Being Green

Green. Why has green become the byword for things sustainable? And what is green - origin, function, symbol?

Green is on all of the color charts; it is the complement of red - when you focus on a green object and then close your eyes, the residual image glows red.

Green is at the center of the human visual spectrum - we detect and differentiate tens of thousands (even millions) of greens. In physics, that means we are most aware of impacts on light waves around 570 nanometers, at the center of our visual span, which runs from violet, at about 380 nm, to far red, at 750 nm.

This is not just the visible spectrum of light, it is also the biologically active spectrum. Wavelengths of light that are shorter than 380 nm border on the ultraviolet; they are more energetic than longer wavelengths and can be harmful to organic molecules, denaturing and destroying them. Wavelengths longer than 750 nm are increasingly infrared, less energetic than most visible light, playing out as heat. Light in the visual spectrum has the useful ability to affect organic reaction centers, to cause temporary, non-destructive activity that can drive chemical change.

Thus photosynthesis. The world we perceive from our green-centric viewpoint is powered through the blue and red light that drives photosynthesis. When blue and red light strikes photosynthetic reaction centers, electrons are energized, then lost into a chain of events, transported through a series of reactions that harvest the extra energy, storing it in chemical bonds. This newly bound-up chemical energy can be used at a later point to bond carbon atoms into chains that yield sugars and eventually the myriad of other organic compounds that make a plant.

But in passing along those electrons, the photosynthetic reaction center suffers an ongoing need for other electrons to reset the photochemical mechanism. Those replacement electrons, in effect, come from a powerful capacity to disassemble molecules of water. The photosynthetic apparatus is practically unique in its capacity to split water into oxygen, protons (hydrogen), and electrons. The oxygen we breathe was freed from water during ancient and on-going acts of photosynthesis.

The direct and curious relationship, then, between water and green is the capture of light during photosynthesis, from which there are by-products. Oxygen is left over from the water that was split. Green light is left over when the red and blue light are taken from the spectrum (though it is not this simple; there are other light-absorbing compounds involved.)

So plants are green because they do not use green light. Our world is green because green, photosynthesizing plants are the basis for life on Earth. How convenient! Green describes the range of colors we perceive best. And that all makes sense because our vision depends on non-destructive light-driven reactions. So it is no surprise that our vision and the photosynthetic process depend on the same special spectrum of radiation - visible light.

To flash red is to send an alert, to call a stop, to wave a flag. A green light signals the coast is clear, an open field. Green is our comfort color. Green is fresh, it is crisp lettuce. Green is living, like lawn or trees. So green has become the color associated with ecology, and ecology has become synonymous with environmental protection, which we associate with stewardship and sustainability. Thus green has become the color of sustainability, about which we have much to learn. And as Kermit tells us, it isn't easy being green.

Another Byt of Linnaeus

I introduced Linnaeus to the blog on his birthday, but I just can't be finished with him. His sexual system for organizing plants seems strangely sexist - the first slice at organization is based on stamens, the male parts. That isn't totally because science in the mid-1700's was a man's world, but there is a touch of that. Botanists always knew where seed were formed, and I guess the pistil and ovary had been given female associations. But Vaillant, in his 1717 lecture on the structure of flowers, was adamant about the noble role of pollen. Previously denegrated as worthless it was elevated by the new understanding that pollen is the male, it provides the sperm that brings life to an otherwise sterile egg. Linnaeus had grown up scientifically on Vaillant's lecture, and was charged up with the idea that anthers produce sperm for sexual reproduction. Now there were guys involved - the stamens - a new concept that seemed to stir the loins.

Anthers are so easily visible in flowers, and can usually be deciphered without slicing and dicing the parts. So given the new-found male pride in these now noble parts, no surprise that Linnaeus's system separates flowers based on the number and arrangement of stamens. And of course any ideological divisions bring artificial results, making for strange bedfellows. Any group of plants that has five stamens in their flowers will end up grouped together - regardless how very different they might be otherwise. And two plants that naturally should be grouped together would be pigeonholed in different places if one had five stamens and the other one ten.

