#cleistogamy

The Hidden Flowers of Viola

Violas keep a secret hidden below their foliage. Sometimes they even bury it shallowly in the soil near their roots. I suppose it’s not a secret really, just something out of sight. There isn’t a reason to show it off, after all. Showy flowers are showy for the sole purpose of attracting pollinators. If pollinators are unnecessary, there is no reason for showy flowers, or to even show your…

A new form of seed dispersal has been described. It involves birds but not in the sense we traditionally think. Everyone understands how effectively birds disperse seeds contained in small fruits such as berries, or as barbs attached to their feathers. It took finding an out-of-place patch of Japanese stiltgrass (Microstegium vimineum) for lead author Dr. Robert Warren to start looking at bird dispersal in a different light. 

While working in his yard, he noticed a patch of Japanese stiltgrass growing out of a window planter some 6 feet off the ground. Japanese stiltgrass can be highly invasive but its seeds aren't adapted for vertical dispersal. However, it does employ a mixed mating system composed of outcrossing flowers at the tips of the spikes along with cleistogamous flowers whose seeds remain on the stem. Taking out a ladder, Warren discovered that the grass was growing out of a bird nest. It would appear that stiltgrass stems containing seeds were incorporated into the nest as building material and then germinated the following year. Thus began a deeper investigation into the realm of nest seeds.

Teaming up with researchers at Yale and the United States Forest Service, they set out to determine how often seeds are contained within bird nests. They collected nests from 23 different bird species and spread them over seed trays. After ruling out seeds from potential contamination sources (feces, wind, etc.), they irrigated the nests to see what would germinate. The results are quite remarkable to say the least.

Over 2,000 plants, hailing from 37 plant families successfully germinated. In total, 144 different plant species grew from these germination trials. The seeds appeared to be coming in from the various plant materials as well as the mud used to build these nests. What's more, nearly half of the seeds they found came from cleistogamous sources. Birds whose nests contained the highest amounts of seeds were the American robbin (Turdus migratorius) and the eastern bluebird (Sialia sialis). These results have led the authors to coin the term "caliochory," 'calio' being Greek for nest and 'chory' being Greek for spread.

It has long been assumed that cleistogamous reproduction kept seeds in the immediate area of the parent plant. This evidence suggests that it might actually be farther reaching than we presumed. What's more, these numbers certainly hint that this otherwise unreported method of seed dispersal may be far more common than we ever realized. Whether or not plants have evolved in response to such dispersal methods remains to be tested. Still, considering the diversity of birds, their nesting habits, and the availability of various plant materials, these findings are quite remarkable!

Photo Credits: [1]

When garden plants go weedy, it doesn’t necessarily mean they’ve escaped the boundaries of our yards and invaded nearby natural areas or uncultivated spaces. While this is a concern for a significant number of ornamental plants, sometimes the weediness of a garden plant is experienced within the very yard or garden it was planted in. For some of us, such a plant’s weediness can turn us off from…

One of the earliest blooming wildflowers around my home is the violet.

It seems to have always been so since Shakespeare spoke of it being too early in blooming and therefore described it as ‘forward’.  It has been called modest for its short bloom cycle and for shying away low in the grass.  It was common for poets during the Georgian period to take woodland walks and after one those Leigh Hunt coined the term ‘shrinking violet’ in the poetry magazine The Indicator.  The violet does not produces seeds the way other flowers do.  Its reproduction through cleistogamy led the Elizabethans to attach a meaning of innocent, unspoiled love but its connection to love goes back to its origins in Greek mythology.

The Greek god Zeus fell in love, as he did frequently, with a young girl which made his wife Hera quite jealous – also a common phenomenon in their ‘relationship’.  To protect the girl, Io, from Hera’s anger Zeus changed her into a heifer but felt that grass was not good enough for her to eat.  He created the violet for her consumption.  From IO the botanical name of Viola was derived.  We often associate the flower with the color violet but violet used as a color was first recorded in 1370.  The virginal love in Greek mythology and during Elizabethan times seems quite appropriate since the color violet, in spectral analysis, is a true color while the color purple, with which it is often used interchangeably, is a mix of red and blue.

The scent of violets was employed in English funerary rites ostensibly for the same reason as rue and rosemary – that of remembrance.  The real reason for tossing these flowers into the grave was to protect ‘the mourners against poisonous exhalations from the cemetery’.  This may have come from Greece or Rome as the Greeks concealed the body with violets and placed them on graves.  These facts are from a lovely book published in 1911 by Charles M. Skinner – Myths and Legends of Flowers, Trees, Fruits and Plants   Other such facts include:

Among the flowers on which the shadow of the cross fell on the day of the crucifixion was the violet, and, like others in that shadow, it drooped in sorrow, thereby tokening its consecration in Christian services.  Its color is suggested in the purple of church mourning and the wearing of amethyst jewels by persons in orphanage or widowhood.

and

Napoleon was known as Corporal Violet because this was his favorite flower, and when sent to Elba he declared that he would return when the violets bloomed…..so there was a wonderful display of violets when he re-entered Tuileries.  It was much worn during his reign, and came to be so well known [sic] as his emblem that on the restoration of the Bourbons it was treasonable to wear it in public or even carry it in bouquets.

