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Author Archives: George Rogers

About George Rogers

Professor of horticulture and botany at Palm Beach State College

Colombian Waxweed is a Seed Trebouchet (maybe)

Colombian Waxweed is a Seed Trebouchet (maybe)

This article has a lot analogies.

Cuphea carthagenensis

(Cuphea comes from Greek for curved, noting the bent flower base. Cartagena, Colombia, is the site of the original specimen.)

Lythraceae, the Crape Myrtle Family

A running theme in my botanical life is, hey, no need for exotic locales to see the best of botany, the back yard ain’t bad.   The plants we tromp while looking for something fancy are often overlooked treats, like shy classmates.  Nobody told Mother Nature to put all the good evolution in tourist brochure locales.   As an example, in wet disturbed areas across much of the Southeastern U.S. and far southward is a pretty little plant you might call a wildflower, or a weed, or “Colombian Waxweed.” Books will state it is not native to Florida, but I never trust such designations with widespread self-fertile masters of dispersal having unknown histories.  When and how it got to Florida from tropical American latitudes is anybody’s guess.

Cuphea carthagenensis 4

Colombian Waxweed by John Bradford.

Gardeners know the genus Cuphea from such beauties as bat-faced cuphea, candy-corn, cigarplant, and Mexican-heather.   They are pretty, including Cuphea carthagenensis in a modest sort of way.

The long sticky hairs on Cupheas are so graspy-claspy they could remind an observer of the tentacles on carnivorous sundew.  Here is an excerpt from Popular Science Monthly 1904:

cuphea pop sci monthly

Look closely at the photo below of a partial flower touched by a steel needle.  The hairs grabbed and hugged the shaft, conforming instantly to its shape.   Those are some serious “tentacles,” marauding ants beware!

cuphea clinging

Cuphea flower tube with clasping hairs hugging needle shaft. They grabbed the needle instantly upon touching it.

A second point of human-Cuphea contact is the oil from its seeds garnering attention relative to human dietary health, possibly as oil crops.   The main function of seed oils is as compact high-energy nutrition for the embryo.   In a wetland weed, the oils might additionally resist water damage.

Cuphea carthagenensis has one of the weirdest seed dispersal systems I’ve ever seen.  The “placenta” is the structure inside a fruit where the seeds are attached.    Repeat, inside the fruit.

In today’s species the world’s wackiest placenta thickens, lengthens, and bends upwards ripping open the horizontal flower, busting through the top off the fruit and opening the overlying flower tube.     Think of Dracula sitting up in his coffin, tearing through his shroud (the fruit) and popping the top off the coffin (the horizontal flower tube).

cuphea opening

Cuphea seed presentationcropped

The open flower tube is pointing toward us at the bottom of the photo.   The big pinkish placenta has risen, opening the top of the flower tube.  Six seeds are visible on the placenta.

This leaves a very odd “fruit” looking like a bent shovel, the shovel handle (Dracula) being the placenta, and the toothed shovel blade being the remains of the torn flower tube. Upon rising, the enlarged placenta has seeds on it, dispersing to leave the placenta bare.  The shovel blade is held. nearly horizontal.  The placenta leans back. The unit is hinged to the main stem by a short stalk attached near the angle where the blade meets the handle

cupheaseedless

Open flower tube (shovel blade) to the left.  Placenta (shovel handle) pink on the right.   Seeds removed.  The hinge is behind the blade-handle junction.

The exposed placenta passes through a pinkish phase.  Why?  Could the color attract creatures involved in dispersing the seeds?   Birds?  Possible, but the shovel units are tiny, and birds just don’t ring likely.  Insects?   Possible, but there is no apparent reward, I’ve never seen any,  the  seeds are not particularly sticky, and the big seeds would be a massive burden on a bee, although an insect visitor coud shake them loose if not cart them off   Again, doesn’t strike me as likely.   Rather, I suspect the colorful placentas enhance the overall attractive display of the entire plant, helping to draw distant pollinators, who once nearby divert to the actual flowers.    Room here for speculation and research!