Thumbing through Species Plantarum (1753), we can see some of the issues:
Class 1 - Monandria (One Stamen): Canna, Costus
Class 2 - Diandria (Two Stamens): Jasminum, Ligustrum, Olea, Syringa, Veronica, Justicia, Pinguicula, Verbena, Rosmarinus, Salvia, Piper
Class 3 - Triandria (Three Stamens): Ixia, Gladiolus, Commelina, Xyris, Cyperus, Scirpus, Saccharum, Panicum, Poa, Festuca, Arundo, Triticum, Eriocaulon
Class 4 - Tetrandria (Four Stamens): Leucadendron, Protea, Cephalanthus, Scabiosa, Houstonia, Galium, Buddleja, Plantago, Cornus, Trapa, Cuscuta, Ilex, Potamogeton
Class 5 - Pentadria (Five Stamens): Heliotropium, Myosotis, Cynoglossum, Pulmanaria, Borago, Echium, Primula, Azalea, Plumbago, Phlox, Convolvulus, Ipomoea, Campanula, Nicotiana, Physalis, Solanum, Ceanothus, Celastrus, Euonymus, Ribes, Hedera, Vitis, Vinca, Nerium, Asclepius, Chenopodium, Gentiana, Eryngium, Apium, Rhus, Viburnum, Turnera, Statice, Linum, Drosera, Crassula
Class 6 - Hexandria (Six Stamens): Bromelia, Tradescantia, Narcissus, Crinum, Amaryllis, Allium, Lilium, Tulipa, Ornithogalum, Asparagus, Hyacinthus, Aloe, Hemerocallis, Juncus, Oryza, Rumex, Trillium, Colchicum
Class 7 - Heptandria (Seven Stamens): Aesculus
Class 8 - Octandria (Eight Stamens): Tropaeolum, Rhexis, Oenothera, Gaura, Vaccinium, Erica, Daphne, Polygonum, Sapindus, Paris
Class 9 - Enneandria (Nine Stamens): Laurus, Rheum
Class 10 - Decandria (Ten Stamens): Sophora, Cassia, Schinus, Melastoma, Kalmia, Rhododendron, Arbutus, Clethra, Pyrola, Hydrangea, Saxifraga, Gypsophila, Saponarai, Dianthus, Silene, Lychnis, Oxalis, Phytolacca
Class 11 - Dodecandria (Twelve Stamens): Asarum, Rhizophora, Styrax, Portulaca, Euphorbia
Class 12 - Icosandria (Twenty Stamens): Cactus, Psidium, Myrtus, Prunus, Mesembryanthemum, Spiraea, Rosa, Rubus, Potentilla
Class 13 - Polyandria (Numerous Stamens): Papaver, Sarracenia, Clusia, Bombax, Bixa, Mimosa, Cistus, Delphinium, Nigella, Magnolia, Annona, Anemone, Ranunculus
Class 14 - Didynamia (Four Stamens in two pairs of different lengths): Ajuga, Teucrium, Nepeta, Lavandula, Stachys, Phlomis, Dracocephalum, Ocimum, Scutellaria, Pedicularis, Antirrhinum, Scrophularia, Digitalis, Bignonia, Lantana, Duranta, Acanthus, Vitex
Class 15 - Tetradynamia (Six stamens, two shorter than the other four): Draba, Iberis, Alyssum, Cardamine, Cheiranthus, Arabis, Brassica, Cleome
Class 16 - Monadelphia (Stamens bound together by their filaments): Hermannia, Geranium, Sida, Althea, Alcea, Malva, Gossypium, Hibiscus, Stewartia, Camellia
Class 17 - Diadelphia (Stamens bound by filaments, but into two bundles or sheaths): Fumaria, Polygala, Genista, Robinia, Pisum, Lathyrus, Vicia, Clitoria, Glycine, Astragalus, Trifolium, Lotus, Medicago
Class 18 - Polydelphia (Stamens bound by filaments into five bundles): Theobroma, Citrus, Hypericum
Class 19 - Syngenesia (Stamens united at the anthers): Tragopogon, Sonchus, Lactuca, Carduus, Eupatorium, Ageratum, Santolina, Artemisia, Gnaphalium, Erigeron, Senecio, Solidago, Inula, Achillea, Chrysanthemum, Helianthus, Rudbeckia, Centauria, Calendula, Osteospermum, Lobelia, Viola, Impatiens
Class 20 - Gynandria (Feminine males, Stamen combined with style and stigma): Orchis, Cypripedium, Epidendrum, Sisyrinchium, Nepenthes, Passiflora, Aristolochia, Pistia, Grewia, Arum, Arum, Dracontium, Calla, Pothos
Class 21 - Monoecia (Monoecious plants): Callitriche, Lemna, Typha, Carex, Ambrosia, Amaranthus, Quercus, Fagus, Platanus, Liquidambar, Pinus, Cupressus, Acalypha, Jatropha, Ricinus, Sterculia, Cucurbita
Class 22 - Dioecia (Dioecious plants): Najas, Salix, Myrica, Spinacia, Cannabis, Humulus, Smilax, Dioscorea, Populus, Carica, Juniperus, Taxus, Ruscus
Class 23 - Polygamia: Musa, Celtis, Andropogon, Acer, Begonia, Fraxinus, Diospyros, Nyssa, Panax, Ficus
Class 24 - Cryptogamia (Flowers not readily visible): Equisetum, Ophioglossum, Osmunda, Pteris, Blechnum, Asplenium, Polypodium, Adiantum, Lycopodium, Sphagnum, Polytrichum, Mnium, Bryum, Marchantia, Riccia, Anthoceros, Lichen, Ulva, Agaricus, Peziza

