Wind-Pollinated Oaks

Live Oak by John Badford

John and I worked today mostly on Oaks in Halpatioke Park in Stuart, Florida.   Many Oaks (and Pines) are shedding pollen now into the air, as we  allergy vics know so well.   Being that wind-pollinated plants are asserting themselves today,  let’s not talk about the birds and the bees, but rather the nerds in the breeze. Achoo.

Flowering plants are “all about” animal-mediated pollination.  Although there remains a ton to learn about the early evolution of flowering plants,  the standard perception is that flowering plants evolved from wind-pollinated ancestors, that their raison d’être is to offer attractants and rewards to creatures in exchange for symbiotic pollen transfer.   Yet over 10 percent of flowering plants are wind-pollinated. (I wonder if that will increase as we drive insect pollinators into oblivion.)

Myrtle Oak male catkins releasing pollen,  by JB

Wind-pollinated flowers represent a return to wind from insect-pollinated ancestors, that is, wind, then insects, then back to wind.   Why go retro?  Botanists estimate that the about-face has happened in over 60 instances.    Sometimes wind-pollination works better than bugs and birds, most obviously in circumstances where creature-based pollination is unreliable, such as harsh habitats and wide open spaces.

Wind-pollination is comparatively rare in tropical forests with high plant species diversity and plenty of birds, bees, moths, bats, and butterflies.  Wind-dependence becomes more prevalent in temperate and cold regions, and in places with high concentrations of relatively few plant species.    It would be pointless to dump pollen onto the wind where you are surrounded by different species.   But, by contrast, wind works if most of your neighbors are the same species as you, such as a prairie or marshland.  Not surprisingly then, most grasses and sedges are wind-pollinated.

Laurel Oak today, male catkin loaded with pollen ready to spew.

Many temperate- and cool-region trees are windy.  With these,  seasonality may matter.   In the early spring the temperate trees have no leaves to block pollination, yet insects and birds may still be scarce, and why compete for animal services when the wind is free, unlimited, and continuous nice and high in the treetops?   Why make nectar, make pretty petals, and have bees steal pollen if not necessary?  Why have a motorboat when a sailboat needs no gas?  Wind-pollinated trees include hickories, walnuts, chestnuts, ashes, poplars, and today, oaks.

Many wind-pollinated plants avoid airborne self-pollination by existing as separate male and female plants, although individual Oaks have both flower types in the same tree.   The male flowers are in dangling clusters called catkins well designed for shaking oodles of pollen out into the zephyrs.

The female flowers, fewer and solitary or in small groups, are tiny acorns-to-be with big stigmas acting like catchers’ mitts to snag the pollen from the air.

Female Laurel Oak female flower. Microscope view. Call it a future acorn, with the future acorn cap at its base.   The big dark-colored stigmas catch the pollen off the wind.

 

Myrtle Oak and Its Micro Mites

Quercus myrtifolia

Fagaceae

John and I sought ecological enlightenment today among the oaks of Halpatioke Park in Stuart, Florida, the home of several oak species, from massive gnarled Live Oaks to knee-high “Dwarf Live Oaks.”   In-between, Myrtle Oak, is the center of today‘s attempt to interpret little things.  Around here, Myrtle  Oak is a a scrub species, usually shrubby or a small tree, potentially fairly good-sized but rarely so..  Its overall range is most of Florida and the coastal regions of nearby states.   This species harbors mites.

This and the following three photos by John Bradford.  All Myrtle Oak.

Male flowers in catkins.

Mites are so small we can scarcely see them, even with magnifiers, which might be why mite-plant relationships are mite-y under-studied.  Gardeners may think of mites as pests, which is true enough, and some cause weird growth irregularities in their botanical hosts, such as bizarrely deformed fruit on Black Olive trees.   But that is not the whole truth and nothing but the truth.  Suppose you’re a plant species plagued by herbivorous mites, what is the best protection?

Predatory mites of course, fight fire with fire, and it turns out that many plant species provide homes for their guardian predators, which is not to say every aspect of mite-plant symbiosis is understood.  Some good mites eat fungi.  Speculators have speculated that mites may benefit host plants by providing a foliar feeding of their nitrogenous waste.   I dunno about that, but it is interesting that the Myrtle Oak domatia seem to fill up with organic matter.

Myrtle Oak hairy armpit domatia on underside of leaf where veins join.

The same with apparent accumulation of organic matter.  Looking lived-in.