More abundant than bees, more reliable, and vastly more powerful is the driving rain.   A  raindrop has punch, and the open flower tube shovel blade is sized and positioned for raindrop bombing.

cuphea splash

A raindrop smacks the blade downward, popping the hinged placenta up to catapault the seeds.  It makes sense for a plant inhabiting rain-puddle habitats to launch seeds during the deluge.  The seeds go when and where the rainwater goes.

Why is the blade toothed?  Maybe to help capture raindrop impact, yet to also allow drainage.

Cuphea Trebuchet_Castelnaud

 
2 Comments

Posted by on May 17, 2019 in Cuphea, Uncategorized

 

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 Are Lichens Tree Parasites?

Never say never.

The dogmatic answer to that frequently posed question is a comforting “no” echoed throughout garden publications.  Here is a typical statement from the New Mexico State University Horticultural Guide H-167:

“Lichens may rest directly on the bark or be attached shallowly to it, but they do not enter the inner bark where food is transported, and hence do not rob the tree of nourishment. They are not parasites.”

IMG_7376

Lichen with the emerging side-branch kaput.

A trouble with dogmas is that while they spread and simplify,  gaining emphasis, occasionally somebody goes back and checks them out.   Not that finding parasitism in lichens is new. One of the links below dates from the 80s.    And, because lichens are not a single “thing,” but rather many unrelated species in diverse symbiotic relationships,  ixnay on big sweeping generalizations.

I’m not posting this to shock treehuggers.   Seems that under most circumstances most lichens are mostly okay. There’s no existential threat, arboreal apocalypse, or actionable garden info here.    Just interest…

Assuming that lichens are never parasitic is actually too good to be true.    To cite recent experience, would you leave the dog alone with an Italian sub?  A fox with the henhouse?  Me unsupervised in a Dunkin Donuts?   Lichens are fungi bundled with algae or cyanobacteria.   Fungi are tissue-invading machines.  That is what they are good at.   Their threadlike hyphae penetrate and digest organic matter.  So why should a lichen fungus always “behave” and never help itself to a bit of the host tree’s substance?  A little side-steppin’ shoud be expected.

What’s remarkable is that lichen fungi are not more parasitic to their hosts, although the hosts have defensive mechanisms, most conspicuously shedding bark and pesky pests thereon.   Lichen fungi do invade tree tissues, probably mostly on young twigs.   Researchers have long been aware that the lichen “oak moss” Evernia prunastri  and species of similar Ramalina penetrate the bark, including the living sugar-conducting layers, and sometimes into the wood beneath. “Lichens are not parasites,” my ass.

Pause a moment.  It may help to clarify that bark (phloem) is dead to the outside but alive and transporting sugar in its inner layers.   Immediately interior to that is the water-conducting wood (xylem). Together the phloem and xylem are the circulatory system of the branch.

Botanists who have looked into lichen parasitism have found that host branches can lose their leaves outward to the leaf tip from the point where the lichen is attached.  That is, water transported out the branch after passing the lichen seems to cause leafdrop. This could be due to toxicity and/or to tissue damage.   Alternatively,   and not an idea original with me, it could be adaptive for the lichen to defoliate the branch for increased light exposure.  Weirder things are known.

It is not just oaks.   Locally on Bald or Pond Cypress small tufted lichens* sometimes perch on young branchlets, which may become leafless or lifeless out past the lichens.  In the photo below the Cypress branch is healthy below  (to the right of) the largest lichen, sprouting side branches.   The side branches at the point of lichen attachment, however, are dead, and those farther toward the branch tip (left of the lichen) are stunted or missing.

Ramalina damage on Taxodium 1

All good until you get to the large lichen.  At the lichen attachment and beyond (to the left) , side branches dwindle.    For that matter, the smaller lichens seem to have killed and shortened side branches at their attachment points too.

To see if the lichen affects the living inner bark and/or into the wood, I sliced branches lengthwise at the point of lichen attachment.  Bark at the lichen attachment point is thickened and different from bark elsewhere.

Taxodium with Ramalina

At the center, bark (brown layer) thickened under lichen (gray) attachment.  Normal bark appears at far right.

Looking more deeply, the wood interior to the thickened bark is discolored as in the photo below:

Ramalina wood damge

Discolored wood under lichen attachment point.   Bark is brown layer on the right.

