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). https://doi.org/10.1038/ncomms14245

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. 

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.

Reference

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.

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

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?

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 ;-)

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.

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? ;-)

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! 

 

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

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).

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.

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! 

Flowering at the Crabbing Bridge: Sporobolus alterniflorus at Cheesequake State Park

I've already done several posts on Cheesequake State Park, and how it is notable because it lies in the transition zone between two different ecosystems, and harbors organisms that are native to both south and north New Jersey. It is also interesting to me because it encompasses a salt marsh, and is the home to several grass species, each of which is specific to a particular portion of the salt marsh.

Phragmites australis looking out over Hooks Creek Lake

The place is also a great hiking location, with well-marked trails that are wide and clean. Although there is no high viewpoint in the trails that we've done,  there are various stops at the edges of lakes and ponds. The facility also has a sandy beach that fronts Hooks Creek Lake, and various lookouts that survey nearby marshlands.

(PA) Phragmites australis, (SA) Sporobolus alterniflorus, (SP) Sporobolus pumilus near the Crabbing Bridge

We went there again today to hike, and I spent some time in the Perrine Road Trail, in the general vicinity of the Crabbing Bridge. This where one can see all 3 major grass species in the area (see image above). The invasive Phragmites australis (PA) occupies areas close to the  eastern end of the extended "walkway", with Sporobolus pumilus (SP) next to it, while the low marsh species Sporobolus alterniflorus (SA) is situated close to the water itself.

S. pumilus in front of P.australis stand

It's fairly easy to distinguish the three, with P. australis being much taller than the other two, the darkish flowerhead rising high up in the air and usually drooping to one side. S. pumilus beside it is much shorter, the long thin leaves close to the ground to form graceful clumps.

View of S. alterniflorus from walkway to Crabbing Bridge 

S. alterniflorus is intermediate in size, and occupies most of the area all the way to the actual Crabbing Bridge. When we were walking over the walkway, I noticed that many of the culms had flowerheads in bloom.

The inflorescence was a spike, quite pointed at the end, and mostly green in color. 

White anthers decorated the spikes and dangled out from the flattened spikelets. The anthers seemed quite long, almost sausage-like in shape. The term grub-like might even be used to describe it.

I spent some time taking pics of various blooms, which was not an easy task given that the walkway was perhaps only 2-3 meters in width, and due to Covid-19 restrictions I was trying to remain a bit far away from other passing visitors.

When people passed I tried to keep as close to the edge as possible, and the thought that I might overbalance and fall into the grasses was a constant thought in my mind. I can only imagine the commotion that would ensue if that happened.

Oh, the things we have to do for our passions ;-)

Spikelets of Muhlenbergia reverchonii "Undaunted"

I bought a Muhlenbergia (along with a Miscanthus sinensis 'Morning Light') cultivar at the end of 2019.

Both were dried and seemingly dead, and therefore discounted by the store, but I figured that they would sprout again in Spring. So I kept both in our garage, making sure not to wet the soil, and as expected this Spring both grasses came to life.

Unfortunately, neither seemed especially vigorous at the beginning, although as Fall came both have continued to grow larger. The Miscanthus hasn't flowered, but the Muhlenbergia did send out a somewhat thin spray of pink blooms.

 

The spikelets were quite tiny, but I did manage to take macro shots of some, which clearly showed the short glumes and awned lemma of the single florets in each spikelet.

I had planted the Muhlenbergia close to a stand of Japanese Blood Grass (Imperata cylindrica), and over the course of the year the JBG had started to envelope it, and perhaps this had also affected its size. I'm therefore going to transplant the grass away from the JBG next year and hope the specimen performs better.

Who says I'm not ornamental? Native Schizachyrium scoparium (Little Bluestem)

A lot of times our native grasses get the short shrift even from gardeners, who tend to want the pricey ornamental grass cultivars sold by stores.

But I found this Schizachyrium scoparium on a roadside filled with Little Bluestem, and look at it now. The late afternoon sun was shining on it, and I noticed it looked quite red from a side angle, so I took a quick pic using a cellphone (the one with the Leica lens though).

What a beautiful gem, and 100% native and wild type!

