am
2003-11-11 21:28
Gallux,
na drzewo z takimi odzywkami-(bez rewanżu)- na to trzeba zasłuzyc...
Basiu.. dlaczego ten facet (jesli to cos mozna nazywac facetem) nazywa Ciebie swoim podworkiem. Czy o czyms nie wiem?
:)
2003-11-11 21:28
dla mnie nielojalnośc jest zdradą
dobranoc paniom i panom a Basi więcej optymizmu i wiary w samą siebie
to banalne słowa ale innych jakoś nie znam:)
2003-11-11 21:29
Basiu on z 52 latami moze sobie tylko pomarzyc. Chocby nnie wiem jak sie staral nic z tego trwalego nie wyjdzie.
To jest roznica pokolen i dlatego nie ma przyszlosci. Zdarza sie, ze mlode wyrachowane dziewczyny wychodza za maz za duzo starszych od siebie dziadkow z wielkim majatkiem.
Dziadek kest dumny ze stac go na mlodke i ze moze sie z taka pokazac. Czyzby twoj stary byl az tak bogaty?
Szkoda ze moje e-maile do ciebie nie dochodza:(
2003-11-11 21:31
Jeden mo tyle inny mo wiecej...
Of butterflies and plants...
Jeffrey B. Harborne
Why do Monarch butterflies store heart poisons? Why does the omnivorous snail avoid certain plants to feed on? Why does the Cabbage White butterfly feed only on plants that contain certain glycosides in their leaves. The answers to these questions, and many more, are to be found in an understanding of ecological chemistry...
Ecological chemistry covers the origin, function and significance of natural chemicals that mediate interactions within and between organisms. One major strand in the development of this subject was the discovery of insect pheromones, and the recognition that trace amounts (eg 1µg or less) of simple organic molecules could exert profound effects on the mating behaviour of Lepidoptera - ie butterflies and moths - and other insects. Equally important was the discovery that kairomones - volatile chemicals released by plants - attract or repel insects to feed or lay eggs (oviposit) on those plants.
Some history
A driving factor in the origin of ecological chemistry was the increasing need to explain the enormously rich variation in secondary metabolism encountered in plants. Literally thousands of complex alkaloids, terpenoids and phenolics have been recognised as occurring in higher plants. In 1959 biologist Gottfried Fraenkel,1 at the University of Illinois, argued that the raison d'être of these 'secondary metabolites' could not be explained by the idea that they are simply 'waste products' of primary metabolism, accumulating in the plant cell because of the absence of an efficient excretory system. Instead, Fraenkel described these metabolites as 'trigger' substances, which induce or prevent the uptake of nutrients by plant-eating animals (herbivores).
In 1964, Paul Ehrlich and Peter Raven2 were among the first to propose a defined ecological role for plant products as defence agents against feeding insects. They hypothesised that, through the process of co-evolution, insects can detoxify certain defence agents that deter feeding so that, eventually, the same deterrents become feeding attractants. Their theory helps to explain the relatively restricted feeding preferences of many insects, eg Cabbage White butterflies only feed on plants that contain glucosinolates (ie mustard oil glycosides).
Another important event in the history of ecological chemistry was the recognition that Lepidoptera with warning coloration can utilise plant toxins for their own protection. Thus, in 1968 organic chemist Tadeus Reichstein and his colleagues3 at the University of Basle, Switzerland, established that Monarch butterflies isolate and store heart poisons or cardiac glycosides, which are present in their food plants, ie Asclepias sp. At the same time biologist Lincoln P. Brower showed that the cardiac glycosides in this butterfly were emetic (ie vomit-inducing) to blue jays. In this way the Monarch butterflies avoid bird predation.
Since then, scientists have done many experiments to establish the value of secondary metabolites in protecting plants both from insect feeding and animal grazing. To take but one example from the recent literature, there is the case of the butterbur plant and snail grazing. Snails are omnivorous in their feeding behaviour, they feed on an extremely wide variety of plants, especially in the vegetable garden, and yet there are plants they avoid. One of these is the butterbur (Petasites hybridus), a plant that grows in wet places and is related to the commonly found, wild coltsfoot. Two sesquiterpenoids in the leaves of butterbur, petasin (1) and furanopetasin (2), deter the snails completely. The concentrations of these compounds in the leaves are 0.07-0.72 per cent dry wt. In laboratory feeding experiments, concentration levels of 0.05 per cent dry wt are sufficient to cause 100 per cent deterrence.4
The Monarch butterfly...
The most striking evidence that plant chemicals may be protective against their herbivores is the fact that some butterfly species 'borrow' toxins from plants during feeding at the caterpillar stage and then store these toxins at the adult stage in the body, which successfully defend the butterflies from birds and other predators. The best known example of this behaviour is provided by the Monarch butterfly, Danaus plexippus, a North American species but also an occasional visitor to the British Isles, and the milkweed plant Asclepias curassavica, the white latex of which contains toxic cardenolides which are heart poisons.