To sum it up, these lichens are entering the living inner bark and penetrating (or at least damaging) the underlying wood, killing or stunting side-branches, and ultimately killing the host branch tip distal to the lichen.   But fret not, the suffering twigs are few,  and maturity brings toughness ….so the outcome seems merely a tiny bit of free pruning.

Ramalina wood discoloration 2

Wood discoloration under lichen attachment.

=================================================================

Dig in deeper:

Click for an older paper on this topic.

Click for some recent views from the West Coast, and sources.

The identity of the photographed lichen is not relevant to today’s article.  I’m no lichen expert and  have no interest in peripheral concern with species name.   I’d be glad to share my tentative identification privately by e-mail upon appropriate inquiry.

 

Ground Hog Day In the Periphyton

John and I worked today in the Haney Creek Trail natural area near Jensen Beach, Florida, although the scope of the discussion extends to multiple local wild places.  An intriguing habitat type has no particular name:   Let’s call them freshwater mudflats.

mud flat

Pond with aquatic species (green), in a ring of seasonal freshwater mudflats.  During the wet months the entire area is inundated.

In these places seasonal inundation alternates with the pond bottom mud exposed bare naked anew each dry season.  Sort of like Bill Murray’s Groundhog Day…ecological succession set back to “go” in an endless loop.

I don’t know to what extent various mudflats around here are the result of human activity.  Either way, they are an exotic universe to explore

On the flat I’m using to base today’s account approximately six species dominate, accompanied by several subordinate interlopers. Different mudflats or even different portions of the same flat have different species mixes.   The list below excludes the truly aquatic species persisting where the water has not receded.   We’re talking about “land plants” on drying mud.

Here’s the dominant species list…

  1. Dog Fennel (Eupatorium capillifolium) in the Aster Family. This smelly weed invades just about any disturbed site where the sun shines, from cow pastures to today’s habitat, where it seizes upon the extreme disturbance of wet bare mud. Ideal!   The seedlings are probably the most abundant babies on the site.
IMG_7004

Dog fennel seedling in the periphyton mat.

2. Sweetscent (Pluchea odorata), likewise smelly, is in the Aster Family. Its pollinators are diverse, yet  in my experience mostly abundant enthusiastic wasps.  The tiny individual flowers are clustered, with each cluster swaddled in small purple leaves (phyllaries) giving each  cluster the look of a single urn-shaped flower, resembling flowers in the Blueberry Family.  Wasps poke their faces into the opening of the urn.

Pluchea with wasp 2

Here is a brief clip of a wasp “working” the urn-shaped flower clusters…

CLICK (action slowed a little)

  1. Mock Bishopweed, aka Herbwilliam (Ptilimnium capillaceum) in the Carrot Family has its delicate white flowers in umbels reminiscent to northeners of Queen Anne’s Lace.

IMG_7089

ptilimium flowers close1

Mock bishopweed flowers – they can self-pollinate

4. Lax Hornpod (Mitreola petiolata) in the Logania Family was the topic of last week’s blog.

5. Bighead Rush (Juncus megacephalus) in the Rush Family loves mud. Its spherical seedheads host a moth larva whose identity I’m not sure.

juncus megacephalus with moth larval cases

Bighead rush. The white items at 4 and 6 o’clock are moth pupal cases.

6. Fragrant beaksedge (Rhynchospora odorata) in the Sedge Family is scattered throughout.

A mix of unrelated plants, and surprisingly small species count.  The surrounding woody-swampy areas house probably 100 different species, so how does a seasonal mudflat filter the community to a dominant half-dozen plus  a handful of others?

Let’s look at the environmental difficulties.

Difficulty 1.  SEASONAL WATER EXTREMES.  The plants have to cope with flooding half the year, then saturated soggy soil, then sun-baked drying mixed with intermittent deluges.  How many species can transition from flood to desert?   Few of today’s species actually live in standing water.   Rather, they recolonize the mud each year by arriving anew via wind-borne seeds and/or persisting in the mud seedbank.

Dog Fennel and Sweetscent seeds (achenes) fly on parachutes.   Although they may also survive in the soil seedbank, their seedlings seem scattered relatively randomly on the mud as opposed to showing a strong relationship to the receding waters. I vote for “new rearrival annual” as  important for the parachute species.

