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Showing posts with label Solanaceae. Show all posts
Showing posts with label Solanaceae. Show all posts

Thursday, December 29, 2011

Solanum lycopersicum, Tomato, Solanaceae


My mother always told us not to play with our food when we were kids but when you're a grown-up botanist you just can't help yourself: it's so interesting. I doubt whether zoologists get quite so much pleasure from this activity because animal food is usually dismembered and cooked to oblivion, whereas a lot of the plant food that we eat is more of less intact and open to easy investigation.

This slice of tomato, Solanum lycopersicum, eventually destined to be part of my BLT, shows the essential characteristics of the fruit, which is botanically a berry - defined as a fleshy fruit derived from a single ovary. In the tomato's case it's a multi-seeded berry, with each of the numerous individual seeds attached to the central placenta via its own vascular supply. You can see in this section that the fleshy fruit wall - the pericarp - is divided into distinct layers: the outer exocarp (with more concentrated  red pigment); the mesocarp; and the endocarp which is partly juicy and fills the fruit chambers (loculi) that surround the seed. 



It has all evolved to attract a hungry animal and those seeds in the fruit loculus are perfectly capable of passing through the mammalian gut unharmed. That's why feral tomato plants are often a prominent feature of sewage farms. Seeds of the distinctive yellow fruits of the Galapagos tomato, Solanum cheesmaniae, endemic to those islands, are eaten by Galapagos giant tortoises that disperse the seeds (slowly and not very far away) in their droppings. 
























Tomatoes are said to have been introduced into Europe by the Spanish conquistadors, who found that they were already widely cultivated by Mesoamerican civilisations when they arrived in the New World. For centuries tomatoes were viewed by Europeans with suspicion and considered to be poisonous. Somehow the idea that they were aphrodisiacs arose, first in Italy then in France and finally in England and they became known in all three languages as 'love apples'. The term persisted for a long time and in my copy of Everyman His Own Gardener:The Complete Gardener, written by Thomas Mawe and John Abercrombie and published in 1855 - and which you can download here - they are still referred to both as 'love apples' and tomatoes, although by that time their tasty flavour and nutritious qualities were recognised.


Modern cultivated tomatoes tend to be reliably self-pollinated, with their stigma hidden inside a ring of stamens that shed pollen directly onto its surface, but in wild species the stigma protrudes well beyond the end of the stamens and requires an insect to transfer pollen to it. This is the flower of a cultivated tomato, with the anthers just beginning to shed pollen onto the stigma hidden within.


Part of the pleasure associated with eating a tomato comes from the aroma, which is always far inferior in supermarket chiller-cabinet fruit to the sensory qualities of a warm, ripe tomato picked directly from a plant on a summer's afternoon. That alone makes them worth all the effort needed to grow them, even though it's more expensive to do so. I like the smell of the plants as well when you brush against them in the greenhouse and much of that emanates from the surface hairs, or trichomes, which cover most of the plant. 


There are two kinds of trichomes on tomatoes - long, simple hairs and short glandular hairs whose heads of swollen cells are filled with aromatic compounds.

























You can see both here, on a flower pedicel, with the very short glistening glandular hairs covering it's surface.


Here, at higher magnification, you can see just how densely packed they are. Some tomato genotypes have glandular trichomes that contain particularly high concentrations of insect-repellent volatiles, and there's now a lot of interest in transferring this characteristics to cultivated tomatoes, to reduce the need for growers to use chemical pesticides to tackle aphids, red spider and white fly, which can blight the life of an avid tomato grower.

Monday, December 6, 2010

Chinese lanterns,Physalis alkekengi var.franchettii

My grandmother in Sussex used to grow Chinese lanterns Physalis alkekengi var. franchettii to perfection, but I've always struggled to grow them up here in North-East England, not least because the slugs and snails zero in on them almost as soon as new shoots appear in spring. Looking at the natural distribution of the plant - southern Europe and eastwards across drier parts of Asia, it's not surprising that I haven't been able to grow these well. Gran's garden was mostly flint and chalk and she grew them in a sun-drenched spot in gravel at the base of a south-facing bay window, which provided a fair approximation of the Mediterranean climate and soils that this plant enjoys.

The orange papery 'lantern' is formed from the sepals (collectively the calyx) of the flower that inflates once it has been pollinated, enclosing the....































......shiny red berry within. The dried plant makes a colourful winter decoration but if you leave some outdoors the softer parts of that inflated calyx rot away surprisingly quickly, so that by Christmas you have ....
... only the skeleton of veins left which - with a light spray of gold laquer - makes a delightfully intricate Christmas tree decoration.

There seems to be some taxonomic uncertainty surrounding this plant, which is sometimes known simply as P. franchettii. According to the late Graham Stuart Thomas - a gardener who really knew his perennials - P. franchettii has more pointed lanterns - like those in the first photo above - compared with the rounder P.alkekengi, in the skeletonised example above but, since he also mentions that they hybridise, it's reasonable to conclude that they are merely varieties of the same species.