The Monarch butterfly has a striking coloration with bright orange and black wings. It is an 'aposematic' (warning) insect, since its bright colours warn off an animal predator (a bird or a mouse) from eating it. An international team of chemists - Lincoln Brower in the US, Miriam Rothschild in the UK and Tadeus Reichstein in Switzerland - solved the problem of this remarkable butterfly's excellent defence system.3 The caterpillar, also brightly coloured, feeds exclusively on a milkweed, A. curassavica, or a close relative, and isolates the cardenolides, eg asclepin (3), in the latex from its diet. Sufficient of these chemicals are retained in the adult insect (imago) to make a naive blue Jay sick when it tries to feed on the butterfly. A blue Jay, so trained, then ignores completely a second Monarch butterfly it might meet.
The cardiac glycosides indeed have an emetic effect on an animal grazer, and they protect the milkweed effectively from cattle grazing in the prairies of North America. It is clear, also, that this butterfly has to be especially adapted to ingesting these toxins so that it does not suffer any poisoning itself. This is only part of the story and there are other complexities in this butterfly-plant interaction. For example, the butterfly also borrows other classes of toxins, including the volatile alkaloidal pyrazines and the pyrrolizidine alkaloids, taken in plant nectar by the adult.5
The Marbled White butterfly...
Another fascinating example of ecological chemistry in action is the Marbled White butterfly, Melanargia galathea and its food plants, the perennial sheep's fescue widely found on the British Isles. The distinctive black and cream wing coloration of this butterfly suggests that it is protected from bird predation. It is slow and languid in flight, resting regularly on the fescue's flowers to collect nectar.
Experiments in my laboratory at Reading6 have shown that this butterfly is unusual among insects in isolating flavonoid pigments (glycoflavones and tricin (4) glycosides) from Festuca rubra and F. ovina. The caterpillar transfers the flavonoids to the adult, and these chemicals provide the cream-white colour of the wings against a black melanin-based background. What is even more interesting is that the pattern of flavonoids in the adult is specifically derived from the Festuca plants. Thus the pattern of wild English butterflies differs significantly from those of butterflies raised in the laboratory from caterpillars fed on other common grass species. A study of the chemistry of the Marbled White confirms that the caterpillar normally feeds exclusively on Festuca, ignoring the other common pasture grass species available to it. Since flavonoids are essentially non-toxic, the isolation of these substances from the food plant provides coloration both in the visible region and in the ultraviolet, where flavonoids absorb strongly.
What then is the apparent chemical defence of this butterfly? Recent research by Miriam Rothschild7 and Robert Nash in this country has revealed that the Marbled White butterfly absorbs a second type of chemical from its food plant, and is chemically protected by loline (5), a saturated pyrrolizidine alkaloid. What is especially remarkable here is that alkaloids are not normally synthesised by grasses. In fact, the loline is produced on the Festuca as a result of infection by the common fungal endophyte, Acremonium sp. (ie a fungus that grows within the plant cells). This butterfly is apparently unique in depending on a fungus, via a higher plant, to provide it with its chemical defence.
The Cabbage White butterfly...
The final example, which illustrates the importance of plant chemistry to insect feeding, is the Cabbage White butterfly, Pieris brassicae, and the mustard plant. This is the story of a plant chemical which is synthesised by that plant as a general feeding deterrent, and of specialised insect species overcoming this defence and turning the toxin into a feeding attractant. The toxin then becomes so vital to the insect that it may prefer to starve to death rather than eat plant tissue lacking this stimulant.
The insects that have been most studied are the Cabbage White and the Small White Pieris rapae, but there are a host of insect species that feed specifically on mustard plants. The plant family involved is the Cruciferae, which includes the mustard itself, Sinapis alba, and the cabbage Brassica oleracea. The chemistry of this family is dominated by the presence of mustard oil glycosides, or glucosinolates. Sinigrin (6) is a typical member, which releases an acrid oil, allyl isothiocyanate (7), on enzymic hydrolysis (Scheme 1). Since an insect feeding on mustard or cabbage will release the isothiocyanate during eating, it is not always clear whether it is the sinigrin or the allyl isothiocyanate which is the active component.