All the others, by contrast, have small, hard, durable seeds or achenes easily dispersed by water but not by air, and  presumably surviving in the pond bottom mud from year to year.   Published research documents this ability for Mock Bishopweed’s seedlike fruits, which float.

ptilimnium fruit close

Mock bishopweed fruit floats, and can remain viable for at least several months.

This species seems to prefer germination in the natural “mulch” formed by dead aquatic species…out with the old, in with the new.   Its tiny seedlings flower as toddlers, making sure of reproduction before the next flood.  The flowers can self-pollinate, further assuring seed production before Noah time.

ptilimnium baby with dragonfly

Baby mock bishopweed, already with flowers.  Mulched among dead aquatic sedges killed by dropping water level.

Lax Hornpod has the most conspicuous relationship to receding waters.  On the wet mud within a foot or two of the water line its seedlings rise in abundance.    With increasing distance from the falling water the older Hornpods diminish in abundance and increase in size.   The pattern suggests that the seeds wait in the mud ready to sprout the moment the water recedes.   It too is self-pollinated.

mitreola babies

Hornpod babies pop up like mushrooms the moment the mud surfaces.   These are a foot back from the water’s edge.

Difficulty 2. BAKING IN THE SUN  Brutal sun exposure goes with the territory.   Except for Sweetscent and Hornpod, all six species have narrow leaves or finely divided leaf segments adapted to minimizing sun exposure while maximizing wind-cooling.    The filamentous leaves of Mock Bishopweed and Dog Fennel are almost identical:

IMG_7233.JPG

Dog fennel on left. Mock bishopweed on right.

Sweetscent has  protective hairs and secretions.    Hornpod has the most-“normal” leaf blades and may be the first to succumb to drying and heat.

Difficulty 3.  HORRIBLE SOIL The plants live on sand mixed with fossil seashells.  Submersion half the year interferes with “normal” soil microbes, with nutrient cycling, and with symbiotic mycorrhizae.   Nutrients wash away during inundation.  Wet soils generally have only a thin organic layer.    Oxygen would be scarce much of the year.   At some points the sandy soil is suffocating wet, and at other times bone dry.

Flooding, suffocation,  radiation…No wonder only elite species cope!

The mud-dwellers have one apparent advantage…periphyton. Periphyton is the mat of algae, cyanobacteria, fungi, rotting detritus, sticky goo, and associated microfauna that floats in the shallow waters during the wet season and settles as a crust on the mud as the waters recede.

IMG_6999

Stranded dry periphyton mat.

How does the mat impact the dry-season plants living on it?   This is poorly studied, although a 2018 investigation by biologist Lu Haiying and collaborators considered this with respect to paddies.  Among their observations, the periphyton crust:

  • Is involved in nutrient cycling between the water and soil, retaining and releasing nutrients, sort of a green liver
  • Improves the soil structure
  • Serves as a slow-release bio-fertilizer

The periphyton may help overcome dormancy in seeds of some species.   Just a guess, but an experiment to try, especially with Lax Hornpod.  Periphyton probably blocks soil drying, and retains rainwater.  Further, it dampens out temperature fluctuations.

All the nutrients captured, modified, or created by the algae and cyanobacteria during the wet months eventually become available slow release to the mud-dwellers.

Periphyton is loaded with Cyanobacteria, and many of these are nitrogen-fixers.  The brief clip below shows the Cyanobacterium Oscillatoria wiggling in the stranded periphyton crust after rewetting (action speeded up a bit).

CLICK to see the dry periphyton resurrect.

peri wakes up

This graph shows carbon dioxide production (respiration) by a few chunks of “dead” dry periphyton crust.  They were waterd at the start of the graph.  The chunks sat flatlining for about 180 seconds, then life!  The periphyton wakes up and “starts breathing” within 3 minutes of moistening.

 
4 Comments

Posted by on May 3, 2019 in Periphyton, Uncategorized

 

Lax Hornpod Needs Neither Bird nor Bee!

Mitreola petiolata

(Mitreola means little mitre, because the fruit looks like a Bishop’s mitre.  Petiolata indicates the leaves have stalks.)