Wow! If you take a few minutes to read through the groupings, it is clear the system creates a lot of curious combinations. Many things work pretty well; the orchids are together, so are the mustards. The daisies (composites) are together, but they fall out, along with the lobelias, in their own funny group - plants that have stamens united at the anther. Since all of the composites have five stamens, they could have been placed in Pentandria, but almost certainly Linnaeus enjoyed this clever method of separating them from other plants that do not produce flowers in heads. It is also interesting that Linnaeus groups the gymnosperms in with the flowering plants; pines are right after the oaks. And he includes Ilex in Tetrandia, even though the other dioecious plants are in Dioecia. Clearly, Linnaeus took the license to split whatever hairs he needed to split to make things work out; the system was not without ambiguity.

But what a hoot. Just as an aspiring artist might paint in a gallery, copying a great master in order to discover the techniques involved in creating miraculous effects, we can use Linnaeus's system in order to step into his mind. It is a very orderly, personality-ridden place.

Law and Order in the Plant World

Today is the 302nd anniversary of Linnaeus's birth. His is a curious legacy - revered and derided - remembered and forgotten - contemporary and anachronistic. Most of today's botanists regard him as a towering fossil; we know his L. marks thousands of plant names as part of the Linnaean foundation on which all modern plant names are based. We also know that many modern botanists are annoyed by the linearity, order, and equivalence implied in this genus-species system we inherit. Evolution has not been so complicit with human attempts to pigeon-hole the whole of creation; as Harold Bold often said: "Nature mocks at human categories."

And it was categorization that Linnaeus was all about. Today's significant holdover from Linnaeus's work is his consolidation of the binomial system of nomenclature. Linnaeus systematically brought every available plant into compliance with his way of naming and categorizing. The simplicity and thoroughness with which Linnaeus applied his way of naming plants proved of immediate and international value, sweeping away the awkward and forgetable. Today, through international agreement, we base the Code of Botanical Nomenclature on his 1753 Species Plantarum.

But for Linnaeus's contemporaries, most of whom idolized him, the immediate value of his publications was the way he organized plants. Linnaeus created a straight-forward method of grouping plants, a system that was easily memorized and utilized. For the first time in plant studies, anyone could study a new plant and know where to file it away - that is, how to classify the plant.

As a young man, Linnaeus had fallen as a thrall of sex, or more accurately, he was among the first generation of botanists who came to study plants with the awareness that seed are the fallout of sexual reproduction. Only a few years before his birth had it been made clear that pollen is the male generative force, analagous to human sperm. Linnaeaus took that fresh concept and ran with it. It was obvious to him that reproduction was crucial to preservation of every species, and the salient characteristics of reproductive organs should be directly correlated with the definition or nature of each different species. The result was his sexual system of classifying plants. Plant genera (and therefore the included species) could be grouped into Classes based on numbers and character of stamens, and within the Classes, into Orders based on the numbers and characteristics of pistils or further information on stamens.

The popularity of the sexual system of classifying plants was short-lived however. Within just a few years of Linnaeus's death, botanists published systems that grouped genera into families that seemed more "natural" - families that reflected the natural affinities of different groups of plants - affinities that would be considered ancestral and evolutionary a century later. So we are left with the binomial system of nomenclature as the residual legacy of Linnaeus's work.