Whether or not the little guys make enough manure to matter, plants do provide fine accommodations for “good” mites.  Such “domatia” (think domicile) come in three forms:  leaf pits (as in white mangroves and in buttonwoods), caves under veins (as in grapes), and furry bushes made of tangled plant hairs  where leaf veins join, as in today’s oak and others.  The domatia in Myrtle Oak are conspicuous beneath the leaf.

If you flip over a Myrtle Oak leaf and spy with a hand lens (very) patiently you can spot tiny mites on the prowl, sometimes flushed from a domatium like a bunny from a bush.

CLICK HERE for a quick glimpse of a Myrtle Oak mite on the move.

Those who study mites have found that even “bad” mites have domatia too.   Maybe they merely stole them, but other observers have a more interesting explanation…that to sustain good predatory mites the plant has to offer edible “bad” mites to pay the guardians in red meat.   The plant may adaptively tolerate and even shelter prey for the hunters.

 

Linden-Leaf Hibiscus and Its Buggy Friends

Hibiscus furcellatus

(Hibiscus is an ancient name.  Furcellatus means forked, as we shall discuss)

Malvaceae

Monsoon deluges and fascinating meetings combined to complicate botany fieldtrips this week, although today’s sunny skies lured me to the Delaware Scrub in Jupiter, Florida, into the midst of an old friend in full bloom, full fruit, full bud, and  full cooties.  Today’s blog is a bug-centric revisit to Linden-Leaf Hibiscus.

First and foremost, this is an ant plant.   The buds, flowers, and pods have big showy nectar glands on the outside.   These draw ants by the gazillions, who jostle rudely for a moment at the trough.  Presumably the ants protect the hibiscus from pests out to steal nectar, seeds, or other precious floral commodities.

Space mouse?  No–Hibiscus bud with two big nectaries, and with the forks showing.

It wasn’t just ants hanging around.  There came flies, ladybugs, camouflaged spider, and the orange creeps featured below.

The weird thing about this Hibiscus species is a ring of stiff forks curving up around the flower and fruit base.  Technically the forks are bractlets, that is, drastically modified leaves at the floral base.  Other Hibiscus have bractlets too, but in H. furcellatus they are oversized, stiff, and forked like a snake’s tongue.  They look like they could dispense nectar, but the visiting insects reject that notion.

Perhaps they are protective.  When the blossom is open the forks don’t seem to block anything, but earlier, they form a tight cage around the precious expanding bud.  The two tines on the fork spread across the top of the bud to thwart attack from above.   No beast can feast on that big tasty encaged bud.  Closed until we say so!

Fork cage around bud, orange.  Younger one to the left.

The cage goes through a yellow or yellow-orange phase.   I don’t know if that is significant, although maybe the colorful “false fruit” draws a bird’s eye long enough for the birds  gobble suspicious burglars loitering on the bud.  Just a guess.

The insect posse today included Cotton Stainer Insects boosting seeds from the ripe seedpods.  Cotton Stainers owe their name to their damage to cotton flower heads, and cotton is a close relative of Hibiscus.  All in the family,  although the little orange pirates abuse non-Hibiscus relatives  too.   The bugs poke their proboscis into seeds almost as big as they are.

Watch the Cotton Stainers conduct a raid CLICK

Likewise orange but not vegetarians, assassin bugs too were there to lunch upon some of the Hibiscus visitors.

 

Mighty Oaks from Little Toxic Acorns Grow

Quercus virginiana

Fagaceae

Live Oak by John Bradford

Today John and George explored Halpatioke Park along the South Fork of the St. Lucie River.  We experienced botanico-diversity, witnessing mighty Live Oak Trees supporting a dozen species of epiphytes from liverworts to orchids, mostly southern needleleaf bromeliads.   Nothing like mighty oaks to get a person thinking about little acorns.   Today’s blog required collusion.  Doing much of the research, John started it.  Or to step back further, Dee (see the blog authorship) was the ringleader.  Dee studies Scrub Jays.  Scrub Jays fancy acorns.  Dee and John started looking into acorn species preferences among the jays.   They’re the brains of this oaky operation.

An acorn is a wonderful little space capsule for an oak embryo.  Hard on the outside, loaded with food on the inside, and with self-defense.  It is the oak fruit, containing one lonesome seed.   The cute little cap is a cluster of tiny modified leaves, bracts,  not part of the fruit.

Acorns by JB. The cap is a leaf cluster.  The pointy tip is the style from the female flower whose ovary became the the acorn.

Acorns are loaded with nutrition appreciated by weevils, by birds especially jays, and by rodents, especially squirrels.    Weevils alone can destroy a substantial portion of an acorn crop.   Jays and squirrels feast on acorns, but there’s a tradeoff, the animals disperse surviving acorns in the process.