Loganiaceae

Mitreola petiolata is a worldwide warm-climate weedy species whose point of origin and history of dispersal is unknown.  Its intercontinental range include all of Florida.  Let’s call it a native species.

mitreola petiolata plant - Copy - Copy - Copy

That huge pantropical distribution stands out in the small genus Mitreola where most of the other species have narrow ranges scattered in Africa. Asia, Australia, Borneo,  and Madagascar.   Mitreola sessilifolia, similar to today’s species ranges across Florida and much of the southern U.S., extending into Mexico.

mitreola map

Each yellow circle represents one Mitreola species.  Mitreola petiolata is “everywhere,” the purple lines showing its global reach.

Mitreola petiolata has pretty little white flowers with a curious donut of hairs partly blocking the flower’s throat.

Mitreola fresh flower

Highly magnified. The flower is about 1.5 mm in diameter.

And speaking of curiosities, the pod is a two-horned “Bishop’s mitre.”

mitre

mitreola fruit - Copy

Pod

Weedy species such as this distributed far and wide often reproduce free of the need for a male plant and a separate female mate to establish together for cross pollination at each step during world conquest.  Botanical imperialism is more efficient if you spawn alone.  There are different ways to accomplish that.   Mitreola petiolata uses extreme self-pollination within individual flowers.

mitreola inflorescence

Back in 1841 botanists John Torrey and Asa Gray noted, “the pollen tubes are often so copious, even in dried specimens,  as to fasten the anthers to the stigma.”  This observation is 178 years old, and I’ve never seen anyone record checking it out since.   It is about time! This is going to be better than Geraldo Rivera opening Al Capone’s vault!  Get ready!

Be patient one moment though, after almost two centuries the mystery will hold 30 more seconds while a little background refresher may help explain what those two were talking about.   In a “normal” textbook species, a bird or bee transfers some dustlike pollen grains from the pollen-producing anther of one flower to the pollen-receptive stigma of another flower.   Then a tiny thread called the pollen tube grows like a root from the newly landed pollen grain down through the stigma and style to the ovary, carrying sperm to fertilize the baby seeds there.  To repeat, the pollen tube is a tiny sperm-bearing filament extending from the pollen grain to the baby seed within the newly pollinated flower.   Here is a helpful diagram:

pollen tube diagram2

Textbook normal pollination. Pollen grain (yellow) deposited onto stigma (blue) by pollinator.  Then pollen tube (yellow) snakes down to deliver sperm to seed (violet).

Okay then, we now can carry forward knowingly. Mitreola petiolata has a ring of five pollen-making anthers attached inside the flower. The anthers unite to form a cap covering the  stigma   The pollen grains inside those anthers do something weird, they all sprout pollen tubes while still inside the anthers that made them.  Today’s species skips the messy business of birds, bees, and pollen transfer to a different flower.

mitreola flower diagram - Copy - Copy - Copy

Top image:  diagram of the Mitreola petiolata flower.  Middle image: anthers (yellow) united into cap over stigma.   Bottom:  anther cap has been pulled away from stigma revealing  pollen grains and their pollen tubes penetrating into the stigma.

The countless premature pollen tubes form a network lacing the anthers to each other and to the stigma in a wild orgy of self-pollination.   When this has occurred, as Torrey and Gray noticed back the year President William Henry Harrison died in office, the mob of pollen tubes have stitched the anther cap firmly to the stigma.

MitreolapetiolataApril25AnthersStuckToStigma - Copy

This is the base of the flower with the petals removed.  The anther cap (gray above the center)  is tied to the stigma hidden beneath it.  The 3 white flaps are anther attachment points left behind when the petals were torn away…remnants of the petals and their connections to the anthers. This photo shows the same info as the middle image in the diagram above.

When the anther cap is yanked away from the stigma under a microscope, the stigma remains covered with pollen tubes burrowing in for sperm-delivery.

MitreolapetiolataApril24style - Copy

This is the stigma with the anther cap pulled off.  The tangle on the left is a mass of pollen grains and pollen tubes left behind from the anthers, and penetrating the stigma.  Extreme self-pollination! The style is the shaft in the middle, and the large body on the right is the ovary.  This photo matches the bottom image in the diagram above.