Friday, July 16, 2010

Henbane Hyoscyamus niger





















Henbane Hyoscyamus niger is a poisonous member of the potato family and has a long history of use by murderers. Its gruesome history, sombre colours and veined petals give it an aura of menace. It's reputed (controversially) to be the poison used by Hamlet's uncle to poison the prince's father, by pouring it in his ear, in Shakespeare's tragedy Hamlet.

Sleeping within mine orchard,
My custom always in the afternoon,
Upon my secure hour thy uncle stole,
With juice of cursed hebona [henbane] in a vial,
And in the porches of mine ears did pour
The leperous distilment; whose effect
Holds such as enmity with blood of man
That swift as quicksilver it courses through
The natural gates and alleys of the body,
And with a sudden vigour it doth posset
And curd, like eager droppings into milk,
The thin and wholesome blood: so dit it mine:
And a most instant tetter bark’d about,
Most lazar-like, with vile and loathsome crust,
All my smooth body.


More recently Hawley Harvey Crippen is reputed to have used it to kill his wife Cora in a notorious case in 1910, when the new-fangled wireless telegraph was used to aid the interception of the fugitive as he fled to Canada.


Like so many plant poisons, the toxic alkaloids found in henbane have medicinal applications and were once used as a hazardous anaesthetic by dentists. The herbalist John Gerard left a graphic account of their use in his herbal of 1597.

“Henbane", he wrote, " causeth drowsinesse, and mitigateth all kinde of paine… ………the leaves, seed, and juice taken inwardly cause an unquiet sleep like unto the sleep of drunkennesse, which continueth long, and is deadly to the party.
The seed is used by Mountibank tooth-drawers which run about the country, to cause worms to come forth of the teeth, by burning it in a chafing dish of coles, the party holding his mouth over the fume thereof: but some crafty companions to gain money convey small lute-strings into the water, persuading the patient, that those small creepers came out of his mouth or other parts which he intended to ease.”

In 2008 celebrity chef Anthony Worrall Thompson confused the poisonous henbane for the edible weed fat hen and published a recipe for its use in salads – a lurid example of the dangers of only knowing common colloquial names for plants rather than identifying them by their scientific names. No one is known to have suffered illness from the chef’s error, perhaps because henbane is not a common wild plant, and the chef didn’t seem to be too perturbed by his mistake. "I was thinking of a wild plant with a similar name, not this herb. It's a bit embarrassing, but there have been no reports of any casualties. Please do pass on my apologies", was his comment.

























Franz Eugen Köhler, Köhler's Medizinal-Pflanzen 1897

Image Source: http://upload.wikimedia.org/wikipedia/commons/6/66/Koeh-073.jpg

Saturday, May 8, 2010

Scopolia carniolica


This sinister plant, Scopolia carniolica, has been lurking in the undergrowth in my garden for several years, slowly spreading via underground stems. The dried-blood coloured flowers, which look as though their tubular corolla has been snipped neatly across with scissors, are not particular notable but it’s the chemical constituents in the plant that are interesting. Scopolia, like many other members of the potato family, is notorious for possessing a wide range of highly poisonous alkaloids. In terms of toxicity, this plant is almost in the same league as deadly nightshade but one particular alkaloid, scopolamine, has given it notoriety. Used in minute doses this compound has been used to treat travel sickness, usually administered in patches that allow it to be slowly absorbed through the skin. At higher doses it’s lethal, but at some point before that delirium and hallucinations set in. Legend has it that witches made a magical ointment from the plant that produced hallucinations of flying when they smeared it on their skin, presumably just before mounting their broomsticks. More recently scopolamine has been tested as a ‘truth drug’ and has often features in spy thrillers..... you know the scenario.....”Ah, so, Mr. Bond, we meet again ..... and this time there will be no secrets .....you’ll tell us everything.... now, you’ll just feel a small prick.... etc. etc.”

Tuesday, April 6, 2010

Angel's Trumpet Brugmansia x candida

The nocturnal scent of Angel's Trumpet is remarkable, suddenly switching on at dusk and filling a conservatory with a fragrance that can be almost overpowering. I have read a story - probably apocryphal, but never mind - that in the plant's native South America mothers wheel their crying infants in prams under these plants because the fragrance is soporific and quickly pacifies them. This particular species is a sterile hybrid and can only be propagated from cuttings. I bought the original plant for £2.50 from Egglestone Hall gardens about twelve years ago and the one in the photo is a 6th. generation clonal descendant. Taking a  cutting every other year and providing a frequent high nitrogen feed produces a 2 metre-tall plant within two years that soon becomes too big for its pot and our small conservatory and must be propagated from cuttings again. Tonight the current incarnation has ten nine inch-long blooms open and the scent pervades the whole house .... it's been flowering since November and there are still plenty of buds to open. That original £2.50 was the bargain of the century.
Seen from below, the buds have this intriguing spiral twist just before they open fully.
Brugmansia, like many members of the potato family (Solanaceae) contains extremely toxic alkaloids which, in appropriate doses, have important medicinal uses .