In Germany it was still a custom, at the time the above book was published, to ‘adorn bridal beds and cradles with it, a practice extending back to the Celts and the Greeks’.  In the nineteenth century it was grown and harvested, especially along the French Riviera, for making perfumes.

Not only has the violet been cherished for its sweet aroma but it is eaten as well.  The flowers are sugared as well as being used as a garnish for puddings, broths and other dishes.  They are purported to be good mixed with lettuce and onions in salads and “a dish known in England as vyolette consisted of the flowers, boiled, pressed and brayed with additions of milk, rice flour, and honey.”

Victorians, in their fondness for associating meanings with different flowers, attached to it the characteristic of faithfulness.  Perhaps that is one reason it has been widely used in literature although under various aliases.  Examples of other names are “Heart’s Ease” (Robert Herrick’s poem ‘How Pansies and Heart’s Ease Came First’),  Love-in-Idleness (Shakespeare’s ‘A Midsummer Night’s Dream’), and  Pansy (William Wordsworth’s ‘Ode: Intimations of Immortality from Recollections of Early Childhood’.  There are likely more literary references under its real name – Ophelia in ‘Hamlet’, Percy Bysshe Shelley’s poem ‘On a Faded Violet’,  Sir Walter Scott’s verse ‘The Violet (The Fairest Flower), and William Wordsworth’s ‘Lucy’.

I’m certain there are many more references and descriptions of it in literature.  If you have some to add please note them in “Leave A Reply” with them at the bottom of this page.

So we are familiar with violet as a color and associate it with the flower of the same name.  But not all violets are ‘painted’ by nature in that hue.  Below are violets – some more ‘violet’ than others. (William Cullen Bryant knew this as he wrote a poem titled “The Yellow Violet”.)

  Southern Wooly Violet – Viola villosa

Common Blue Violet – Viola Sororia

Common Blue Violet Viola Sororia

Halberd-leaved Yellow Violet Viola hastata

Sweet White Violet – Viola Blanda

Sweet White Violet – Violet Blanda

Marsh Blue Violet Viola Cucullata

Marsh Blue Violet Viola Cucullata

Great Spurred Violet – Viola Selkirkii

Great Spurred Violet – Viola Selkirkii

Pale or Cream Violet Viola striata

Pale or Cream Violet Viola striata

Pale or Cream Violet Viola striata

Pale or Cream Violet Viola striata

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In the wild, plants are not always found growing under ideal conditions. Often, many plant species find themselves on the fringe of their habitable range. Other times, pressures like trampling or grazing cause a plant to expend a lot of energy trying to recoup for lost resources. If a plant growing under these conditions is to successfully reproduce, it has to sometimes stake its bets on self-fertilization. 

The evolution of special flowers that never open has arisen in many different plant families. These permanently closed flowers are known as cleistogamous flowers. These are not always produced as a result of a direct environmental stress, however, and their persistence throughout so many different plant families is a bit of a puzzle to evolutionary biologists. How and why are these mixed mating systems maintained in a plant population? There must be selective advantages to both.

It has long been thought that plant populations should only stably exist as either fully opened, chasmogamous flowers, or fully closed, cleistogamous flowers. The existence of many species in which both forms exist on the same plant really threw a wrench into that hypothesis. Some examples of plants that possess such mixed mechanisms can be seen in genera such as Impatiens, Viola, and Utricularia. 

In the cases that have been studied, it was shown that cleistogamous flowers produce healthier seed with higher germination success than those of an openly pollinated chasmogamous flowers. It has also been shown that the production of cleistogamous flowers is much more economical for the plant. If flowers never open and never have to attract pollinators, then the plant doesn't need to waste energy on the production of petals, color, nectar, etc. This way, more energy can be pumped into seed production. 

The flip side to this mating system is that cleistogamy produces no genetic diversity. The plant is more or less cloning itself with every seed. This is okay if the plant is growing under challenging conditions. If the parent was able to survive long enough to reproduce then it obviously has the genetic make-up that is fit enough to survive such conditions and now, all of the cloned offspring do as well and thus all copies of its genes made it into the next generation. It is neat to think that plants kind of have this insurance policy built in to their reproductive strategy.

PHOTO NOTE: I found the picture of cleistogamous violet flowers on the following blog. It is not my picture! Please check out the blog for more!

source: http://blog.chestnutherbs.com/even-violets-need-a-plan-b

Further Reading: 

http://www.amjbot.org/content/96/11/2074.full.pdf+html?sid=41c1503d-23a8-40f8-93bf-8d849be7edec

http://www.jstor.org/discover/10.2307/1936588?uid=3739256&sid=21102186350373