Tag Archives: plants

Pycnofibers? Or trichomes?

27 Dec

Pycnofibers and trichomes

Before dinosaurs and birds, other creatures like pterosaurs lived on the Earth. They didn’t have hair or feathers. But they had surface filaments on their bodies that can be seen in their fossils. The cellular structures are called ‘pycnofibers’. They had a single empty cylinder inside each filament. Pycnofibers arose from the epidermal cells, not from under the skin like hairs with their hair follicles. Nor like feathers. 

What amazes me, and which I find amusing, is that plants have these structures, too. They are called ‘trichomes’, and are well documented, including electron micrographs depicting the variety of trichome structures and shapes. Yet, nowhere in the literature that includes ‘pycnofibers’ is any mention of trichomes! Perhaps pycnofibers are the animal equivalent of the plant trichome. 

Trichomes can be inert with no chemical activity, or metabolic. Some are single-celled, some are multi-celled. Some are metabolic, some are secretory. Some are visible with the naked eye, others require a microscope. There is even a ‘trichom-ome’ now; the investigation of all the proteins and pathways involved in producing trichomes and their contents. Yet, the content of some trichomes is only air. And I am pretty sure that some of you have had encounters with trichomes. 

A trichome encounter

Last summer, while conducting a waterfowl breeding survey, I had an intimate


Trichomes on stinging nettle.

encounter with trichomes. The route for the survey was a walk-through on an unmowed dike dividing two marshes. Much of the vegetation – mustards, and other composite plants- was over my head at 5 feet plus four inches. The route was like pushing through jungle vegetation. One hand held my notebook and pencil and the other hand and arm pushed vegetation aside. 

Three-quarters on my way back to the starting point, my left hand and wrist began burning, like dozens of bites by fire ants. When I reached the vehicle, both hand and wrist were burning, red, and itching like crazy. Good thing I always wear long-sleeved shirts.

The culprit was the trichomes on stinging nettle plants. These tiny hair-like structures are on the stems and undersides of leaves. The thin outer portion of the trichome is silica, and it is very brittle. Shaped like a long hair with a fine point, the tip can break off and penetrate the skin of an animal that brushes up against it. When broken, a complex mixture of chemicals inside the trichome is dumped onto and into the skin. 

A chemical analyses reveals that those trichomes contain neurotransmitters: histamines, acetylcholine, and serotonin. Several acids are also in that mix: formic acid (remember my reference to fire ants?), oxalic and tartaric acids. One or more of these compounds can elicit pain or itching. But the cocktail of all those compounds may be the synergy to induce long-lasting pain, itching and inflammation. 

Over the next week, my hand and wrist swelled so much I had trouble moving my fingers and closing my hand into a fist. I had to switch my watch to the right wrist. I usually held my lower arm up, bent from the elbow. If I didn’t, the wrist and hand throbbed in addition to burning and itching. Twice-daily applications of a dermal corticosteroid somewhat alleviated the symptoms, but not enough. Ice also helped, but I couldn’t keep ice on it 24/7. A phone call to urgent care recommended trying an oral anti-histamine and applying a dermal anti-histamine, with icing once every hour if possible. I added a dose of ibuprofen twice a day. The pain subsided before the itching, which was the hardest symptom to  to ignore. 

Why trichomes?

With that anecdote in mind, you may guess the function of some trichomes and why many plants evolved these dermal structures. Not all trichomes are bad, however, Some are merely hair-like, with pigmentation, and cover the leaves. They are inert; no compounds are inside their trichomes. Their functions may be to trap rain and morning dew to cool the surface of the leaves and stems, or to reflect light away from the surface. Many plants in arid climates have these types of trichomes. 

If you do a Google search on ‘trichome’, the most prevalent result is photos of marijuana trichomes. Trichomes on the stems and leaves of hemp plants, including marijuana, are highly evolved deterrents against herbivory by animals. The three different types of trichomes of Cannabis sativa, or marijuana, are “the very factories that produce the hundreds of known cannabinoids, terpenes, and flavonoids” that the plant is known for. Some trichomes -those that look like tall-stalked, bulbous mushrooms- have higher concentrations of the above compounds and cover specific tissues on the plants: the calyx of the flower buds. When crushed, they exude a sticky, odiferous resin that often repulses animals from eating them, except for humans. 