But not so fast. In celebration of Linnaeus's 300th birthday two years ago, I decided it would be fun to attempt organizing a few salons that replicated the experience people would have had with Linnaeus's methods. I pulled out his simple system, assembled groups of people, and worked with the students through many plant samples. What a revelation. Of course there was no way we discovered that Linnaeus's sexual system has anything to say about how plants should be grouped or classified. What we did learn was how quickly his system cut through the mystery of a new plant. No wonder Linnaeus loved his method. He studied thousands of different kinds of plants; the sexual system represents the life-experience of one of the most brilliant field-botanists who ever lived. In using the sexual system to guide our study of many different plants at a single setting, we stepped right into Linnaeus's times and challenges. His system worked, quickly and intelligibly. It proved to be a great teaching method, bringing novices quickly into an appreciation of plant structure and diversity. Working through flowers from Linnaeus's perspective is wonderfully enlightening, engaging, and worthwhile.

But that doesn't mean there are publishable results. The system has serious limits. It gets you to a place in a list or chart, but it doesn't reckon on today's reality - the sheer number of different kinds of plants we have come to understand there are and have been on Earth. Linnaeus's system suggests a matrix of potential structural combinations, which would mean our discovery of plants would have yielded less than 50,000 kinds. He thought all the world's plants would be known in short order. That did not happen, and with over 250,000 accepted species, we continue to add new kinds. And, honestly, there is nothing that Linnaeus's system brings to the table in a contemporary understanding of plant affinities or evolution.

But for students who want to learn more plants, and more about plants, Linnaeus's methods have much to offer. Following his system gives the student of plants access to Linnaeus's approach to making sense of the great range of plant diversity - an approach molded through experience and a genius for comprehending and organizing the breadth of creation.

She Loves Me, She Loves Me Not

The season is full of Daisies - which botanists call Composites. And these "flowers" are indeed composed..., each daisy is a head of flowers (a particular kind of inflorescence) made up and masquerading as a single flower. When you pull out, petal by petal, the parts of a daisy as you alternate between being loved or not, you are not simply pulling single petals from a flower. You are tugging individual flowers (little flowers called florets) from a cluster that looks, for all the world, like a single flower.

If you break a daisy flower apart, the florets will stand out more clearly. In many cases, when the heads are classically daisy-like, you will actually discover the head is made of two kinds of flowers. Each of the prognosticating petals that wants to be pulled out comes from a single flower - which we call a ray, because it radiates from the head. There are other even more minute flowers that fill the center of the head, which we call the disk florets. These florets are more symmetrical, each one showing five little angular lobes that represent individual petals that make up the corolla. If you turn your attention back to the rays, you may see little teeth at the tip of a petals, teeth that reflect the same lobes seen in the disk flowers.

The base of each floret is the part that becomes the fruit, so it is the ovary. Since it develops below where the other flower parts emerge, we say this is an "inferior" ovary. All daisies have inferior ovaries. Each one matures into a dry, hard one-seeded fruit, which botanists call a nutlet. So what nutlets do you know. Well you certainly know the Sunflower seed - each one develops inside the inferior fruit of a Sunflower floret. So a Sunflower is, pretty demonstrably, a daisy.

But there are thousands of different kinds of daisies, different kinds of composites. Dahlias, Zinnias, Chrysanthemums, Marigolds, Calendulas, Liatris, Edelweiss, Achillea, and even Lettuce and Artichokes - these are all composites. Most are pretty normal, at least for a daisy, and have both ray and disk flowers. But whole groups of daisies produce heads of florets that are fully of the disk type, and there are other groups that produce heads made only of ray florets. There are even a few, really odd composites, in which the head has a single floret. With the shrubby Coyote Bush (Baccharis), whole plants produce flowers that are either female (no stamens) or male (no pistils.) In these, the heads of flowers on one shrub look entirely different from those on another; the males look very different from the females. So these simple possibilites introduce quite a range of possibilities in biology and appearance.

At times we have seen political movements that propose we make the Sunflower the national flower. I remember a Senator Dirkson who loved Marigolds, and wanted to make the Marigold the US National Flower. If that ever happened, we'd have to call it the National Inflorescence.