If everybody wants to eat you, you need protection.  The main anti-nibbling ingredient in acorns is tannin, as in tan your hide.   Tannins bind up the salivary proteins in the mouth and digestive systems of herbivores and they suppress microbes.   We exploit that ability to preserve leather.

The interesting thing John and Dee discovered is that tannin distribution is not even throughout the acorn,   especially in the Red Oak Group, defined below.   The critical vital portion of the embryo is toward the acorn’s pointy tip where the acorn concentrates tannins.    The more expendable portion is the cap end.    Creatures eating such acorns tend to reject, relocate, and maybe even bury, the nasty part which retains the ability to sprout.

The vital part of the embryo is toward the pointy tip.  In this photo see the base of the embryo, the future root, near the acorn tip.  It will pop forth soon, as shown in the following three photos.

Peek-a-boo

As germination progresses, the young root headed down and the young shoot headed up become displaced from the acorn with the food-rich seed leaves (cotyledons) remaining inside the acorn and continuing to feed the baby, as visible below.

The acorn with the cotyledons inside is to the left.  The young shoot rises toward the top left corner.  The young root in Live Oak develops a thickening, pointing to the lower right, presumably protecting the young tree from fire or other aboveground peril.

Much later, the root thickening enlarged. By JB.

Tannin is not evenly distributed among species.   The species in the Red Oak Group, locally including Myrtle Oak and Sandhill Oak, tend to have especially bitter acorns especially repugnant to distributors yet more likely to be only partially eaten non-fatally.   When animals bury acorns they are more often from the Red Oak Group.   Such acorns surviving storage are effectively relocated and planted.   They correspondingly tend to be slow to germinate.   Scrub Jays reportedly prefer such high-tannin acorns for caching, spotting them because they have less insect damage than the low-tannin alternatives.

The White Oak Group, including today’s Live Oaks as well as Chapman’s Oak and Sand Live Oak, tend  to have more-edible acorns probably more attractive to distributors yet also more susceptible to destruction.  These acorns tend to be dispersed less than the Red Oak acorns, staying nearer the parent tree, and germinating quickly.  Some years, mast years, the trees make acorns in such massive quantities that overmatch the nibblers.

Low tannin is why deer and humans prefer White Oak acorns.  Don’t try it.  Tannins are bad for you, and who knows what else is present.  Yet if you belonged to any of many acorn-eating cultures around the world you might have enjoyed acorns most often ground to flour, leached, and made into mushes, porridges, cakes, and breads.

Quercus geminata…the twins as in Gemini.  By JB.

Dig deeper:

https://www.sciencedaily.com/releases/1998/11/981126102802.htm

 

 

 

Why Does the Slash Pine Prune Itself?

Pinus elliottii

Pinaceae

 

John and I botanized and photographed today at Halpatioke Park in Stuart, Florida.  Great place for pines, and for thinking about why they shed their lower limbs.   Such self-pruning is not limited to  Slash Pines, but they are mighty good at it.  The trunk becomes bare below the crown as the crown rises.

The standard explanation is that discarding those flammable lower branches is protection from ground fires.    Ain’t sayn’ it ain’t so, but then again,  the party line strikes me as more intuitively easy to surmise than based on data.

I’ve heard other related notions, such as the lower limbs being too costly to maintain relative to their contribution to overall photosynthesis.   Also I’ve heard speculation that symbiotic fungi may faciitate severance.  Again, maybe, but those untested ideas don’t rock my world.

When leaves, and in some species twigs,  fall from trees they break off cleanly at a preset fracture point called an abscission zone.   Not so in Slash Pines.  The doomed branches seem to die slowly and decay on the parent tree, until they are sufficiently rotten to fall, blow, fragment, or be knocked off.  The breakage point can be anywhere from the trunk to 5 or 6 feet out.

Instead of worrying why the tree discards branches from a standpoint of what good it may do the tree, let’s shift our gaze to how it happens, and how a Slash Pine is vastly more prone to it than its broad-leaved neighbors.  Time for comparison.

Before we dare to compare, a useful fact:  as a woody stem ages its central region loses functionality, and the outer younger wood and associated tissues are where the vital action is. Remember that, inner regions kaput, outer layers lively.

Now  look closely in the photos below at the broadleaf Florida Privet disinclined to self-pruning.    The two photos show the main stem (left) with a branch diverging to the right, split open down the middle.     Notice that the  white fibrous wood of the branch is continuous with the young outer material of the parent main  stem.   The branch and the active wood of the main stem are the same wood.  Wood from the main stem arches out into the branch and sustains its life.