I’ll bet every flower on every Lax Hornpod in every wet meadow around the Globe matures a fruit filled with self-fertilized seeds.  It’s an inside job!

 
6 Comments

Posted by on April 26, 2019 in Mitreola petiolata, Uncategorized

 

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Blue-Eyed Grass

Sisyrinchium angustifolium

(Sisyrinchium comes from Greek for “pig-snout,” reportedly because hogs dig the roots, although to my eye the yellow anther cluster resembles a pig snoot.  Angustifolium means narrow-leaved.)

Iridaceae – the Iris Family

Sisyrinchium angustifolium 1

Sisyrinchium angustiphyllum by John Bradford

Thanks to rain, no fieldtrip this morning, so I’m turning back the hands of time to the wet meadow my PBSC botany class explored yesterday at Sweetbay Natural Area near Palm Beach Gardens, Florida.  The wet prairie flowers are glorious now, and the fairest of the fair is Blue-Eyed Grass.

Sisyrinchium xerophyllum 2

S. xerophyllum by JB

Sisyrinchium is a genus with about 80 species, essentially native to the Americas.   With controversial species definitions, we have 3 or 4 species locally, ranging in preferences from sun-cooked scrub sands to soggy meadows.  We’ll concentrate on narrow-leaved blue-eyed grass, Sisyrinchium angustifolium so elegantly in flower now.   Beautiful!   Looks like a tiny Iris to which it is related.   The similar S. nashii has tufts of fibers at the base of the clump.

sisyrinchium

Sisyrinchium angustifolium ranges all the way from Palm Beach palms to Canadian ice.  Those blue flowers with fancy yellow eyes host mostly bees and certain flies,  not to exclude possible butterflies.    That tidy picture belies a complex floral structure and equally complex evolutionary history.

_DSC9948Toxomerus geminatus-Sisyrinchium angustifolia Duette Lampkin

Toxomerus geminatus Syrphid Fly enjoys Sisyrinchium. Photo contributed by John Lampkin.

The flower has an idiosyncratic construction probably dating back to bird-pollinated ancestry according to the late botanist Verne Grant, famous for interpreting floral features functionally.  The seed-bearing inferior ovary hangs below the flower out of harm’s way relative to big abusive pollinators such as birds.    Even more indicative of avian predecessors, the center of the flower sports a column made of the male stamens fused into a tube around the female style and stigmas.   Dr. Grant interprets such a stamen tube as a bird-beak-shield, as you see in big Hibiscus flowers.   The tube protects the delicate style in the fashion plastic insulation protects a copper wire.

Sisyrinchium stigmas hidden

Stamen tube, the column, at center of flower. Style and stigmas are hidden within.

Sisyrinchium stigmas protruding

Later…stigmas protruding from column tip.

Sisyrinchium stigma bent

Later still, stigma bent outward between anthers.

 

At the base of the column is a brush of large yellow hairs, and at the column tip are the bright yellow anthers.  Both features beg attention.   First the hairs.   Their role in attracting pollinators to today’s species is unclear, possibly due to its northern distribution.  In Tropical American Sisyrinchiums  the hairy brush secretes oils to feed tropical bees.   But North America is not a land of oil-collecting bees, and it seems our species has lost the oil.  Despite possessing the hairs normally associated with oil production, tests have shown S. angustifolium surprisingly bereft of oil.  But who knows, maybe the beard still contributes somehow to pollinator satisfaction.    The scentless flowers are another point consistent with bird-pollinated ancestry.

sisyrinchium hairs

Hairs at column base. Where’s the oil?

To wrap it up, how about those three big yellow pollen-producing anthers topping the column?   When the flower is young they are shedding yellow pollen but no female parts stand encased within the column.   The tip of that hidden style has three slender stigmas (pollen-receiving lobes).   The stigmas eventually push up into the light of day above the anthers, switching the flower’s sex from male to female.  The stigmas bend finally outward between the anthers.

sisyr

 

Mangrove Roots Pushing and Maybe Pulling

Last week John and I tested Red Mangrove branchlets for sun-generated pressure and found it, the pressure presumably forcing air down to the roots submerged in deep, wet, tidal, de-oxygenated mud.    Most branches when cut off from other species show a distinct negative pressure, suction, the opposite of Red Mangrove.