A Lovecraftian Field of Cogon

Image: Courtesy of Ashley Snodgress 

In the tropics there are whole mountain ranges covered in cogon, the waving blades of grass standing triumphant in a land denuded of other competing plant life. They call these mega-grasslands sheet Imperata, and these are only the most visible signs of a species that dominate up to 4% of the total land mass of tropical Asia. In some places like Sri Lanka, cogongrass covers an astounding 23% of the country! Even more amazing, this species has been estimated to infest up to 500 million hectares worldwide,  which is nearly the size of the total land area of the continental USA.

In the USA itself, Imperata cylindrica is limited to the subtropical southeastern parts of the country, where it lays waste to about half a million hectares. Although the vast cogon grasslands that is so prevalent in tropical Asia are mostly absent in America, I am sometimes astounded by how rapidly the species can spread to cover a large area even in relatively developed land. 

In the image above, which was taken in Florida, the landscape seems almost alien and surreal. The entire area is covered in cogongrass, with only a few trees and other taller shrubs scattered about like discarded flotsam in a vast green sea. It almost makes one wonder what lovecraftian monsters might lurk and slither within its dark depths.

Little Bluestem's Mountain Loving (Schizachyrium scoparium)

Note: My 55 mm lens is screwy, so you'll pardon me because the pics here were all taken with a cellphone camera, though it does have a Leica lens.

I have an inordinate fondness for Schizachyrium scoparium (Little Bluestem). I think it's a combination of its smaller size, its very distinctive habit, and its really cool reddish coloring when Fall comes along. Plus, the species is a member of the "Four Horsemen" of the Tall Grass Prairies, and you can't get any more native than that.

I also hike a lot, and when I get near the top of moderately tall mountain summits, I sometimes spot colonies of this species rising from the stony outcrops like crimson sentinels. It always gives me a thrill to see them, no matter how many times this happens. It's like seeing an old friend again, one who has endeared itself to your heart.

I encountered Little Bluestem again when I drove (then hiked) up Prospect Mountain, near Lake George in New York State. Colonies of this species were scattered on the summit of the mountain, as well as along the roadway that led up to the summit.

S. scoparium seems to thrive when there is lots of sunlight and bare rocky ground, and both are plentiful up where the air is fresh and the wind is sometimes cold. In this case, about 620 meters above sea level, well below the tree line, but sunny enough to make it very happy.

Up here the grass rose from the surrounding stone, their straight reddish forms quite arresting. One particularly large (and flowery) individual stood next to a boulder, the sinuous curves of part of Lake George glittering behind it.

I still remember seeing this species in June 2019 while hiking the Summit Trail in Jenny Jump Forest in NJ. I did not know the name of the grass then (how things have changed in such a short time!), but I still marveled at the sight of the reddish hued straight grass at the summit of Jenny Jump.

So the next time you hike up one of the mountains in the eastern part of the USA, keep a look out for one of these native beauties!

A mossy life in the clouds

The Cascade Mountain Trail near Lake Placid in New York State is a moderate hike that takes you above the treeline to bald rocky outcrops 1250 meters above sea level. At this height, alpine vegetation can be seen among the plant life, their low slung bodies hugging the ground in order to shelter from any strong winds.

I was eating lunch next to large boulders, when I noticed some vegetation hidden in the shadow of the rocks. When I looked more closely, I was delighted to find some grasses growing from a luxuriant carpet of moss.

The grasses had very fine leaves, and dried seedheads rose from the clumps like tiny white flags. A quick investigation showed the panicles contained the remnants of extremely tiny spikelets.

I took macro shots of the spikelets, which were probably only 1-2 mm in size, and based on that and the leaves tentatively identified the species as Deschampsia flexuosa.

The association of this species with mosses immediately brought to mind the habits of its sister, the noteworthy Deschampsia antartica, which is only one of two vascular plants that have managed to colonize deep into Antartica.   That species is also frequently seen growing from mosses, and researchers have found that specimens in such an association are larger and healthier than those individuals living on bare rocks (Casanova-Katny and Cavieres, 2012).

They surmised that mosses help the grass by modifying the surrounding environment, perhaps by increasing soil moisture and soil nutrients content, or by also buffering temperature compared to bare areas.

Whatever the reason for their association, my surprise find at the summit of Cascade Mountain certainly added to the enjoyment of the hike!

Literature Cited

Casanova-Katny M. A., Cavieres L. A. (2012). Antarctic moss carpets facilitate growth of Deschampsia antarctica but not its survival. Pol. Biol. 35 1869–1878