categoryZFerns Ferns List 

COMMON POLYPODY

Polypodium vulgare

Polypody Family [Polypodiaceae]  

Spores Ripe:
spores8apr spores8april spores8may spores8jun spores8june spores8jul spores8july
Fronds:
fronds8apr fronds8april fronds8may fronds8jun fronds8june fronds8jul fronds8july

category
category8Ferns
status
statusZnative

11th Sept 2009, War Memorial, Boot, Cumbria. Photo: © RWD
On a granitic dry-stone wall.


11th Sept 2009, War Memorial, Boot, Cumbria. Photo: © RWD
Has blunt leaflets.


11th Sept 2009, War Memorial, Boot, Cumbria. Photo: © RWD
By transmitted light, sori visible on upper parts of plant as shadows from the far side.


11th Sept 2009, War Memorial, Boot, Cumbria. Photo: © RWD
Leaflets zig-zag alternately tapering up the stem. Lower leaflets curled forwards. Pronounced mid-leaflet veins.


11th Sept 2009, War Memorial, Boot, Cumbria. Photo: © RWD
Sori make visible bumps on the upper surface.


11th Sept 2009, War Memorial, Boot, Cumbria. Photo: © RWD
From the obverse, sori in round gatherings, in two closely interleaved rows up the leaflet.


11th Sept 2009, War Memorial, Boot, Cumbria. Photo: © RWD
From close up spores look like golden sand grains.


11th Sept 2009, War Memorial, Boot, Cumbria. Photo: © RWD
Which have a darker mark.


Hybridises with : Southern Polypody (Font-Quer's Polypodium) and with Intermediate Polypody. From the BSBI distribution maps for the possible hybrids, their presence amongst these photos can be discounted.

Some similarities to : Western Polypody and Southern Polypody.

EXTREMELY SWEET STEROIDAL GLYCOSIDES


Both Osladin and Polypodoside A are extremely sweet saponins or sapogenin steroidal glycosides that occur in the roots and rhizomes of both Common Polypody (and in Liquorice Fern which is also called Sweet Root (Polypodium glycyrrhiza), but which is not found in the UK). Compared with a 6% w/v aqueous solution of Sucrose, Polypodoside A is 600 times sweeter than sugar. But as with most other intensely sweet substances, it is so sweet that the sensation of sweetness lingers for over an hour. A direct relative of Polypodoside A, Osladin, is one of the sweetest known natural steroidal glycosides, variously reported as being 500 or 3000 times sweeter than sucrose.

Whether any particular steroidal glycoside is intensely bitter or intensely sweet depends upon both the identity and arrangement of the glycosides, and their stereochemical juxtapositions.

There are about a dozen known intensely sweet steroidal glycosides known, one of which being Glycyrrhizin which occurs in Glycyrrhiza glabra, and is the well known 'spanish' liquorice root. Other sweet steroidal glycosides (some of which may be synthetic) are Mograside V, Arbruside A (from Arbus precatorius); Stevioside and Rebaudioside (from Stevia rebaudiana, and Baiyunoside (which occurs in Phlomis betonicoides), but none of these plants are to be found within the UK.

Polypodoside A is chemically: Polypodogenin-3-O-α-L-rhamnopyransyl-(1→2)-β-D-glucopyranosyl-26-O-α-L-rhamnopyranoside.

Osladin is 22R,26R-Epoxy-6-oxo-25S-5α-cholestan-3β,26-diol-3-O-[α-L-rhamnopyranosyl-(1→2)-β-D-glucopyranoside]-26-O-[α-L-rhamnopyranoside]

The stereochemistry is important for taste. Excepting the stereochemical differences, the main difference between Osladin and Polypodoside A is the double bond on the steroid moiety which is absent on Osladin (bottom, centre).


  Polypodium vulgare  ⇐ Global Aspect ⇒ Polypodiaceae  

Distribution
 family8Polypody family8Polypodiaceae

 BSBI maps
genus8Polypodium
Polypodium
(Polypodys)

COMMON POLYPODY

Polypodium vulgare

Polypody Family [Polypodiaceae]  

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