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STRAWBERRY-TREE

STRAWBERRY TREE

Arbutus unedo

Heather Family [Ericaceae]

month8aug month8sep month8sept month8oct month8nov month8dec

category
category8Shrubs
category
category8Broadleaf
category
category8Evergreen
native
statusZnative
flower
flower8white
inner
inner8green
morph
morph8actino
petals
petalsZ5
type
typeZpanicle
type
typeZbell
stem
stem8round
rarity
rarityZrare

2nd Sept 2019, walled garden, Waterloo, Sefton Coast. Photo: © RWD
A native and evergreen shrub or tree which grows to 5m (and up to 11m).


2nd Sept 2019, walled garden, Waterloo, Sefton Coast. Photo: © RWD
With evergreen leaves which do not fall off in winter.


2nd Sept 2019, walled garden, Waterloo, Sefton Coast. Photo: © RWD
Leaves semi-glossy on upper surface.


2nd Sept 2019, walled garden, Waterloo, Sefton Coast. Photo: © RWD
Flowers creamy white (sometimes pinkish)in terminal panicles.


2nd Sept 2019, walled garden, Waterloo, Sefton Coast. Photo: © RWD
Leaves 4cm to 11 cm long, with a slight spherical curvature (in two planes).


2nd Sept 2019, walled garden, Waterloo, Sefton Coast. Photo: © RWD
Leaves have shallow forwardly-directed and blunt teeth. When open, the flowers are bell-shaped like those of Bilberry


2nd Sept 2019, walled garden, Waterloo, Sefton Coast. Photo: © RWD
stems often pinkish, especially the short bracts. Flowers (6-11mm) have a smaller reflexed opening where 5 petals reveal their presence, but for the rest of the flower the petals are fused into an upturned bowl shape.


2nd Sept 2019, walled garden, Waterloo, Sefton Coast. Photo: © RWD
Unopened flowers are half encased in short sepals which are more easily discerned on the naked flower where the petal(s) have dropped off together with the anthers leaving just the long style and stigma (left)


2nd Sept 2019, walled garden, Waterloo, Sefton Coast. Photo: © RWD
Short green sepals encase egg-shaped as-yet un-opened flowers.


2nd Sept 2019, walled garden, Waterloo, Sefton Coast. Photo: © RWD
The lampshade.


2nd Sept 2019, walled garden, Waterloo, Sefton Coast. Photo: © RWD
When opened the sepal teeth take the form of a pentagon


2nd Sept 2019, walled garden, Waterloo, Sefton Coast. Photo: © RWD
Looking up inside the constricted flower opening. Centre is a single style which protrudes from the slightly from the opening showing a small discoidal stigma (green at first, blackening).


2nd Sept 2019, walled garden, Waterloo, Sefton Coast. Photo: © RWD
Style with stigma in centre, 10 reddish anthers crowding around it within. Petals might be slightly green.


2nd Sept 2019, walled garden, Waterloo, Sefton Coast. Photo: © RWD
There are 10 pouch-shaped anthers with a round(ish) opening visible.


2nd Sept 2019, walled garden, Waterloo, Sefton Coast. Photo: © RWD
To better see the innards, your Author clumsily tore off half of the lampshade petal. Several anthers escaped during this process leaving just a few bag-shaped red-coloured pouched anthers with two fawn-coloured curved horns each. Stigma is pale-green, emerging from a pimpled pale-green ovary (which will become the 'strawberry-like' red fruit.


2nd Sept 2019, walled garden, Waterloo, Sefton Coast. Photo: © RWD
Inside of petal(s) has long white hairs.


2nd Sept 2019, walled garden, Waterloo, Sefton Coast. Photo: © RWD
Blackened style on stigma. Horned anther bags. There are long white hairs within the 'lampshade' petal(s).


2nd Sept 2019, walled garden, Waterloo, Sefton Coast. Photo: © RWD
The toothed sepals, ovary, stigma, style, nearly all of them green.


2nd Sept 2019, walled garden, Waterloo, Sefton Coast. Photo: © RWD
Leaf teeth barely toothed.


2nd Sept 2019, walled garden, Waterloo, Sefton Coast. Photo: © RWD
Underside of leaf, less glossy.


Some similarities to : Evergreen Spindle (Euonymus japonica) which also has similarly shaped semi-glossy evergreen leaves which also have shallow forwardly-directed teeth, and the flowers are also off-white greenish but they have four fully opened petals which are small and round, and four anthers between the 4 petals (rather than bell-shaped flowers held upside-down).

