Author Archives: George Rogers

That plants position themselves relative to each other is obvious.  Every gardener has seen plants under the shade of larger plants leans out toward the light, and that seedlings germinated under the shade of taller seedlings grow extra tall and skinny in an “effort” to breach the lethal gloom.

Walk in a marsh where single species can blanket an entire area under a monoculture.  Most of the “plants” in the blanket are merely the emergent portions of single or few huge sprawling rhizomes, just as a vine covering a tree can be one big spreading sprawling individual.  In any case,  the rising stems or clumps in a marsh seem to me to space themselves into an optimal pattern,  sufficiently crowded to suppress competitors yet  open enough to allow the individual rising stems to thrive.

These Sagittaria clumps are nicely self-spaced, not random it seems.  Crowded but not “too” crowded.

Sunflower plants lean away from each other.    The inclination cuts down on competition, allowing each sunflower to grow more than if not tilted.   This mutual accommodation is strong enough to impact crop yields.

The two smaller sunflowers tilt away from their big brother, inclined left and right at the same angle.

Side view of same flowers.  The two little ones also lean forward, again at the same angle.

How does one sunflower recognize the existence and position of a neighbor?   At first blush, research shows the main mechanism to be a subtle manifestation of a pervasive fact…that plants tend to grow toward light having strong red hues, and away from light rich in far-red coloration.   Strong reds are characteristic of bright sunshine.    Far-reds are typical of shade, competing vegetation, and light reflected from other leaves.    The side of a sunflower facing a neighbor is experiencing more far-red than the other side where red is stronger.  The neighborly side with more far-red grows a little faster, bending you away from your neighbor.

In recent years there has been a growing interest in “cooperation” among genetically related plants, something already well established in the animal kingdom.  Such “kin selection” has generated a good bit of interest in the botanical world with respect to root spacings, communication via fungal interconnections, and shading.   In short, one plant may “help” another plant if it is a close relative.  No, it has nothing to do with plant “will,”  “spirit,” or  “intelligence.”

Botanist Jorge Casal and collaborators showed members of a species in the mustard family to “cooperate” in minimizing mutual shading if they are are close relatives.   Related individuals produce leaves at the same height which enhances the light reflections onto each other, and thus the competition-avoidance signal mechanism reminiscent of that in sunflowers.   Dr. Casals and associates then experimented on sunflowers finding that kinship may likewise influence their tendency to lean and give each other some space.

If you want to dig deeper:

https://www.pnas.org/content/pnas/114/30/7975.full.pdf

https://www.sciencemag.org/news/2019/01/once-considered-outlandish-idea-plants-help-their-relatives-taking-root?utm_campaign=news_daily_2019-01-03&et_rid=333916853&et_cid=2581485

Ammannia latifolia

(Johannes Ammann was an 18^th Century botanist.  Latiflolia means wide leaves.)

Lythraceae

John and I worked at Haney Creek Natural Area near Jensen Beach, Florida, this week.  Much to my delight as a lover of things in wet places, we saw an old wetland oddball plantfrind, always under-appreciated.   The sort of plant you step on looking for something “interesting.”    It is all interesting if you look closely, or if you read research by other people, especially other people with an electron microscope.   Today I’m paraphrasing an eye-opening paper by Dr. Shirley Graham (in the Journal of the Arnold Arboretum, vol. 66).  Because the work dates to 1985, I’m confident Dr. Graham and the Journal would have no objection to reappearance in a 2019 blog, and I sent her an e-mail to make certain.

Today I was doing what I like to do, walking along the dried out shore of a nearby stream-canal where only two living things were visible on the barren mud, one a green alga, the other, as at Haney Creek previously, scattered individuals of Ammannia latifolia livin’ the vida sola.  Just desolate mud, a little algae, and big red Ammannias.

What dis the Ammannia and I have in common?  We were alone on the  lifeless mud.

