Monday, December 28, 2020

Where does the corn go? The answer maize surprise you!


I probably have to apologize for that pun, but I do like sweet corn (which is more accurately called maize, and whose scientific name is Zea mays). It makes for a good snack, and of course I love some of the other foods where maize is a major component, such as corn tortilla.

But it should come as no surprise to people that unlike rice, which directly feeds several billion souls, the vast majority of the maize crop does NOT go into directly feeding people. In fact, when I looked it up, I was surprised to find out that only a very small percentage of whole maize makes it to the table.

The largest use of maize is for feeding animals (around 40%), and right behind it is its use as biofuel (around 30%). Less than 10% of the total crop goes to either food or drink in the USA, and even the majority of that ends up as high fructose corn syrup. Unfortunately, very little of that crop goes to making the sweet juicy snack that I love.

For a detailed and interesting look at how this very important grass species impacts the country, I highly recommend watching the documentary King Corn, which is available in its full length below.

Enjoy and learn!

Sunday, December 27, 2020

Sound the alarm! Miscanthus hoodlums escaping!

There is no doubt that the exotic species Miscanthus sinensis (Chinese silvergrass) is very heavily used in commercial and residential landscaping. I see them everywhere nowadays, from mall parking lots, office lots, to the front yards of suburban homes. Even arboretums like the Frelinghuysen Arboretum  in Morristown,  New Jersey use it extensively due to its beautiful form and flowers. But at least until recently, I have not seen "escaped" specimens that have jumped the fence here in New Jersey and made its way into the wild.

M. sinensis behind Panicum virgatum and Pennisetum sp, and Festuca glauca (Frelinghuysen Arboretum)

This changed when I visited the South Mountain Recreation Complex in Essex County, which featured a huge reservoir surrounded by a paved path. People can walk or run around the lake using this path, and trails peel off from it to go into the deeper woodland hiking paths.

All along the perimeter of this path are planted shrubbery as well as ornamental grasses, and one of the species used was of course M. sinensis. I was able to tell it was this because even though all the grasses had been cut to the ground for the winter, I still spotted some of the distinctive inflorescence spikes of this species lying nearby.

Escaped M. sinensis along side of woods
Imagine my surprise when we left the main path and crossed a hilly outcrop to intersect a hiking path entrance, only to see uncut but dried clumps of M. sinensis growing along the woodland edges! There was one main cluster perhaps 4 meters away from some of the cut ornamentals, but there were also secondary clusters and individuals farther away and enmeshed in the native undergrowth.
Escaped M. sinensis in the undergrowth

Fortunately, unlike some other invasive grasses, rhizome expansion in this species is not as aggressive, but it still is somewhat of a concern that this particular population is showing signs of expansion into the nature trails. Time will only tell if this burgeoning invasion will create significant problems in the future.

Friday, December 18, 2020

How one badass grass thrives at the thermal limits of eukaryotic life

It's not an exaggeration to say grasses as a family have adapted amazingly well to most habitats on earth. But there is at least one species that takes that adaptability to new levels.

Living in the active geothermal areas of Yellowstone National Park takes some major adaptations. It is an extreme and hostile environment with rhizosphere temperatures exceeding 40°C. Many proteins denature above 41°C, and in people a body temperature at 43°C or above normally results in death or at the least serious brain damage and cardio-respiratory collapse.

In such an extreme environment, there are only nine vascular plants that have managed to successfully colonize this habitat. Chief among them are the grasses, which are both the most prevalent and most heat-resistant species in the area. But the award for the most extreme plant goes to Dichanthelium thermale (formerly a subspecies of D. lanuginosum) , which was flourishing in soils with an average of 44° C and a recorded maximum of 57°C! (Stout and Al-Niemi, 2002)

(c) James St. John, Wikipedia
When researchers studied D. thermale, they found that it was even more amazing than they initially thought. This grass species had little problem living at the absolutely mind boggling temperature of 65°C for days on end, and they discovered that this ability was the result of a symbiosis with a new endophytic species of the fungal genus Curvularia (Redman et al, 2002).