Rhizophora mangle 6

Red Mangrove fruits and embryos by John Bradford.

We hoped the roots would show continuity with the forced-air-ventilation from above by being positively pressurized too.   We connected a couple cut-off Red Mangrove roots to a pressure meter.

Under bright sunshine the pressure climbs dramatically as shown below:

Red Manrove Root Pressure

Pressure increasing for 150 seconds in bright sunshine.

When the tree is shaded, we could not find pressure.  Sunshine was required.  Look at the correspondence between light intensity and pressure below:

rhizophora injured

Blue line is pressure.  Rusty line is light intensity.

While we were in a Mangrove habitat today, we thought too about Black Mangrove, which aerates its mud-buried roots with little chimneys called dead man’s fingers.   On a whim we connected the hose and meter to the top of a dead man’s finger, where air goes in.   We wondered if the air entry is passive (with no pressure change) or, by contrast, if it is “sucked” in somehow.

In the graph below see a sharp and brief yet sustained pressure drop upon connecting the meter to a dead man’s finger.  At first superficial blush it looks like maybe air is pulled in.   It would take a lot more tests to make a case for anything, and explaining it in terms of how a plant is built is going to be a challenge, although conceivable.   As explained above, cut-off branches usually generation suction, perhaps in the case extending all the way into the roots.   Guess we’ll have to explore that a little more.

Black Mangrove Root Pressure

Black Mangrove. Apparent suction at top of dead-man’s finger root “chimney.”

 

 
2 Comments

Posted by on April 12, 2019 in Uncategorized

 

Azolla Fern and Barnyard Grass Oh So Belong Together

Barnyard Grass and Azolla Fern a Match Made in Heaven

(or in a tropical rice paddy)

 

Question 1.  Guess what local invasive exotic grass is the main weed in rice.

Answer: Barnyard Grass, Echinochloa crus-galli, the English name reflecting its affinity for nitrogen-enriched soil.

Echino flowers

Barnyard Grass

Question 2. Guess what floating fern serves as a nitrogen-enriching rice paddy green manure.

Azolla Fern, Azolla filiculoides, A. pinnata

Azolla caroliniana 1

Azolla filiculoides on wet mud, by John Bradford. Highly magnified. This clump would be about 1/3 inch in diameter.

Question 3.   Guess what two rice-loving species hooked up in Riverbend Park near Jupiter, Florida.

Right!  Barnyard Grass, nitrogen-taker, and Azolla, nitrogen-maker, reunited like their good old Asian ricefield days.

EchinoAzollaclose

Barnyard Grass in the Azolla soup. (Th light green is duckweed.)

Today a spine-tingling faculty meting displaced our usual Friday botanical investigations, but yesterday was great and green —a class field trip into the botanical wonderland known as Riverbend Park, where the Native Americans and U.S. Military met bitterly in 1838.

At the edge of the cypress swamp was a reddish crescent of floating Azolla Fern.   Barnyard grass was growing like a weed in the middle of the Azolla. Like old times!

EchiniAzolla

The reddish region is almost solid Azolla filiculoides.  The  large plants, except those to the far distant right, are all Barnyard Grass.

Here is what “Bayer Crop Science” says abut Barnyard Grass vis-à-vis rice:

In rice E. crus-galli over time became the most dominant weed due to its similarity with rice that made it escape hand weeding frequently. Only the use of the selective herbicides offers reliable control. However, meanwhile several biotypes of barnyardgrass have developed resistance to various herbicides and modes of action.

And this is what the Azolla Foundation sez about Azolla and rice:

The ability of Azolla’s symbiont, Anabaena, to sequester atmospheric nitrogen has been used for thousands of years in the Far East, where Azolla is extensively grown in rice paddies to increase rice production by more than to 50%.

Although now widespread, Barnyard Grass is native to the Old World, not Florida. In Palm Beach County dwell two species of Azolla, which are the same two in China, Azolla pinnata and A. filiculoides.  Both are nice to rice.

 
1 Comment

Posted by on April 5, 2019 in Uncategorized

 
 
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