Life “on mars” takes a fairly special plant.  Ammannia has some obvious advantages for places that alternate between flooding and drought, with suffocating soil.    It is a wee bit succulent, has rugged leaves, has red coloration which may be sunscreen,  and has padded little pea-sized capsular toothcup fruits.   The flowers may or may not have petals, that’s odd, and it can sometimes, or perhaps predominantly, set seeds without benefit of outside pollination, a handy trait in a lonely pioneer.  The pollen-making anthers can break off and adhere to the pollen-receptive stigmas in the same flower assuring self-pollination emphatically.  The roots tolerate saturated mud.

That is all well and good, although perhaps unthrilling.  The magic is in the seeds, as Dr. Graham related.  The electron microscope photos below are from her 1985 publication.

The seeds are  packed a couple hundred per fruit.   They float, and have a special mechanism to do it well:  On one side of the seed there appears a small puffed up beer belly, a flotation device, which collapses when the seed dries.

Seeds photographed today.  The one on top is dry.  The one on the bottom is moist,  the puffed out float on the left. with light shining through.   As the seeds take on water out pops a bubble as seen lower right.

Ammannia seed showing the pufferbelly.  Photo from sources noted in text.

Even weirder, there are hairs on the inside of the seed coat, wrongside-in.  When the coat is moistened the hairs pop outward to become spikes like the antennae on Sputnik, where they may help water enter the seed.

Seed hairs moistened and sticking out.  Photo source mentioned in text.

The moistened seeds become a little sticky, which may help them grab hold to a final sprouting site, or may help them cling to a bird’s leg en route to the next aquatic environment.    The seeds are willing to germinate in a few days under favorable circumstances,  and if things aren’t optimal some are patient and tough, reportedly germinating from dried museum specimens 27 years old.

Sabal palmetto

Arecaceae, the Palm Family

Sap Beetle  Brachypeplus glaber

In the horticultural world vertical gardens became faddish a few years ago.   Nothing new there:   Cabbage Palms invented the concept, some of their trunks being vertical jungles, although other individuals can be bare and clean.   Many Cabbage Palms retain  broken-off leaf bases which turn into hundreds of little natural flower pots filled with spongy detritus.  Somewhere I read a list of around 60 plant species occupying Cabbage Palms, merely in one locality.  Some of the hangers-on are rooted on the ground and climb; others root on the palm itself, especially in those fertile leaf bases.

It is fun to walk and gawk at Cabbage Palms to see who is hanging around, and far more fun to wonder about the interactions among the species.   What nutrients, or toxins,  or hormones from the plants perched up high  wash down the trunk and suppress, or favor, species lower on the totem pole.  Some species may use allelopathy (natural herbicides) drizzling down the trunk to discourage competitors taking hold below.  The nutrient cycling patterns would probably amaze, if only we knew.

Corkystem Passionvine enjoying the palm trunk.

The species distributions up and down the trunks do not seem random, although unraveling suspected patterns may be complex or subtle.  Cabbage Palm ecology runs deeper than meets the eye.  The tree has a lot of hidey-holes, and its microscopic life is no doubt a realm of secrets.   The micro-hideaways are where we are headed now, thanks to a team of entomologists.

Honkin’ big hanger-on…Strangler Fig on the Cabbage Palm.

In 2014 Andrew Cline and collaborators explored a remarkable multi-species ecological web on Cabbage Palms.   Virtually everything I’m about to relate comes from their research, linked below.

Join me now at the senescent flower stalk bases still held on the tree.  Any suburban homeowner dragging the fallen inflorescences from their St. Augustine lawn can see layering around the stalk bases.  During yard cleanup however, we may miss all the fun in the layers, the lair of a sap beetle, Brachypeplus glaber, found in this niche essentially exclusively.  Oh-no, a “sap” beetle!   Does it suck sap and disrespect  our state tree?  No, apparently not, its diet is more complex, and the beetle perhaps even benefits its palm host whose flower stalks are the insect’s entire life-bringing universe.