Curvularia protuberata was found in the roots, leaves, crowns, and seed coats of D. thermale, and neither the grass nor the endophyte could survive on its own above 38°C. But when endophyte-free grass was inoculated with the fungus, it regained its remarkable thermotolerance.

The researchers surmised that this protection from heat could be the result of several possible mechanisms. One possibility is that the fungal endophyte produces cell wall melanin that may dissipate heat along the hyphae and/or complex with oxygen radicals generated during heat stress. Another possibility is that the endophyte may act as a “biological trigger” that allows the symbiotic D. thermale to activate stress response systems more rapidly and strongly than non-symbiotic plants.

Redman et al, 2002

The symbiosis became even more complex when researchers announced that they had found a third party in the relationship several years later. It turns out that the fungal endophyte was infected with a double stranded RNA virus, and that its ability to confer thermotolerance on D. thermale was dependent on this infection!

Endophyte-free D. thermale that was inoculated with the fungus+virus survived in heated environments, whereas endophyte-free D.thermale  inoculated with the fungus without the virus did not survive in the same environment (Márquez et al, 2007).

Márquez et al, 2007

The unraveling of this complex symbiotic relationship could even have applications in agriculture. When tomato plants were inoculated with the wild-type fungus C. protuberata, their tolerance to heat was improved, albeit only slightly, indicating that the mechanism behind this thermotolerance may be conserved among many different plants.

But this potential novel application in the future would not have been thinkable if it were not for the humble D. thermale in Yellowstone and other geothermal parks. So as we marvel with awe at such an intricate and beautiful example of symbiosis, be sure to also give a respectful nod at this one badass thermotolerant grass and its fungal and viral partners!
Modified from Marin et al (2020), te Velthuis (2014), and J. St, John (Wikipedia)

Literature Cited

Marin, Yasmina & Hernández-Restrepo, Margarita & Crous, Pedro. (2020). Multi-locus phylogeny of the genus Curvularia and description of ten new species. Mycological Progress. 19. 559–588. 10.1007/s11557-020-01576-6.

Márquez LM, Redman RS, Rodriguez RJ, Roossinck MJ. A virus in a fungus in a plant: three-way symbiosis required for thermal tolerance. Science. 2007 Jan 26;315(5811):513-5. doi: 10.1126/science.1136237. Erratum in: Science. 2007 Apr 13;316(5822):201. PMID: 17255511.

Redman RS, Sheehan KB, Stout RG, Rodriguez RJ, Henson JM. Thermotolerance generated by plant/fungal symbiosis. Science. 2002 Nov 22;298(5598):1581. doi: 10.1126/science.1072191. PMID: 12446900.

Stout RG, Al-Niemi TS. Heat-tolerant flowering plants of active geothermal areas in Yellowstone National Park. Ann Bot. 2002 Aug;90(2):259-67. doi: 10.1093/aob/mcf174. PMID: 12197524; PMCID: PMC4240417.

te Velthuis, A.J.W. Common and unique features of viral RNA-dependent polymerases. Cell. Mol. Life Sci. 71, 4403–4420 (2014).

Saturday, December 12, 2020

Winter Beauty: Ornamental Grasses!

Panicum virgatum, Schizachyrium scoparium, Calamagrostis sp, Panicum virgatum 

You can find beauty in the most mundane of surroundings.

Deep Cut Gardens in Middletown, NJ features a gorgeous formal garden, tropical and other interesting plants in greenhouses, and short trails for nature lovers. 

But hidden in plain sight in the main parking lot was something that actually made me gasp.

There between the rows of parking spaces and parked cars stood masses of ornamental grasses, their now-dried stems and leaves rising tall and straight towards the cold November sky. Every single island in the lot was filled with these botanical wonders.

The great thing about it was that these were not the non-native Miscanthus sinensis cultivars that are so beloved nowadays by landscape designers, but mostly native perennial grasses.

The tallest were Panicum virgatum cultivars (switch grass), their erect forms standing like disciplined soldiers ready for battle.

P. virgatum
Between stood reddish-hued Schizachyrium scoparium (little bluestem),  another hold-over from the vast prairies of olden America, plus short groupings of what I took to be an elegant Calamagrostis cultivar.
S. scoparium

And for lovers of Miscanthus sinensis, the park had a huge specimen towering over a small decorative pond just steps away from the entrance.