Why did Mesozoic pterosaurs have pycnofibers? Were their pycnofibers the animal version of plant trichomes? Possibly.  A question is, which evolved first? 

A wandering verbena (Desert Verbena)

19 Apr
Glandularia bipinnatifida. Photo courtesy of Pam Gordon.

Glandularia bipinnatifida. Photo courtesy of Pam Gordon.

Folks driving along the desert roads this month may see many small tight masses of purple flowers waving in the breeze. The Desert verbena are at their peak of flowering right now.

Here’s another example of ‘mixed identity’. There are many common names for this plant: Desert verbena, Prairie verbena, Dakota vervain, Davis Mountain mock vervain, and Moradilla. While many common names exist for a particular plant, one can usually rely on a more specific scientific name. Not the case here (again).

Older published widlflower guides list this plant as Verbena wrightii, and a member of the Verbenaceae (or Vervain) family. While our plant of the week is indeed in the Vervain family it’s genus and species names have changed.

Glandularia bipinnatifida close up.

Glandularia bipinnatifida close up.

Back in the early 1800’s, naturalist Asa Gray named the plant for Charles Wright , a teacher, surveyor, and plant collector, known notably with the Mexican Boundary Survey. However, new molecular research tools in the last decade or so have determined that a few members of the Vervain family have different chromosomes (numbers and sequences) in their chloroplasts, the organelles in plants that are the powerhouse for producing energy (photosynthesis).

Scientists discovered that some genetic information has been transferred between members of the Vervain and Glandularia genus. In other words, members of these two genus and species have hybridized not just once, but possibly three times as these plants spread north from South America.

Although several plants were once classified as Verbena, and still resemble many of that genus, they have been reclassified (1979) based on genetic similarities and differences. The most commonly known reclassified member is that which was known as Verbena wrightii, or Desert Verbena. It is now recognized in the botanical literature and more recent wildlfower guides as Glandularia bipinnatifida. Although there are two subspecies of this plant referenced (G. bipinnatifida var. cilia. and G. bipinnatifida var. bipinnatifida), their taxonomic classifications remain invalidated and both will find them used synonymously for this species. Perhaps more chemical and molecular studies will elucidate any differences that may exist.

Meanwhile, if you get close enough and smell these plants you may or may not be enamored of their fragrance. While many members of the Vervain family and Verbena genus have pleasant scents, this one had to sit outside after I gathered some samples yesterday. 🙂

For those interested in a recent review of the latter issue, see the following reference, “Taxonomy of the GLANDULARIA BIPINNATIFIDA group (Verbemaceae) in the USA”, by Guy Nesum (of Forth Worth!) in Phytoneuron, issue 46, 2010.

Springing forwards and backwards

25 Mar

Most deserts are known for their extreme weather, especially temperatures. The northern Chihuahuan desert is no exception. We have had an unusually cold winter with prolonged periods of below-average temperatures. Of course, that parallels the rest of the country as well. However, here we have had temperatures in the 90’s during the day and in the high 30’s at night. Spring usually arrives with a pattern of more consistent temperatures and less extremes. This year, spring continues the vacillating extremes of temperatures. In many cases, new growth on plants have been damaged by repeated bouts of frost after days with high temperatures (high 80’s to near 100 degrees).

Regardless, many flowers are popping and leaves are emerging on trees, shrubs, perennials and even cacti. The yuccas have been sending up their giant flower masses throughout the southern Big Bend area for a few weeks now, and the coveted bluebells carpet many roadside areas. I have been capturing some of the lesser known flowers the last week or so, which also provides me with an opportunity to practice macro-photography. I will post some of those photographs here.

Feather Dalea (Dalea formosa)


Bowl Flax (Linum berlandieri)




Velvety Nerisyrenia or Mesa Greggi (Nerisyrenia camporum)

Fendler’s Bladderpod

4 Mar

One of the first wildflowers to pop up like little yellow stars in southwest Texas is Fendler’s Bladderpod (Physaria fendleri). Starting last week, these tufts of small yellow flowers are marking many of the desert areas like globs of bright jewels.

