present

Pondering the antiquity of life on our planet I read that the first several billion years of life on Earth were bacterial. Single-celled life forms, the organisms that we lump under the name "bacteria," were the dominant, probably the sole living things for most of the history of our planet. What does this mean?


For one thing, the early Earth was what we would consider today to be a harsh environment. The "primordial soup" was anaerobic, a time stretching for billions of years in which free oxygen was absent. Without free atmospheric oxygen no ozone layer could form. And without the protective ozone layer, ultraviolet radiation, inimicable to most modern life forms, bathed the surface of the planet.

After the Storm

Many species of bacteria-like organisms, both known and unknown to science, now live in extreme environments that in some ways recall our ancient past. Smoking vents at the bottom of the oceans and sulfur hot springs are some of these environments. They provide partial evidence of what Earth used to be like.

Weird Fumarole

What else is implied by eons of bacterial presence on Earth? We know that photosynthetic bacteria began to thrive at a certain point in our history, and that so much oxygen was released from these organisms, our atmosphere switched to an aerobic, or oxygen-rich state. The presence of free oxygen in the environment was a revolutionary threshold on Earth. Because oxygen is a toxin. It strips electrons from other elements and changes their chemistry. As harsh as the early Earth was, life had to evolve further to deal with the presence of oxygen. Over the eons, macroscopic life forms that we recognize today emerged.

Wall of Iron Oxide

This leads me to the third "big" conclusion about our common history with bacteria. We evolved from them. Perhaps it is counterintuitive that the large, seemingly dominant plants and animals on Earth today, are just half-emerging from a bathtub filled with bacteria. But bacteria and other microbes still dominate our environment, both internal and external.

Tonina Stucco

Just as a bather lifting out of a tub full of water has water inside and all over their body, our insides are full of bacteria and so is our skin. Bacteria that process oxygen (mitochondria) live in every one of our cells. Without them we would not last for one second. Our soil, air, and water are full of bacteria. Plants and algae couldn't do photosynthesis without their chloroplast partners, bacterial descendants that live in every photosynthetic cell.

Birch leaf

We share a common genome with bacteria and because of this, we have much in common with them physically and metabolically. Why all this thinking and writing about bacteria?

Desert Pavement at Death Valley

I started a new sculpture project called "The First Billion Years." I'm making a thousand objects, each of which represents a million years of life. I could do this project three times over and still only represent bacterial life on our planet. It gives me pause, but it's also inspiring, to think that we share this deep relationship with life forms that seem at once strange and perhaps repellent.

Thursday, March 8, 2012

Simplicity = Design Success

Plants are amazing. Look at a plant and you see something deceptively simple. A stem, some leaves, buds, maybe a flower. What amazes me about plants is that they are structurally simple, but that they function in many complex ways. Simple structure, complex functions. Design elegance honed over hundreds of millions of years.

Let's look at a few examples. The leaves of this walnut tree give us picture of design simplicity. A thick central vein, branching vascular tissue, a pleasing color and texture.

Walnut compound leaf

If we look below the surface using a microscope we will see a world of complexity. Cells filled with chloroplasts (which do the photosynthesis), chloroplasts filled with membranes, proteins embedded within the membranes. All of these components add up to a very complex living environment.

It took scientists over 200 years to come to an understanding of the solar collecting apparatus inside the leaf! We are still asking questions about how it works. All this in spite of its visual simplicity.

Consider the delicate flowers of this Halesia tree. We appreciate them for their quiet beauty, perhaps noticing the unusual square-shaped ovary at the base of each flower.


When we look below the surface we see a complex series of cells, tissues, and processes that contribute to the reproductive success of this plant.

The simple, graceful shape of this succulent and its flowering stalk tell only a fraction of the story of a highly choreographed system that responds to minute changes in light, temperature, and moisture.

Succulent flower

And the beautifully arranged spiral of this sunflower suggest the depth of evolutionary experience through which its ancestors gathered hundreds of flowers together on a stalk, squeezing them together in a best-fit packing arrangement that promotes efficiency of pollination and seed dispersal.

Sunflower Fibonacci Spiral

All of these "designs" look simple. They feel simple. Plants tell us a story of simplicity through fusion of body parts, reduction of body parts, and a trend toward streamlining body parts. Simplification, fusion, reduction, and streamlining are some of the evolutionary "success stories" in the plant world. We have a lot to learn from them.

Tuesday, March 6, 2012

Mayan Symbols

As a botanist and a trained anthropologist I am very interested in the way various cultures have depicted plants. One of the great examples is corn (Zea mays). Corn emerged as a cultivated crop thousands of years ago in Mesoamerica and as a premier food crop it became prominent in the religion and iconography of the Mayans.

One of my favorite corn symbols shows the corn god emerging from the shell of a tortoise. This detail from a bowl found in present-day Guatemala shows the corn god as a germinating seed. The "face" is the crinkled corn seed, which seems utterly dry and devoid of life. The "headdress" depicts the young leaves of a new corn plant.

Resurrection of the Maize god

I have spent a good amount of time traveling in the Yucatan and it seems that wherever I travel, whichever archeological site I visit, there are depictions of corn. Compare this more recent, highly abstracted carving from the Pu'uc region to the older, more "literal representation" we observed in the Guatamalen bowl.

Kabah tree of life

Here is a similar symbol from Mayapan, not far from Kabah. It's interesting that here the symbol, which is nearly identical, seems to be upside-down. Was this a mistake that contemporary restorers made?

Mayan Symbol at Mayapan

I am struck by the unmistakable identity of a cob of corn from this stone carving on display at Palenque, one of the major Mayan sites, which sits deep in the rainforest.

Palenque Corn

It is similar to other more literal interpretations such as this one from Ek Ba'alam.

Ek Ba'alam maize symbols

Elsewhere at Ek Ba'alam corn is depicted as part of a mask.

Maize mask Ek Ba'alam

This is common in the Yucatan and in other parts of Mexico as well.

Corn deity

Fertility goddess

After Europeans settled in Mexico, the maize symbol continued, perhaps as an expression of indigenous autonomy. Here is an example from a colonial-era building in Mexico City.

Baroque corn decoration

One of the most amazing depictions of corn I have ever seen is very tiny. It is only a few millimeters tall. It is found on the back of a larger-than-life Catholic saint's reliquary that is on display at the Victoria and Albert Museum in London. Perhaps the corn symbol was put there by an indigenous metal worker who was putting the signature of his religion onto this object that was valued by the conquerers.

Maize depiction

Zea mays continues as a symbol throughout contemporary Mexico, a living icon of the grain that continues to nourish most of the people in this amazing country.

Modern use of corn


And just for the record...the world's first corn dog.

Corn dog