M. sinensis across the pond from the cattails
I love that there has been this strong shift in the landscaping business towards using ornamental grasses as part of their designs. I mean, with their dynamic forms and dramatic color changes over the course of the seasons, such grasses beat boring shrubbery all the time! ;-)

P. virgatum with dried airy panicles still in place

Sunday, December 6, 2020

Calling all orchid-wannabees: Where are the epiphytic grasses???

I was doing a hike at one of the NJ parks a week or so back when I happened to see a grass that was growing from between the branched fork of a now leafless tree.

The grass looked quite happy and healthy, and a quick look at its base showed some accumulated debris, and perhaps even soil. I can only surmise that it got to its present location via a wind blown seed being deposited in between the trunks.

This of course made me wonder why there didn't seem to be any obligate epiphytic grasses.

Epiphytes are plants that spend part of their lives growing on other plants. They use their host for support but do not depend on them for nutrition or water (unlike parasites), and the main reason for becoming an epiphyte in forested areas is somewhat obvious. By growing high up (perhaps even all the way to the top of the canopy), the plant will have access to light that it would not have growing in the soil. 

But the environment for such adventurous species is not a benign one, with the lack of access to soil nutrients and water being the main reasons why not all plants have evolved to take advantage of this lifestyle. Those that did have a variety of morphological and physiological adaptations that allow them to flourish far above the dark forest floor. For example, some orchids have fat pseudobulbs and tubers where they store water and carbohydrates in anticipation of the periodic times when the environment dries out. Their roots are also highly modified so they are able to hold tightly onto trunks and absorb moisture very rapidly using a sponge-like layer called the velamen.  

Epiphytes. (c) Hans Hillewaert - Wikipedia
Even with all these obstacles, a lot of species have made the leap to an epiphytic lifestyle. Epiphytes are not exactly rare, with about 10% of all vascular plants being epiphytic, and with the majority of cases being in the wet tropics. More than 70% of all orchids for example are epiphytic (Atwood JT, 1986), and so are more than 50% of bromeliads (Zotz, 2013).

The Poaceae number more than 11,000 species, and so when I first tried to find examples of epiphytic grasses, I expected quite a number to be living la vida loca, so to speak, high up above where the lighting is good. Instead, the literature turned up...

...a grand total of ONE (perhaps TWO) species of grasses that have been declared epiphytes!

Tripogon capillatus (c) GBIF, specimen from University of Michigan
Tripogon capillatus grows as epiphytes on the basal parts of tree trunks in humid evergreen forest, and thus has the distinction of being one of that rarest of grasses - an epiphyte! It is part of a group that seems primed for the epiphytic lifestyle. Tripogon is a small genus with only around 50 species, and many of its members prefer to grow on cliffs of moist rocks, wet granitic boulders and rocky slopes, while others can live in xeric to dry habitats (Thoiba and Pradeep, 2020). Some of the species in that genus are even so-called Resurrection plants - able to revive after being completely dried out! 

A second possible grass epiphyte is Axonopus compressus, which was discovered as isolated individuals (n=3) in the lower and middle layers of two trees in Nigeria (Obalum, 2018). But neither species is beholden completely to this tree-living lifestyle. They are instead likely facultative (or accidental) epiphytes, and able to grow in many types of environment. 

So why aren't there more epiphytic grasses? 

Why is a family that is more widespread than any other plant family - one that has members that exist in the coldest, the driest, the hottest, the highest environments - why hasn't it evolved a plethora of tree-living, canopy-dwelling species?

I've been thinking about this, and I think it all boils down to the fact that all grasses are primarily wind-pollinated. It turns out wind pollination is generally uncommon in the wet humid forests where epiphytes are mostly found, and according to at least one source, there have been no reports of any epiphyte that sheds wind-borne pollen (Lowman and Rinker, 2004).

But who really knows? Perhaps there is some other explanation(s) as to why what many consider the most ecologically successful plant family in the world cannot seem to also conquer the tree canopies. 

