Plant of the month (©Pierre Laszlo, all rights reserved)
Sambucus nigra (Caprifoliaceae)
Had one to choose a plant species for its non-discriminatory friendliness, this one, related to the honeysuckle, might get the prize. The host to numerous birds and insects, at various stages of development, it also proved itself repeatedly helpful to mankind. Providing us not only with food and flavor from its fruit, with medication, and even with easily devised musical instruments such as flutes, it has relentlessly supplied us tools to satisfy our scientific curiosity.
This generous friend is the alder (also called alderberry), Sambucus. There are seven species in Europe and North America alone. Others thrive in temperate to subtropical climates in both hemispheres, on nitrogen-rich soils. The alder is as much a feature of the French country, in which every farm, every house has one in its yard, as the pub is to an English village, the basketball hoop outside an American house or the gingko tree in front of a Budhist temple. As a child, I would climb its easily accessible if rather fragile branches. It does not quite qualify as a tree, it is a large bush, about 3-5 m in height.
At the end of spring, the branches bear large clusters of small whitish flowers. Their fetid smell can be offputting, Shakespeare refers to ‟the stinking alder” in Cymbeline. Flowers turn into clusters of small black, blue-black, or red berries. These berries are manna to birds. In Northern California, elderberries are feeding stations for migrating band-tailed pigeons, whose flocks can lay bare an entire shrub in less than an hour. Humans are also fond of the berries, for various beverages such as the Italian Sambuca liqueur, jams and traditional medication for various ailments.
Many insects use alders for their dwellings. For instance, the endangered Valley elderberry longhorn beetle (Desmocerus californicus dimorphus) is found, in the Central Valley of California, on the blue elderberry (Sambucus mexicana). Butterflies feed and dwell on it in the larval stage and they include many species: Angerona prunaria, Apeira syringaria, Chloroclystis v-ata, Choristoneura hebensreitella, Eupithecia tripunctaria, Euproctis chrysorrhoea, Gortyna flavago, Melanchra persicariae, Ourapteryx sambucaria, Phlyctaenia coronata, Saturnia pavonia, Thetidia smaragdaria, Udea olivalis, Udea prunalis, … The list is long indeed. Many other insect families seek and find shelter with the alder.
The alder ought to be known as a gold mine. The tree is worth its weight in gold. I am not referring to its ecological importance, nor to its admittedly limited and rather archaic economic significance. What I have in mind is the alder as purveyor of tools for science. It is now clear that the only hope for survival of the human species on this planet — perhaps also survival of any life on Earth — is to bank on science. Riches from the alder ought to be not only noted, but perhaps even revered.
The alder has benefitted biology in at least two ways. One goes back several centuries, to natural historians whose cleverness and manual dexterity in experimentation are equally wonderful. The other, contemporary, is no less admirable. The first use of the alder I shall mention was devised to help optical microscopy. The second was devised for the age of electron microscopy.
The former solves the problem of how to secure a mote, how to get hold of a mere speck of material to put it under a lens. Tweezers, too big and unwieldy for the purpose, won’t work.
A botanist takes instead a razor blade and a piece of pith from the alder branches, a couple of inches long. This cylinder is split vertically along a diameter. A groove is then cut into one or both of the identical halves, depending on the needed size. The stem of a plant is inserted and held firmly by re-applying the two halves against one another. Having it protrude just a little, one can slice it repeatedly — slices with a thickness of about a quarter of a millimeter, so thin as to be transparent. Upon mounting between a lamella and an object slide, both glass, it is ready for examination under the microscope. I have myself practiced this little routine quite a few times when I audited a class in botany more than half-a-century ago.
The latter application is more recent. One of the most widely used lectin comes from the alder bark. It sells for about US $ 300 per milligram. 100 grams of bark, which any alder bush easily provides, can be turned — easy biochemistry to perform — into about 100 mg of the stuff: make the calculation and you will find that indeed the alder is worth its weight in gold.
A lectin is a protein. It agglutinates red blood cells. It is a valuable tool because it allows laboratory scientists to uniquely characterize individual sugar molecules. To give just one example of the use of the alder bark lectin, it has been applied to flu viruses, their receptors in the body, for instance in the ciliated and glandular epithelium of the respiratory tract, and to study other viruses and pathologic bacteria as well.
The alder was featured in folk tales. Judas Iscariot was said to have hanged himself from an alder, which Shakespeare echoes in Love’s Labour Lost. Another myth was that of the Alder Mother, a spirit to whom one had to pay reverence. The tree could be cut only when requesting her permission, by chanting a rhyme, failing which she would exact revenge. As a lifelong devotee of the elder, such a superstition intrigues me.