FIELD PANSY

Viola arvensis

Violet Family [Violaceae]  

month8apr month8april month8may month8jun month8june month8jul month8july month8aug month8sep month8sept month8oct month8nov

status
statusZarchaeophyte
flower
flower8bicolour
flower
flower8white
inner
inner8yellow
morph
morph8zygo
petals
petalsZ5
type
typeZspurred
stem
stem8square

20th Aug 2011, arable field, Swettenham, Cheshire. Photo: © RWD
An arable weed, here growing amidst a crop of Mangel-wurzel.


7th Aug 2007, Arable Fields near Rufford, Lancs. Photo: © RWD
Several sturdy specimens growing amongst Dead-Nettles.


20th Aug 2011, arable field, Swettenham, Cheshire. Photo: © RWD
Flowers extremely variable in size, shape and colour, but always drooping downwards suddenly and at a steep angle.


7th Aug 2007, Arable Fields near Rufford, Lancs. Photo: © RWD
Upright on sturdy square stem, leaves long, lanceolate, slightly toothed.


7th Aug 2007, Arable Fields near Rufford, Lancs. Photo: © RWD
Leaves narrow, lanceolate, bluntly toothed, and rounded at the tip come off single, or in pairs, from a stiff square upright stem.


30th July 2009, Arable Fields near Kingsley, Cheshire. Photo: © RWD
Un-opened flower head on crooked square stem surrounded by five slightly hairy sepals pointed ready to hinge open.


20th Aug 2011, arable field, Swettenham, Cheshire. Photo: © RWD
Petals still in-rolled, not fully opened up.


7th Aug 2007, Arable Fields near Rufford, Lancs. Photo: © RWD
Five white petals, biaxial (zygomorphic) symmetry, rear two petals overlapping. Middle pair fringed in centre. Three slightly hairy sepals arranged in an equilateral triangle behind the flower; two more pointing vertically downwards. Flowers may or may not have yellow marks and purple lines like cats whiskers on lowest petal, often due to hybridization with Wild Pansy. The most definitive identifying feature is that the 5 sepals behind are visible from a full frontal view and that they are longer than the petals (shorter and tucked away, hidden from the front on Wild Pansy)


7th Aug 2007, Arable Fields near Rufford, Lancs. Photo: © RWD
Flowers are suspended singly from a 'Swans neck' crook in the flowering stem, which here is deeply grooved and tinged purple.


20th Aug 2011, arable field, Swettenham, Cheshire. Photo: © RWD
Square flower stalks. Sepals tinged blue-purple like sheet steel does after heat-treatment.


30th July 2009, Arable Fields near Kingsley, Cheshire. Photo: © RWD
Fruit developing within.


20th Aug 2011, arable field, Swettenham, Cheshire. Photo: © RWD
The stipules which emerge below branches resemble leaves with their large and long terminal lobe which itself is lobed or roundly-toothed and are deeply cut (the bottom 'leaf and leaflets')


Some similarities to : Other Pansys and Violets especially Mountain Pansy (Viola lutea).

Hybridises with : Wild Pansy (Viola tricolor) which itself comes in 2 sub-species: Wild Pansy(Viola tricolor ssp. tricolor) which has three colours (violet, white and yellow petals and Sand Pansy (Viola tricolor ssp. curtisii) which has bi-coloured petals, either white and yellow, or pale-blue and white. The hybrid between Wild Pansy and Field Pansy being called Viola × contempta.

Your Authour thinks it very strange that books seem not to mention the square stems, which are square at least where the flower is.

Habitat : Farmers arable fields on light well-drained sandy soils and any place where the soils are disturbed regularly like gardens (except ours.

Wild Pansy is an archaeophyte and grows as a weed on arable land and on waste ground, to be found throughout most of the UK.

VIOLAXANTHIN CYCLE

PROTECTION FROM EXCESS SUNLIGHT


A yellow to orange pigment, violaxanthin (or Zeaxanthin diepoxide) [not to be confused with Vioxanthin, another coloured compound found in some Lichens) is present in Pansies (such as Yellow Pansy). It is a di-epoxide xanthophyll, and it protects plants containing it from photo-oxidative damage by minimizing the formation of dangerous oxygen radicals. When the light absorbed by plants exceeds the capacity of the photosynthesis machinery to convert it to sugars etc, then the extra light goes towards de-epoxidizing violaxanthin to Zeathanthin in a 2-step process via an intermediate antheraxanthin which has just a single epoxide group. This conversion is reversible - being called the violaxanthin cycle. This protective mechanism also operates in Thale Cress and other plants. The conversion of violaxanthin to zeathanthin is mediated by an enzyme called violaxanthin de-epoxidase which is activated by the incidence of strong sunlight and the presence of Ascorbate (Vitamin C) in a low pH environment. The effectiveness of this protective mechanism is thus limited by the availability of ascorbate and if lacking for any reason then the plant may suffer stress under strong sunlight.

In low-light the reverse process happens, mediated by a different enzyme, zeaxanthine epoxidase which adds the epoxide group to both Zeaxanthin and antheraxanthin in readiness to protect the plant when the sun shines strongly again (up-arrows).

Antheraxanthin is an intermediate neutral-yellow carotenoid with just a single epoxide group (Violaxanthin possesses two; Zeaxanthin none).


  Viola arvensis  ⇐ Global Aspect ⇒ Violaceae  

Distribution
 family8Violet family8Violaceae

 BSBI maps
genus8Viola
Viola
(Violets)

FIELD PANSY

Viola arvensis

Violet Family [Violaceae]  

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