Literature Cited


Lowman, M.D. & Rinker, H. Bruce. (2004). Forest Canopies: Second Edition. 

Obalum, Sunday (2018). Diversity and spatial distribution of epiphytic flora associated with four tree species of partially disturbed ecosystem in tropical rainforest zone. Agro-Science v17: 46-53

Thoiba, K  and Pradeep, AK (). A revision of Tripogon (Poaceae: Chloridoideae) in India. Rheedea - Journal of the Indian Association for Angiosperm Taxonomy. Vol. 30(2): 270–277
Zotz, Gerhard (2013). The systematic distribution of vascular epiphytes – a critical update. Botanical Journal of the Linnean Society 171(3):453-481

Saturday, November 28, 2020

Feed me! A carnivorous grass?

Grasses get their carbon from the air, transforming it into carbohydrates via photosynthesis. But grasses need other elements too, including nitrogen. Unfortunately, the nitrogen in the air is in a form that is too tightly bonded to be harvested directly, and so grasses get this element from nitrogen compounds that are the by-products of decomposition in the soil, or via nitrogen fixing bacteria (such as those in legumes). But what happens if you live in nitrogen poor soils?  

Carnivorous plants are not the norm in plants, and have mostly been restricted to species that live in nitrogen poor environments and cannot get their N requirements the old fashioned (and less energy intensive) way, by absorption of N compounds through the soil or N-fixing bacteria. Instead, such plants kill and eat animals to get this essential element from their victims.

The fascination with such carnivorous plants as Nepenthes and Dionaea made me wonder whether some grasses have made the leap to carnivory, at least to supplement their normal nitrogen intake. 

Incredibly enough, there is some evidence that some grasses have made the leap to utilizing N from animal sources, albeit indirectly, through partnerships with endophytic fungi. The way they do this is simple and quite interesting, and involves fungi that kill insects in the soil. Such fungi bore thorough the insect cuticle, proliferate within, and ultimately kill it.

Roach killed by Metarhizium fungi. By Chengshu Wang and Yuxian Xia - PLoS Genetics, January 2011
One type of fungi in the genus Metarhizium (M. robertsii) is also an endophyte of the grass Panicum virgatum (switch grass), one of the native species in the old prairies of North America. It lives within the plant roots and in fact is usually found clustered in space close to such grasses. 

Researchers found that P. virgatum root hairs proliferated in the presence of this fungus (Sasan and Bidochka, 2012), and that amazingly enough, the grass "feeds" its fungal boarders carbon photosynthate (Behie et al, 2017).

In return, the grass gets a significant amount of nitrogen from the insects killed by the fungus! 

Researchers tagged test insects with the stable radioactive isotope N-15, and these insects were then exposed to M. robertsii associated with the roots of P. virgatum plants. The researchers discovered that after about a month, up to 48% of the nitrogen in the grass was directly derived from the killed insects, an astonishing percentage that points to the importance of this symbiotic relationship (Behie et al, 2012).

So, there may not be real carnivorous grasses (yet!), but thanks to symbiotic relationships, some grasses get the same positive benefits of killing animals anyways ;-)

Literature Cited

Behie, S., Moreira, C., Sementchoukova, I. et al. Carbon translocation from a plant to an insect-pathogenic endophytic fungus. Nat Commun 8, 14245 (2017).

Behie SW, Zelisko PM, Bidochka MJ. Endophytic insect-parasitic fungi translocate nitrogen directly from insects to plants. Science. 2012 Jun 22;336(6088):1576-7. doi: 10.1126/science.1222289. PMID: 22723421.

Sasan RK, Bidochka MJ. The insect-pathogenic fungus Metarhizium robertsii (Clavicipitaceae) is also an endophyte that stimulates plant root development. Am J Bot. 2012 Jan;99(1):101-7. doi: 10.3732/ajb.1100136. Epub 2011 Dec 14. 

Saturday, November 21, 2020

What determines the maximum height of bamboos?

Bamboos are by far the tallest grasses, with the species Dendrocalamus giganteus capable of growing up to 50 m tall. By comparison, the other grass subfamilies can only boast of species like Arundo donax, which tops out at around 6 m tall.