CLICK to see the beetle

Enter a third species into the plot:   The palmetto scale insect Comstockiella sabalis sheds its skins.   Our sap beetle eats the skins in a handy act of recycling.   Great , now move on:

Now come the fungi.   The beetle has a tight relationship with a yeast, Meyerozyma caribbica.   The beetle, including its larval stages,  lives among the yeasts, eats them, and apparently hosts them as internal symbionts.   The same yeast is a known digestive helper in other insects. The entomologists suspected the yeast to be so potently antifungal  as to be of potential medical interest.

Yeasts are not the only important fungi in the story. The main diet of our sap beetle is filamentous fungi, particularly from the genus Fusarium.  Somehow the yeasts seem to help the beetle deal with the Fusarium.  Maybe they constrain it to a dietary level rather than allowing the pathogenic fungus to overwhelm the inflorescence too rapidly, destroying house and home, although that is 100% my speculation.

Fusarium fungi are plant pathogens, and anything that eats the Fusarium or suppresses Fusarium  might be defenders of the palm.

The tale of the sap beetle et al. can lead to just one “sappy” conclusion.  You guessed it.  Here we have a case where an insect and its yeast associates could protect the tree at its vulnerable growing crown right where infective fungi are most unwelcome.   Would residential applications of insecticides and fungicides disturb an intricate and possibly valuable beete-scale insect-yeast-palm-Fusarium microcosm?    And, by the way, where does that little ecoweb go when you “hurricane prune” a Cabbage Palm’s crown down to just a few leaves?

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A few species hanging around on Cabbage Palms

Algae and Cyanobacteria

Asian Sword Fern

Balsam-Pear

Boston Fern

Cowpea

Creeping Cucumber

Golden Polypody Fern

Grapes

Laurel Fig

Leafy liverworts

Lichens

Mosses of various species

Passionvines

Poison Ivy

Shoestring Fern usually with the moss Octoblepharum

Smilax

Strangler Fig

Tuberous Sword Fern

Virginia Creeper

Whisk-Fern (Psilotum)

Today’s primary source:  CLICK

Nature abhors a vacuum, including  muddy shores freshly exposed by the seasonal retreat of erstwhile shallow ponds.  Exposed barrens spell opportunity for ambitious pioneer species.   Colonization happens fast.  To meet plants you otherwise seldom encounter, don your boots and don’t sink in chin-deep.

There are no pre-existing competitors on new mud.  All newcomers can stake a claim.  Nobody is competitively excluded, so diversity abounds.  Let’s see, in the postage stamp mudhole I explored today I recall seeing (running out of fingers and toes) over 20 plant species.

Seedlings rising with no competition yet.  The last owner of that marine seashell was probably 15,000 years ago.

Who’s first to settle?  Floating plants carpet the receding water and are the first settlers, although the species composition shifts substantially.   The pudding-dwellers arrive for the most part floating as whole plants, or as little breakaway pups, or as fragments, or as seeds or spores.  The mud community is far more diverse than the species readily spotted afloat.

Green lowlifes on smelly mud take me back 470 million years to when plants originally strode forth from water to land.  Standing on the mud today was a window into pre-pre-history.  Look who we find, at least two examples of the most primitive still-existing plants, liverworts, straight out of a museum diorama.   I’ll bet today’s liverworts are almost unchanged from the first terrestrial plants, not counting bacteria and algae.

Liverwort Riccia fluitans. Welcome to the time machine.  Bet it looked the same in the Ordovician Period.

Liverwort Riccia cavernosa.  Do the cavities facilitate gas exchange?  Any symbionts in there?   I’ve seen a lot of diatoms on/around this liverwort, but have no idea if that means anything.

The real fun is seeing who the castaways are and their adaptations to the mud world.  What are the facts of life on quicksand?  It is sopping wet, unless the sun bakes the surface dry.    The habitat is too suffocatingly soggy to invite extensive roots.    It smells like sulfur.   Nutrient acquisition must be a challenge.