Uniquely identifiable characteristics : the strawberry-like fruit.

Distinguishing Feature :

No relation to : Strawberry (of any kind) nor to Strawberry Stonewort (Chara fragifera), Strawberry-blite (Chenopodium capitatum), Strawberry Saxifrage (Saxifraga stolonifera), Strawberry Clover ( ), Strawberry (Trifolium fragiferum), [plants with similar names from differing families].

The ripe fruits are red and 1.5 to 2cm across. Unripe pale-green, which progress through yellow and orange to end up at red. They do not look like strawberries because they are covered in conical pimples all over. At the opposite end to the stalk is a short black protruding stick; the remains of the stigma. They are not strawberries, just look a bit like them. The fruit only rarely occur on planted shrubs, they are more likely to appear on shrubs which are in warmer climes. The shrub flowers in autumn alongside fruits from the previous year, if any.

It is a native but a very rare [RRR] plant which grows in rocky ground in scrub and young woodland. It occurs mainly in ireland in South & North Kerry, West Cork, and County Sligo. It is only rarely naturalised (by birds) but when it is, it is found on chalk slopes or limestone slopes in Eastern Ireland, England, Wales and Jersey.

The fruits of Strawberry-tree contain several groups of secondary metabolites; some simple phenolics such as Gallic Acid, ProtoCatechuic Acid, Gentisic Acid, para-HydroxyBenzoic Acid, Vanillic Acid and meta-Anisic Acid (aka m-MethylSalicylic Acid), several flavonol glycosides such as the 3-O-glycoside of Quercetin and the 3-O-Rhamnoside of both Myricetin and Quercetin. Galloyl derivatives and Elagitannins present include TriGalloylQuinic Acid, TriGalloylShikimic Acid, Strictinin (an elagitannin) and the Rhamnoside of Ellagic Acid. Also present are proanthocyanidins ProAnthoCyanidin B1, ProAnthoCyanidin B3 and ProAnthoCyanidin B7 which are dimers based upon Catechin. GalloCatechin is also present.

There are also the AnthoCyanins Delphinidin-3-O-Galactoside, Cyanidin-3-O-Glucopyranoside, Cyanidin-3-O-Arabinoside and many other derivatives. The Vitamin E Tocopherols also feature widely in the fruits, as well as the related carotenoids  β-Carotene,     Lycopene and    Lutein.

SIMPLE ACIDS

The fruits also contains many simple organic acids such as Oxalic Acid, Malic Acid, Fumaric Acid, Lactic Acid, Citric Acid, Suberic Acid and Quinic Acid where the concentrations of each depend upon the ripeness of the fruits, and upon the country in which it is grown.


Lactic Acid is present in St Ivel Lactic Cheese, if that can still be purchased anywhere; your Author has not seen it in the shops for several decades. There are 2 optical isomers of Lactic Acid, the S- and R- forms. Lactic Acid (actually L-lactate) is produced within hard-working muscles as they metabolise glucose to produce work, but they must strive to rid themselves of it, otherwise muscle fatigue sets in. The bacteria Lactobacillus also produces Lactic Acid by a fermentation process. It is now also used in some commercial de-scalers and soap-scum removers by the detergent industry, for it is much more environmentally friendly that other (noxious) descalers. The polymeric form, PolyLactic Acid is used to make some biodegradeable plastics.

Oxalic Acid, by contrast, is a dicarboxylic acid, and is present in several plants with a highly astringent taste, such as Rhubarb where its concentration in the leaves (which contain much more than the stalks) is 0.52% by weight, but the highest concentration is found in Parsley at 1.7%. It is mechanically toxic in its crystalline form due to the needle-like crystals it forms called raphides, which puncture cell walls killing the cells. It is usually found as hydrated crystals, COOH)2˙2H2O. In its anhydrous state, due to hydrogen bonding, it exists as two polymorphic forms; one bonded in a linear string, the other in a planar sheet array.