Florida-Privet keeps its branches.  The wood extending into the cut-off branch on the right is a continuation of the wood of its parent.  When one stops and the other starts is not clear.

Florida-Privet closeup showing the parent stem outer wood bending out and becoming one with the branch.

Now, by contrast, look below at the pine main branch and its side-branch, likewise split open.  The side-branch is mostly separate from the outer layers of the parent stem.   The side-branch resembles a spike driven into the core of the parent.  Its main connection to the parent is the parent’s aging inner tissues, declining and  choked by the expanding girth of the parent.    The hollow center of the parent stem is contiguous with the decaying center of the side branch.     Anchored in decline, choked,  and mostly independent from the lively outer layers of its parent,  the side-branch fails.

The pine side-branch, circled, plunges to the center of the parent-stem whose outer layers are not much integrated into the branch.   The parent is becoming hollow at the core (the dark regions) showing insect damage…the  death tunnel extends directly into the side branch. In the upper right corner the branch is separating from the outer layers of the parent-stem. In the lower right, the outer parental layers narrow down and mostly stop short of becoming a major component of the branch, looking like their expansion may even help gag the branch base.

If the increasing diameter of the parent stem helps doom the side branch,  in cases of all else being equal, such as two adjacent trees or two forks of one tree, you’d expect the branches to fail at about the same parent-stem diameters.   Notice that in the two photos below.

If the parent-stem dies and thus quits thickening, a side-branch below the damage  may then be spared and live on.  Examine the photo below.

Looks like the death of the parent stem gave the side-branch a stay of execution.

Let’s come back now to the notion that the self-pruning is an adaptation to rise safely above ground fires.  Having branches rot because of an anatomical quirk seems a roundabout way to achieve fire avoidance.   But we could turn the beat around…maybe pines thrive in places with ground fires because they lose their lower branches.   Perhaps the chicken came before the egg.

 

Why Do the Sunflowers Bend?

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

 

Swamp Fern has Three Tricks Up Its Stipe

Blechnum serrulatum (Telmatoblechnum serrulatum)

(Blechnon is  Greek for fern.  Serrulatum refers to tiny toothlets on the leaf margins. Telmato denotes wet habitats.)

Blechnaceae

Swamp fern by John Bradford

There’s nothing more enchanted than bright morning in a cypress swamp during the dry season.   The habitat is open, easy to navigate, bugless, and decorated with colorful lichens from rose to battleship gray, asters in bloom, and mossy hues a Leprechaun might recognize.

The biology is enchanting too, seeing cypress knees with spongy growing tips; seedlings seizing the day under the leafless canopy; northern needleleaf with ants; and a dozen plant species huddled on the bald cypress above the highwater line.

Northern needleleaf with ant

So many wonders, yet time and space force a choice.  Swamp fern looks like “any old” fern, so what’s swampy about it?   The fern shows at least three curious adaptations to life with its roots submerged some months and desert-dry other months.   Being equipped for both extremes give the species a competitive edge, in charge where purely aquatic plants would fry and where purely dry-land plants would drown. Sun or shade just fine.

Swamp fern. Two rows of spore cases beneath the toothy leaflets.

Wet and Dry Adaptation 1.   The leaf stalks have veins embedded among air pipes extending from the high dry leaves down into the intermittently submerged regions.

The leaf stalk cut and magnified.  The well protected veins are white, surrounded by the air pipes.

Wet and Dry Adaptation 2. When the fern perches on a bald cypress above the high-water line, the plant is not permanently an epiphyte unable to reach the earth.  Look closely…like a little banyan, it drops rhizomes and roots from its elevated base down along the cypress trunk and into the soil at the host tree’s base.

Swamp fern hanging on bald cypress.  The fern’s rhizomes and roots descend from the attachment point to the ground.  Some months they would be largely submerged.

Wet and Dry Adaptation 3.  This one requires speculative interpretation.  When the fern sits directly on periodically flooded mud it can build itself a pedestal made of a vertical cluster of slender rhizomes bound together into a spongy fascicle by a fibrous meshwork of roots.

Base of the fern (leaf stalks on top) rising from the black pedestal.

The pedestal lifts the fern above the flood when necessary, and looks like it collects debris and microbes in its network of nooks and crannies.  When the water is low, the pedestal becomes a reservoir of moisture and nutrients.

The pedestal is a mass of vertical rhizomes and roots all tangled together to make a tall sturdy sponge.

Among the blackened dead yet fibrous roots are living roots looking like they harvest water and nutrients from the spongy pedestal through which they creep.

Magnified view of living root creeping through the blackened spongy matrix of the pedestal.