Scheme 1. Enzymic hydrolysis of sinigrin
The fact that sinigrin is a positive feeding stimulus to 'cabbage' butterflies has been demonstrated in several experiments. Thus larvae of the cabbage butterfly can generally be persuaded to feed on an artificial diet only if mustard oil (or the glucosinolate) has been added to it. It is possible to take newly hatched larvae and get them to feed on a diet devoid of mustard oil, but even with these insects addition of glucosinolate to the diet immediately increases feeding intake by 20 per cent. The dependency of the larvae on this feeding stimulant is most significantly demonstrated in the case of insects fed from the start on cabbage leaves. When these larvae are transferred to an artificial diet lacking sinigrin, they refuse to eat and, in fact, prefer to die rather than accept food lacking what has become an essential attractant. The importance of sinigrin to Pieris brassicae is evident in other aspects of their life-cycle. The adult female, for example, uses the same substance as an egg-laying stimulant. Indeed, the butterfly can be fooled into laying its eggs on a piece of filter paper if the paper has been previously soaked in a solution of sinigrin.
Table 1. Effect of the glucosinolate sinigrin on a range of plant-feeding insects
• Feeding attractant to cabbage aphid, but high concentrations in the phloem of young plants deter feeding
• Feeding attractant to horse radish flea beetle; leaf flavonoids are also attractants
• Feeding attractant to mustard flea beetle at 2mmol dm-3 but high concentrations in young plants (20mmol dm-3) deter feeding
• Feeding attractant to treacle mustard flea is cancelled by presence of cardenolides in the same leaves
• Feeding attractant to the garlic mustard plant is cancelled for the small white butterfly by cyanoglycosides and glycoflavones present in the leaves
• No feeding attraction to a non-specialist on crucifers, eg the black swallowtail butterfly. In fact a 0.1 per cent dry wt solution is toxic
Some of the effects of glucosinolates on other insects are described in Table 1. Two points are worth mentioning:
• the concentration of glucosinolate in the plant is crucial in determining whether feeding takes place or not;
• it is apparent that the rest of the leaf chemistry of a particular crucifer plant is also important in controlling feeding. Thus, an ovipositing cabbage butterfly female will not lay her eggs on a plant of Erysimum cheiranthoides because of the presence of cardenolides in addition to the glucosinolates. If she did, the eggs would hatch and the young larvae would be poisoned by the dietary cardenolides.
The challenge
While I have illustrated ecological chemistry here with examples from plant-insect interactions, this branch of chemistry also embraces chemical aspects of plant-mammalian, animal-animal, and plant-microbial interactions. It is a burgeoning field in which the organic chemist has to identify and measure vanishingly small amounts of often volatile chemicals that are released into the environment by the plant or animal. Teamwork is essential and the field ecologist has an equally important role. There are also practical applications of ecological chemistry, eg in pest control. Some idea of the range of topics now encompassed by ecological chemistry can be gained from a recent historical review of the first 25 years of ecological chemistry.8
2003-11-11 21:33
Nielojalność- czy dzisiaj ktos jescze pamieta o co chodzi w tym pojęciu?
2003-11-11 21:33
on ma nadzieje byc bogaty jak sad przyzna mu polowe wszystkiego co mamy... Ja mam nadzieje ze mu nie przyzna - przynajmniej ja wole wydac na adwokatow niz jemu dac na panienke. Jest jubilerem - to sama wiesz...
sPORTOWIEC - kochany jestes ze mnie rozsmieszasz. Nie jestem galluxa podworkiem - on tak "poetycznie" w przenosni... wiesz - pokolenie romantykow.
2003-11-11 21:37
Juz sie Basienko tłumaczysz a Galluxa...Sama widzisz- tylko z nim kłopoty. Ale swoja droga powiem Ci szczerze, że ten Gallux to dziwny facet. reaguje czesto jak więzien w celi. Nie czuje takich facetow i staram sie ich omijac wielkim łukiem.
2003-11-11 21:42
gallux jest bardzo charakterystyczny w swym zachowaniu. Unikalny - powiedzialabym... Ale lubie go za to ze jest "inny" w bardzo roznym tego slowa znaczeniu. Jest czesto impulsywny - ale nikt nie jest idealem - prawda? Ale tez czesto gallux ma tyle "serca na dloni" ze niewielu ludzi na to stac. No coz, ludzie sa rozni a od nas zalezy jak ich postrzegamy - prawda?
2003-11-11 21:43
ja wysle ci pocztowke moze dojdzie otworz ja.
Pisalas, ze on jest jubilerem, ale on jest skorpionem i niech sie pilnuje, zeby swojej polowy materii nie stracil bo jeszcze jest za mlody,
zeby jakas laska mogla czekac kiedy on w kalendarz kopnie.
2003-11-11 21:43
Basiu
ja ci radze, pokaż klase
dogadaj sie z nim, zawrzyj kompromis podzielcie majatek między siebie
jak dopuścicie adwokatów to oboje przegracie
oni was puszczą z torbami
na spokojnie bez emocji PO KUPIECKU wystaw rachunek i wolny niech ma te 19-latke i młodsze, lepiej późno niż wcale:)
mądry Polak po szkodzie
jak i po rozwodzie
dobranoc
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