At least one resident brings its own nutritional assistance.  The floating fern Azolla has folded into its leaves symbiotic nitrogen fixing Cyanobacteria, microbial fertilizer factories.   It can have all the nitrogen it wants.   The other floater in the photo below, Salvinia, has every third leaf modified into a big nutrient mop no doubt able to help with the fertilizer problem in its own fashion.

Floating ferns love this stuff!  Salvinia with the big hairs on the right.  Azolla is on the left, with its internal Cyanobacteria.

The next rain spells doomsday for these precarious species, although each is ready for rainageddon in its own way.  They arrived floating, and can depart the same way, no problem?  What about those who came by seed and need to make new seeds?  They work fast.  The Pentodon in the photo below can bloom and fruit while still mere baby seedlings, not a moment to waste.   After that safe start,  the longer they live the bigger and more fecund they can be.

Precocious Pentodon, flowering as a seedling.

The Ceratopteris ferns, water sprites, can float and make bulbils to disperse as clones, and even better, they mature from spores to reproducing adults in as little as three months to complete their sexual cycle.

Returning to seeds, one way to win a race is speed, as we just discussed, but there’s another way… a head start like the Nebraska Sooners.  Barnyard Grass, Echinochloa crus-galli,   jumps the gun by having the rare ability for its seeds to germinate in the absence of oxygen still submerged or buried in stinking mud.  That is why this grass is a pest in rice paddies.

Another response to re-rising water is to live with it. The Southern Marsh Yellow Cress, Rorippa teres,  sprouts all over the mud.  Not only does it flower and set seeds early in life, it can probably also live submerged if its relatives are a good measure.  Although I do not have data on this species per se, some of its close kin have survived and grown during underwater tests as long as three months.  Let it rain!

Rorippa

What do we have in common with Charles Darwin?   Wondering about the weird and beautiful Green Alga Spirogyra doing the hokey pokey, moving all about, a little surprising in a filamentous photosynthetic true alga.  What’s up with that?

If Darwin couldn’t figure it out, I can’t.  Perhaps there is no function to it, with the movement being a byproduct of growth?  Check it out and go figure:

See the Spirogyra in action in the brief footage below.    The video has been sped up 10X:

CLICK HERE   to see what Darwin saw (The tiny dancers are varied aquatic microbes.)

These freshwater algae have the world’s oddest chloroplasts, twisted like a ribbon running the entire length of each cell.  It must be a good arrangement, as there are 400 different species, having anywhere from one to many helical ribbon chloroplasts per cell.    We ask again, why?   It looks like the spiral shape might be a consequence of the overall cell growth pattern.  The cell wall grows in a helical pattern, and the shape of the chloroplast conforms.   Like a spring, it is stretchable…a “plus” in a cell with the rare condition of each chloroplast running the length of the cell.

Those thickenings you see in the green chloroplasts are called pyrenoids (PIE-reh-noids). They are points of starch formation and storage.

Sometimes an algae-filled pond has a different look at the end of the day as opposed to dawn.   Some algae and so-called blue-green algae rise and fall on a daily cycle, sinking during the night and bobbing to the surface during the day.   In Spirogyra the simple and probably partially accurate explanation is that  during the day oxygen from photosynthesis collects in the algal mat, causing it to float upward.  That serves the alga well by placing it above the competition for sunbeams.

At night oxygen loss diminishes buoyancy, and the mat sinks.    I think I’ve seen the mat rise sooner under sunny conditions, delayed by shade.    You can see it too below.   The Spirogyra you’ll see is on my back porch in a closed plastic bottle about a foot tall.  It yo-yos up and down daily.    The rise recorded in the short time-lapse video below was in bright sunshine.    It resinks in the dark after my bedtime.  The dark bodies dancing around are time-lapse snails.

CLICK HERE to see the Spirogyra rise up