So how do bamboos accomplish this feat?

Researchers have found that the maximum height of tall plants is limited by the ability of the plant to pull water up from the ground to supply the highest leaves. The water column is drawn through xylem vessels, which are the specialized tubes that transport water in plants. When the cost of supplying water to the leaves is higher than the photosynthetic benefits given by those top leaves, then the plant ceases to grow taller. 

Arundo donax in New Mexico

But that's not the entire story.

In addition to gravity, tall plants also have to deal with cavitation, which involves air bubbles forming in the xylem vessels and preventing the water from being drawn up. The formation of such embolisms is a daily occurrence, and can have fatal consequences when the problem is not fixed. In dicot trees which can grow larger in diameter, one solution is for the tree to simply produce more xylem as old ones become non-functional.

But bamboos cannot produce new xylem to replace older ones that have been filled with air bubbles, so researchers tried to determine how bamboos solve this problem of cavitation, which would be a serious limitation on how tall they can grow.

What they found out was something surprising.

They discovered that bamboos repair any embolisms that occur during the day by closing their stomata at night then using  pressure generated from their roots to dissolve the air bubbles back into solution! The root pressure is generated by actively pumping ions and causing water to flow into the roots as it follows an osmotic gradient.

Even more surprising, they tested 59 species of bamboos and measured the heights of the grasses as a function of their basal root pressures, and they found out that  there was a strong correlation between the two values. The higher the root pressure generated, the taller the bamboo.

So it seems that in bamboos at least, the maximum height of each species is directly related to the ability of that species to generate higher root pressure! The greater the ability of the species to generate high root pressure, the higher its potential maximum height.


Cao KF, Yang SJ, Zhang YJ, Brodribb TJ. The maximum height of grasses is determined by roots. Ecol Lett. 2012 Jul;15(7):666-72. doi: 10.1111/j.1461-0248.2012.01783.x. Epub 2012 Apr 11. PMID: 22489611.

Thursday, November 5, 2020

The beauty of grass flowers

Pennisetum setaceum

Grasses have almost always been relegated to the bottom of the pack when people marvel over the beauty of a plant's flowers, or the magnificence of its leaves. Indeed, many botanical blogs and youtube videos seem to gloss over the presence of members of this most important plant family. In one particular video, the host focused exclusively over some minor forbs, while all around him the gorgeous reddish hued stems of Schizachyrium scoparium waved in the gentle breeze!

Schizachyrium scoparium (Little Bluestem)

This is mostly because the inflorescence of grasses have no sepals or petals, and the flowers themselves are mostly minute and specialized for wind pollination. They are thus easy to ignore in the presence of plants with much larger flowers or large complex leaves.

Schizachyrium scoparium (Little Bluestem)

Nevertheless, many grasses are simply stunning when someone takes the time to really appreciate their beauty through the lens of a camera. Examples of this hidden beauty can be seen in some of the macro shots I have taken of the inflorescence of various grasses.  

Chasmanthium latifolium (Northern Sea Oats)

Witness the purple-hued Pennisetum setaceum, or the gorgeously attired spikelets of Schizachyrium scoparium, whose reddish anthers and stigma dangle from tightly closed glumes. 

Hordeum jubatum (Foxtail Barley)

Or stare in astonishment at the purplish inflorescence of Hordeum jubatum, which looks like the tail of some fanciful faerie tale creature, while the attractive white flowers of Phalaris arundinacea welcomes the visits of enthusiastic hoverflies

Phalaris arundinacea

And what can anyone do but marvel at the strange spikelets of Calamagrostis acutiflora, which look like futuristic streamlined spaceships! ;-)

Calamagrostis acutiflora

Friday, October 23, 2020

Why does maize (corn) feature so much in people's nightmares?

A nightmarish visage

They stand like dark sentinels, their leathery surfaces wrinkled and tough, the corn cobs peering out from behind thick leaves like grotesque mutants. It's almost Halloween, and as expected I see a lot of gardening stores and Farmer's Markets selling dried maize plants. 