Fumaric Acid is an unsaturated dicarboxylic acid isomeric with Maleic Acid (not to be confused with Malic Acid). Fumaric Acid is the trans form, Maleic Acid the cis-form. Fumaric Acid has a fruity taste. Found in species of Fumitory such as Common Fumitory (Fumaria officinalis) some bolete mushrooms, and lichens such as Iceland Moss (Cetraria islandica) It is used as an acidity regulator in foods and is designated E297. It is also used as a vinegar substitute, such as in 'salt and vinegar' flavour crisps. Use is also found as a mordant in the dying process. Fumaric Acid is practically non-toxic, indeed, it is used as a key intermediate in mammals (and all other aerobic organisms) during the TriCarboxylic Acid Cycle (KREBS cycle) - a metabolic pathway involving the recycling of OxaloAcetate, Malate, Fumarate, Succinate, OxoGlutarate, IsoCitrate, cis-Aconitate and Citrate and back to OxaloAcetate in a continuous circle, all the while consuming Adenoside TriPhosphate (ATP) as the energy source.

Malic Acid is an intermediate moiety in the Citric Acid Cycle (CAC) which is also known as the TriCarboxylic Acid Cycle aka KREBS cycle (ses above). It seems biochemists are just as prolific with alternative names as are botanists. See  Citric Acid Cycle. Malic Acid comes as two stereoisomers, L- and D- enantiomeric forms, but only the L-form is produced biologically. Apples are a well known source of Malic Acid, indeed, the Apple Tree genus (Malus) gives its name to malic acid, although it can also be found in many other fruits such as Blackberry, Grape, Blueberry, Apricot, Cherry, Quince, Pear, Peach, Plum, Quince, Rhubarb (in which the taste of Malic Acid is very pure). Like Fumaric Acid, it is also used as a vinegar-like flavouring in Salt and Vinegar flavour crisp under E296. It is also present in wine.


Citric Acid is present in most citrus fruits, such as Lemon, Orange and Grapefruit, hence the name, and is also used (mainly as the citrate salt), as a preservative in all sorts of tinned foods, even tinned tomatoes (which don't originally contain citric acid, so it makes them taste awful).

Suberic Acid (aka Octanedioic Acid) is another Dicarboxylic Acid, as are all shown here except Lactic Acid and Quinic Acid. Suberic Acid itself is a colourless crystalline solid used in the manufacture of plastics and in drug synthesis. It is found in Cork, the thick soft phellem layer of bark tissue usually derived from Cork Oak (Quercus suber). The cork itself is made of Suberin, a cross-linked somewhat-rubbery substance consisting of both polyaromatic (such as hydroxycinnamic acids and their derivatives) and polyaliphatic moieties (such as α-Hydroxy Acids and diacids ) with somewhat variable cross-links between them. The variable substance called Phlobaphen also occurs as one of the polyaromatic components of suberin. Cork Oak is the tree used to make cork bottle stoppers. Under the microscope cork is found to have an irregular lattice framework full of holes, which is why cork is so light and springy. Suberin is also the biopolyester found in specialised plant cell walls to be found wherever protection from water or gas exchange is paramount, for it is impervious to both water and gasses. It is also created in plants to repair any tissue damage, for instance leaf abscission or any wounding of the plant. Both Cutin and Cutan are similar random waxy polymers. Cutin covers all aerial surfaces of plants like a cling-film layer to protect them from fungi, bacteria and other pathogens by being a physical barrier. Cutan is rarer in plants but is much more likely to preserve plant material over historical timescales than is cutin. Lignin is another random polymer film produced by plants for the purpose of protection.


Quinic Acid, is a cyclic polyol found in Coffee Beans, Chinchona Bark. It has a perceived acidic and astringent presence in a cup of coffee. Quinic Acid is found Tobacco leaves, Carrot leaves, apples, pears, peaches, plums, vegetables and in the bark of Eucalyptus globulus, a Blue Gum tree. It resembles a sugar compound.


But the most widely reported substance within the fruits is named after the genus in which Strawbery-Tree is placed: Arbutus. That substance is Arbutin (aka Arbutoside), which is a β-D-glycopyranoside of HydroQuinone. Arbutin is also found within the fruits of Bearbery, which although finds itself in the same family (Ericaceae) as Strawberry-Tree, is in a differing Genus (Arctostaphylos).


  Arbutus unedo  ⇐ Global Aspect ⇒ Ericaceae  

Distribution
 family8Heather family8Ericaceae

 BSBI maps
genus8Arbutus
Arbutus
(Strawberry-Tree)

STRAWBERRY-TREE

STRAWBERRY TREE

Arbutus unedo

Heather Family [Ericaceae]