Here again was an adventure in identification for several reasons. And I will outline how I pursued identifying this plant. Most of the yellow flowers we see with non-fused petals belong to the very large family Asteraceae, or the sunflowers, and have multiple flower petals (more than 4 petals/flower). However, a few yellow flowers have only four or less non-fused petals. Those usually belong to a different family of plants: the Brassicaceae, or mustard family.

Fendler’s Bladderpod

Once the flowers were narrowed down to the family, then one must use details of leaves, seed, and growth habit to correctly identify the plants. This process is called ‘plant systematics’, most commonly referred to in plant guides as ‘keying’ a plant based on their parts. But that also has limitations, as I will explain in a bit.

When the flowers were keyed in the mustard family and in a genus (Lesquerella), sometimes collectively called ‘bladderpods’, the next step was to determine which species this plant was. This was more difficult because the flowers and leaf shape are typical of two species: Gordon’s Bladderpod (L. gordonii )and Fendler’s Bladderpod (L. fendleri). They both have tiny silver hairs on their leaves and stems. And they grow in the same region!

The only differences between these two species are that the Gordon’s Bladderpod is an annual, whereas the Fendler’s Bladderpod is a perennial. Because of that, the Gordon usually begins flowering a month or two later than the Fendler’s. Additionally, the Gordon’s usually have longer stems that may lie on the ground and turn up at the tips, and thus they have a more open appearance. The Fendler’s, on the other hand, often grows in more compact and upright clusters.

The other issue with identification of these plants is in the names. Again, I ran into reclassification of an entire genus of plants where the literature, especially plant guides, is very slow to catch up. Including many online plant databases (even state and federal).

The first specimen of this plant was collected in 1847 from near Santa Fe, NM, by Prussian-born natural historian Augustus Fendler. From the specimen, the plant was named and characterized by the famous botanist Asa Gray as Vesicaria fendleri.  Years later (1888) the curator of the Gray Herbarium (of Harvard University), Sereno Watson, who was appointed by Gray, renamed the plant Lesquerella fendleri.

Now, move ahead in time to 2002 when a team of botanists and biologists petitioned the organizations involved in taxonomical name conventions to move all the plants of the genus Lesquerella to another existing genus, Physaria. Why would they propose that change? Traditionally plants have been categorized and named based on comparative data: morphological, ecological and distribution. However, in the past two decades the addition of more sensitive and technical tools, such as molecular biology and genetics, have been applied to confirm similarities and separate differences. Consequently, some organisms are now determined too similar rather than more different and are reclassified together in the same genus, even species. Conversely, some molecular differences are important enough to separate some species that were once classified together.

When in doubt, I have always turned to a database used by nearly all biology, molecular and genetic scientists, and which is continually updated, sometimes more than daily. It is crucial for all scientists to keep up with changes in scientific data and reporting, which truly reflects the dynamic world of life sciences and discovery. Although many of the media and even federal plant databases still use the old naming convention, the genus Lesquerella  is no longer accepted or correct.  As of now most of the species within that genus are now included in the official genus name, Physaria. Unfortunately, it may take another five or more years for that name to propagate through all the databases and into the literature, including the nature guides everyone uses for identifying plants.

An ending note about these two bladderpods: they can be poisonous to livestock, especially horses. The seeds especially contain a large amount of oil that can be toxic if eaten in excess. On the other hand, the Fendler’s Bladderpod is now being considered as a commercial source of oil to make plastics, grease and as an ingredient in cosmetics, mostly to replace castor oil. Me, I just like enjoying their little yellow mounds of stars on the desert floor.

Fendler’s Bladderpod

Texas Persimmon

17 Feb

Texas Persimmon (Diospyros texans)

214_2585-2A common wild shrub in the Texas hill country and Trans-Pecos area, it is also known as Mexican Persimmon and Black Persimmon. Shrubs can grow up to 25 feet high with attractive curving branches. An easily identifiable trait is the smooth gray bark that sometimes peels off in sheets on older wood, revealing pinkish and beige wood underneath. The leathery dark green leaves can be evergreen (persistent) depending on local climate. I saw shrubs in Lajitas in full leaf early February, but nearly all leaves had fallen off shrubs at the Terlingua Ranch Lodge area.

Small white flowers appear February-June, with male and female flowers on different plants. Accordingly, fruits form on only female plants. Small (1” diameter) seeded and juicy black berries ripen in mid-summer. The berries are eaten by many bird species and mammals, including turkey, coyote, javelina, raccoon. White-tailed deer eats leaves and fruit. The dense branches are also favored by birds for building nests, as indicated by a shrub growing close to where I am now.