If you've never seen such merchandize, then let me assure you they sometimes really do look creepy, and quite a fitting decoration for a tradition that was once a Celtic celebration to ward off ghosts.

Halloween sentinels

But why does corn feature so prominently in horror stories and movies, and in the nightmares of people? Witness for example, Stephen King's classic story "Children of the Corn", or movies like "Husk" and "Night of the Scarecrow." Is there something about this species that inspires such fear and sometimes revulsion?

I think it has to do more with cornfields, than the actual plant itself. There is just something slightly frightening about seeing endless rows of identical maize plants. They rise above you when you walk into them, enclosing you in a moist claustrophobic environment where your imagination can be pushed into thinking about some unpleasant possibilities.

Could you get lost in such a maze, perhaps fated to wander forever within its green bosom? And what are those sinister sounds that you hear, the faint susurrations, the whispers of the corn as the wind caresses their ripe and decaying bodies? What slavering monsters, both human and unhuman, lurk behind the next towering stalk?

Sunday, October 18, 2020

A row of Pennisetum!


Image: Courtesy of 刘伟

I am not especially enamored of Pennisetum, but no one can deny that the flowerheads of these grasses are usually very pretty, which makes it a favorite ornamental.

Here 刘伟 lines up quite a few samples for our delectation (from left to right):

Pennisetum macrourum, P. setaceum 'rubrum', P. setaceum ‘Rueppelii’, P. orientale 'Tall', P. alopecuroides 'Purple', P. alopecuroides ‘Viridescens’, P. alopecuroides 'Hamelin'

Beauty in an arid and darkening landscape: Oryzopsis hymenoides in New Mexico

During our trip to New Mexico in Fall 2019, we visited White Sands National Monument, and one of the notable species we noticed among the few other plants that dotted the stark landscape was Oryzopsis hymenoides (synonym Achnatherum hymenoides), whose common names include Indian ricegrass and sand rice grass.

While traveling later after a visit to Bandelier National Monument, we stopped to view some scenery at a small hilltop. While the wife went off to find a nice viewpoint, I wandered around in wonder at the dried whitish grasses that stood like ancient sentinels on top of the small hill.

One grass in particular looked fantastic in the light of dusk, and with the help of L. Pilkington in a grass identification group, I determined that it was indeed my old friend from White Sands.

This C3 perennial bunchgrass is a native to the area, and can survive in quite a range of environments, from desert to pine forests. In other words, it is like many other grasses in its inherent adaptability, although it does particularly well in sandy soil, using it roots to anchor the particles together. 

I'd also like to suggest that it would make a great ornamental, at least in its dried state, and in the dusk ;-)

Tuesday, October 13, 2020

White flowerheads in a white landscape: Chloris virgata in White Sands National Monument


In Fall of 2019 I visited the White Sands National Monument in New Mexico to view some of the tenacious grasses that thrived in this relatively inhospitable environment.

While dropping by the visitor center of that park I was met by a wonderful sight. All by its lonesome on one of the pebble strewn islands that marked the boundary of the center was a single plant. It stood straight and tall, the white flowerheads above it gently waving in the breeze. 

It was not an ornamental, planted by some gardener, but a wayward seed that had sprouted and grown into a mature plant, struggling past the pebbles and flourishing in the light.  

I found the pictures of this grass again recently, and managed to tentatively identify it as Chloris virgata, a widespread species that nevertheless was not present in New Jersey. It has many common names, such as feather fingergrass and feather windmillgrass.

It is an annual grass that is worldwide in distribution and because of its hardy nature can oftentimes be found in disturbed areas as well, such as roadsides.

I must admit, I knew none of this information when I first spotted it that fine day in New Mexico. All I knew was how amazing it was to find such a beautiful plant growing tall and firm and proud in that isolated visitor center.

Sunday, October 11, 2020

My houseplant is a grass!

Some people decorate their homes with orchids, and many go with the old standbys, tough aroids like Philodendrons. 

Winter is coming, and now I have a new houseplant.

It started as one culm, a single leaf blade coming out of the ground. But fairly soon the tiny pot that it called home was filled with red-green leaves.

Meet my new houseplant. Japanese Blood Grass. Cogon Grass. Imperata cylindrica.

How weird is that? ;-)

Saturday, October 3, 2020

Meet the strange shimmering spikelets of Schizachyrium scoparium (Little Bluestem)

When an observer looks at the seedheads of Schizachyrium scoparium (Little Bluestem), they may gasp at its beauty, and marvel at the whitish fluff that decorate the reddish main axis of the inflorescence. But little do they know what a complex piece of biological engineering that whitish fluff is when viewed at the macro level. 

As many of the Orang Poa (Grass People) know, the unit of reproduction in grasses is the spikelet. The spikelet contains the florets ("flowers") of the grass, and of course the florets (like any flower) contain the stamens (male) and pistils (female). 

In the case of S. scoparium, the spikelets form a complex little unit with many parts. 

Pairs of spikelets run along the axis of the raceme of the inflorescence. Each pair is composed of 2 spikelets (see image below).

The smaller spikelet in the pair sits on top of a pedicel, and is rudimentary and hairy. The larger and fertile spikelet is sessile, with two structures called glumes completely covering the two florets inside. One of the florets is sterile, while the fertile floret has a long bent awn that extends from its central nerve and extends out of the glumes.  You can see the bent awn of the fertile floret in the image below, but the rest of the floret is hidden inside the enclosing glumes.

The unit of dispersal is composed of the two spikelets, in addition to a short segment of the raceme axis. An abscission layer below the axis segment allows the seed-carrying unit to disarticulate from the raceme, and the hairs on the rudimentary spikelet and the axis segment allow it to be carried by the wind for very short distances (typically less than 2 meters from the mother plant).

As I watched, one of the "seeds" floated onto the ground and I took pics of it before the wind could blow it away (see image above). 

(B) is the bent awn of the fertile floret that is being hidden between the enclosing glumes, and (A) is the rudimentary spikelet which sits on a pedicel. The axis segment that connected the unit to the next spikelet pair is labeled (C), and you can see at the top where it was detached from the raceme.

So the next time you see seedheads of S. scoparium, just remember how such simple looking structures actually are composed of wonderfully intricate parts! 


Thursday, October 1, 2020

Is Distichlis spicata (Saltgrass) precocious at Cheesequake State Park?

Distichlis spicata (Saltgrass)

During my last trip to Cheesequake State Park, I noticed that in the area closest to the entrance of the walkway to the Crabbing Bridge, there were quite a lot of dried up small seedheads poking out from the grass.

Not knowing what they were I used my macro to take a few photos of the seedheads (amazingly enough, the macro could focus on faraway and smaller items).

Distichlis spicata (Saltgrass)

When I got home, I was delighted to find out that the grass was another of the common species inhabiting salt marshes. Distichlis spicata is a small-sized perennial that is extremely salt tolerant, and can expand via both stolons and rhizomes. It tends to be found in the high marsh, and the interesting thing about the species is that it is dioecious, with male and female flowers residing on separate plants.

Although such an arrangement is common in animals, in sessile plants this might mean that population growth in the species is slower because the plants cannot self-pollinate. There is also 50% less pollen in the population, and the direction of travel of pollen makes a difference. If pollen goes from one male plant to another male, then it is wasted, although this can be somewhat negated by using vectors such as insect pollinators that can be pushed in one direction.

Distichlis spicata (Saltgrass)

Nevertheless, many species of plants are dioecious, so the mechanisms by which they compete against monoecious plants have been investigated.

Some studies have suggested that long lived perennials achieve this by the dioecious female producing many more seeds than their competitors. Another possible mechanism is to flower earlier during the lifecycle, so that the population size grows incrementally faster, and some papers have seen this happen as well.

As a wind-pollinated grass with no insect pollinators, one has to wonder whether D. spicata uses one mechanism or the other (or maybe both), but some studies show this species has low seed production. So the question is whether D. spicata flowers earlier in its development, or whether its ability to spread and dominate an area comes through some third option. Perhaps vegetative reproduction through rhizomes is the secret weapon that it uses to overcome the dioecious dilemma.

There's so much we don't know about our fellow inhabitants on Earth!