When ripe, the fruits are edible with a sweet and sour taste. Black juice stains fingers and fibers. Fruits were used as an astringent for treating sores in the throat and mouth, and the bark was chewed to treat heartburn. Also, local accounts praise persimmon jelly and wine.

The Texas persimmon is a favored landscape tree with aesthetic qualities accompanying its wildlife and food attributes. Young trees are slow growing and like partial shade with abundant water. Conversely, established plants tolerate full sun and limited water. Dried fresh seeds may germinate, but the plant is difficult to propagate by cuttings. This shrub is a perfect candidate for xeriscaping in semi-arid and arid environments and makes its home quite well here in the Big Bend region.


‘I’m too thorny for my leaves….’

28 Jan

Allthorn (Koeberlinia spinosa)

Another plant of many common names is one that sticks out like a sore thumb. Literally.

Found mostly in the Chihuahuan Desert area of Texas, New Mexico and Mexico, the Allthorn seems to diverge from many common assumptions. Although known by several common names –Crown of Thorns, the Crucifixion thorn, Junco, and Allthorn- this thorny shrub, Koeberlinia spinosa, won’t be confused with any other once encountered.

Allthorn (Koeberlinia spinosa) Winter, 2014.

Taxonomists also seemed baffled by this perennial shrub. The althorn plant stands alone: it is the only species in its genus (Koeberlinia), which is the only genus in the entire family, Koeberliniaceae (Allthorn, or Junco, Family).

Typically growing up to 10 feet or more and with many branches going in all directions, its most noteworthy character is the long, thick and dark green spines.  What most people don’t realize, however, is those sharp spines are actually stems.  Tiny and scale-like Allthorn leaves appear shortly after a rain on the spiny stems and dropping off within a few days after rains cease.  Likewise, the small greenish-white flowers appearing in March through October, also in response to rains, grow in inconspicuous clusters. The one-quarter inch shiny black berries, on the other hand, are obvious against the dark green stems and favored by birds, although some herbivores may feed on very young stems.

Allthorn stems

Allthorn stems

The Allthorn is similar in some respect to the well-known ocotillo, the tall whip-like thorny stems growing from a single base at the ground. Both shrubs are perfect examples of adaptation to the desert environment: they leaf out in response to moisture in the air and drop their leaves shortly thereafter. Additionally, they are somewhat an oddity in the plant physiology world. Although both shrubs have transient small leaves, their green bark and stems contribute to their food supply by a rather unique ‘hybrid’ of two photosynthetic pathways. Although this process is less efficient for food production, it does reduce water loss by transpiration, which is higher in leaves than in the plants’ green stems.

In contrast to the ocotillo, which has shallow roots, the Allthorn has an additional survival mechanism: its roots reach into the soil both at shallow and deep levels to reach water. Older wood turns woody and dark brownish gray, which helps protect the trunk of the shrub, and the branches tangle and twist to form an impenetrable barrier to humans and animals alike.

The Allthorn is very drought and cold hardy, surviving temperatures to 0 degrees F, and prefers full sun. Specimens of this shrub were first found and characterized by a German naturalist, Wilhelm Freiberr Karwinsky, in Mexico around 1830. The plant, including family and genus, was named in the honor of a German clergyman and botanist C.L. Koeberlin, by Karwinsky.

Allthorn shrub in winter.

Chihuahuan Desert Plant Survey

10 Dec

Agave harardianaThis year I officially (to me) began a personal survey of plants in the Chihuahuan Desert. Some of my collection has been uploaded to Project Noah where a Mission (Chihuahuan Desert Plant Survey) has been created specifically for this project. Contributions and participation are welcomed.This is an ongoing project and more spottings will be uploaded to Project Noah as time allows.

In addition, summarized spottings will be entered on a page in a new sub-category after I determine the best way to accommodate the data. I need to research options on the WordPress website. When this is accomplished, I will post a notice here.

Meanwhile, here is my favorite: Agave havardiana, often called Big Bend Century Plant. This was found and photographed in the Chisos Mnts. in BB National Park. (I call it ‘Blue Dolphin.’ )

%d bloggers like this: