There are lots of interesting examples of how plants communicate with insects. For instance, in self-defense against insects eating its leaves, a plant emits a volatile chemical that signals other insects, who are predators of those insects eating the plant. A byproduct of such insect communication may allow plants to signal danger to other extremely close, downwind plants. Professor of Entomology, Richard Karban and other researchers from the University of California showed that a cut sagebrush “told” nearby, downwind wild tobacco plants about its injury, and the tobacco plants apparently responded to protect themselves from damage. Over three seasons, researchers clipped leaves of sagebrush plants to mimic insects eating their leaves. The cut sagebrush released volatile chemicals (methyl jasmonate), which the wind carried to nearby downwind plants. The tobacco plants apparently sensed the chemicals-at least the tobacco plants increased production of a defensive agent-that caused their leaves to taste bad to insects. These downwind tobacco plants experienced less than half the leaf damage from grasshoppers and cutworms than control plants (Anon.). In one case study an acacia tree responded to browsing, or being beaten with a stick, by increasing the levels of tannin in its leaves within minutes. Amazingly, the tannin levels then rise in neighboring trees, and, due to its bitter taste, repel the browsers before they can do any further damage (Jacob 2001; Anon.).

What’s more is that plants can also talk to mammals. A study done by Professor Steven Johnson and his research team from the University of KwaZulu-Natal, South Africa, demonstrated how ground-dwelling mammal pollinators are attracted by a rare parasitic plant’s unique “perfume.” This specific floral aroma is comprised of over 30 compounds, especially ketones, fatty-acid derivatives, mono- and sesquiterpenoids. The three most abundant scent chemicals were 1-hexen-3-one, 3-hexanone, and ethyl butyrate. When the impact of these chemicals was tested on mice, it turned out that mice, like humans, find 3-hexanone to have a pleasant smell. The molecule is routinely used in artificial flavoring to produce a sweet fruity grape-like flavor. In addition, 3-hexanone has also been found in some bat-pollinated flowers, so it may be a general mammal attractant. Remarkably, scent cues are particularly important to plants pollinated by small ground-dwelling mammals because these animals are usually around at night when visual cues are less effective (Johnson et al. 2011; Anon.).

In addition to pests, plants have to deal with numerous microbial pathogens such as bacteria, fungi and oomycetes, and viruses in the natural environment. A proper response to pathogens can lead to resistance mechanisms that enable plants to survive. Plants can recognize potential pathogens by detecting pathogen-associated molecular patterns (PAMPs). This recognition activates a defense mechanism. A well-organized communication between the pathogen-invaded plant tissues and non-invaded ones is essential for the timely manifestation of defense mechanisms that limit the systemic spread of pathogens (Shah 2009). Salicylic acid, an important mobile signal, is transported from infected tissue to the rest of the plant body. It activates the systemic acquired resistance, which is a “whole-plant” resistance response that occurs following an earlier localized exposure to a pathogen. Plants not only communicate within themselves about a microbial invasion, they also talk to one another. For example, Tobacco plants warn each other against tobacco mosaic virus attack by releasing methyl salicylate, which is then converted to the protective salicylic acid in uninfected plants (Jacob 2001).

In contrast to harmful pathogenic interactions, there are also symbiotic, advantageous interactions between some microorganisms and plants. Establishment of such a beneficial symbiosis (which literally means “living together” in Greek) is complex. For successful infections, a molecular dialogue between partners is essential (Vadassery and Oelmüller 2009). Among these kinds of interactions, legume-Rhizobium symbiosis is of particular importance in agriculture, because by forming the symbiosis, atmospheric nitrogen can be used to sustain the growth of legume crops, such as soybean, pea, and bean, which occupy 12% to 15% of the land that can be used for growing crops throughout the world (Sugiyama, Shitan, and Yazaki 2007). Rhizobia are soil bacteria that fix nitrogen (diazotrophs) after becoming established inside root nodules of legumes such as alfalfa, clover, peas, beans, lentils, lupins, mesquite, carob, soy, and peanut.

Rhizobia require a plant host, since they cannot independently fix nitrogen (Anon.). Plant roots secrete signaling molecules (e.g. flavonoids) to attract Rhizobia. When Rhizobia sense these chemicals, they colonize around root tissues of the host legume plant. So, the rhizobial infection in legumes is an invasion by invitation (Murray 2011). The attached rhizobia secrete Nod factors, which are perceived by the plant. This initiates a series of events that leads to the formation of nodule, where Rhizobia fix nitrogen. Thus, Rhizobia make legume independent of soil nitrogen and the legume supplies nutrients to the bacteria. In addition, the legume plant supplies one critical component of nitrogenase, which is the key enzyme for fixing nitrogen. It all happens because the plant can talk to the bacteria.

The plant has many interests in being colonized by mycorrhizal fungi. Apart from providing nutrients such as phosphorus and nitrogen, the fungi protect plants from diseases, parasites, and other stresses. Plants even grow as much as 40% more when colonized. In laboratory experiments, carrots that were colonized grew 20 times more than the carrots that were not! In fact, they are such close “friends” that the fungus cannot live without a plant, and between 80-90% of all plants on earth are somehow associated with mycorrhizal fungi. The origin of this incredible friendship is communication (Montréal 2012).

As a result, plants can talk to microorganisms, pests, and mammals, but do they communicate with people? Are they intelligent creatures who can communicate with us? In 1848, Dr. Gustav Theodor Fechner, a German professor, suggested that plants are capable of emotions and that one could promote healthy growth with talk, attention, and affection. An Indian scientist, Sir Jagdish Chandra Bose, conducted experiments on plants in 1900. Bose found that plants grew more quickly amidst pleasant music and more slowly amidst loud noise or harsh sounds (Sir Patrick Geddes and Geddes 1920).

Moreover, according to Royal Horticultural Society, talking to plants helps them grow, especially if the one talking to the plant is a woman. Even though there are lots of divisive experiments done with plants to understand if they can talk to human beings, there is no serious finding about this subject yet. Even if, plant biologists do not currently know how to talk to plants, they strive to comprehend how plants communicate with other organisms in order to use this new and exciting language for improving the resistance of plants against pests or pathogens. Instead of using chemical pesticides, genetically engineered plant defense and communication pathways in crops are a preferred avenue.

Communication of plants with other organisms is such a complex problem. Plants can have a network with so many different creatures. They pass on information to each other or to other organisms that speak other languages. How did they obtain these amazing communication skills? Even the most advanced creatures, human beings, experience problems in communication, how can plants have robust communication systems in a heterogeneous environment?

The next time you hear a strange rustling among your garden plants, maintain distance. They might be having an argument. Plants also talk and they respond to attacks like we do. So, be careful and do not hurt plants as they might even curse or scream to you (Anon.).

Safiye Arslan is a research fellow in the area of molecular biology in Nevada.

References

• Adler, Frederick R. 2011. Plant signalling: the opportunities and dangers of chemical communication. Biology Letters. http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=3061173tool=pmcentrez&rendertype=abstract.
• Anon. Do plants talk? What are the chances it’s a boy? – USATODAY.com. http://www.usatoday.com/tech/columnist/aprilholladay/2006-07-24-plant-talk-baby-boys_x.htm.
• Anon. jacobson’s organ and the remarkable nature of smell. http://books.google.com/books/about/Jacobson_s_Organ_and_the_Remarkable_Natu.html?id=liKKQgAACAAJ.
• Anon. BBC – Earth News – “Perfumed” parasitic plant lures in pollinating mammals. http://news.bbc.co.uk/earth/hi/earth_news/newsid_9376000/9376474.stm.
• Anon. What is Rhizobia. http://www.bionewsonline.com/y/what_is_rhizobia.htm.
• Anon. Biotechnology: Plantlinguistic: – “Plants Communicate With Each Other.” http://bioinformations4all.blogspot.com/2009/08/plantlinguistic-plants-communicate-with.html.
• Jacob, Tim. 2001. “The science and myths of smell.” EMBO Reports 2 (10): 880. http://www.nature.com/embor/journal/v2/n10/full/embor301.html.
• Johnson, Steven D, Priscilla M Burgoyne, Lawrence D Harder, Stefan Dötterl, and Proc R Soc. 2011. “Mammal pollinators lured by the scent of a parasitic plant Subject collections Mammal pollinators lured by the scent of a parasitic plant.” Society 278 (January): 2303-10. doi:10.1098/rspb.2010.2175. http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=3119003&tool=pmcentrez&rendertype=abstract.
• Montréal, Jardin botanique de. 2012. “Chatting with a plant’s best friend – Science +” (June 3). http://www.aucoeurdelarbre.ca/en/thematics-texts/thematics-texts-details.php?id=8.
• Murray, Jeremy D. 2011. “Invasion by invitation: rhizobial infection in legumes.” Molecular plantmicrobe interactions MPMI 24 (6): 631-639. http://www.ncbi.nlm.nih.gov/pubmed/21542766.
• Shah, Jyoti. 2009. “Plants under attack: systemic signals in defence.” Current Opinion in Plant Biology 12 (4): 459-464. http://www.ncbi.nlm.nih.gov/pubmed/19608451.
• Sir Patrick Geddes, and Sir Patrick Geddes. 1920. The life and work of Sir Jagadis C. Bose. Longmans, Green. http://books.google.com/books?id=EPtCAAAAIAAJ&pg=PA97&q=”continuous”#v=twopage.
• Sugiyama, Akifumi, Nobukazu Shitan, and Kazufumi Yazaki. 2007. “Involvement of a soybean ATP-binding cassette-type transporter in the secretion of genistein, a signal flavonoid in legume-Rhizobium symbiosis.” Plant physiology 144 (4) (August): 2000-8. doi:10.1104/pp.107.096727. http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=1949875&tool=pmcentrez&rendertype=abstract.
• Vadassery, Jyothilakshmi, and Ralf Oelmüller. 2009. “Calcium signaling in pathogenic and beneficial plant microbe interactions: what can we learn from the interaction between Piriformospora indica and Arabidopsis thaliana.” Plant signaling & behavior 4 (11) (November): 1024-7. http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=2819509&tool=pmcentrez&rendertype=abstract.

It is estimated that 80 to 90 percent of all cancer cases are related to environmental and lifestyle influences (1). Many cancer research centers estimate that 80 to 90 percent of human cancers are preventable. Beside chemicals and infections (viral and parasitic), extrinsic factors include diet among a variety of other factors wholly or partly determined by personal behaviour. Though genetic factors and age affect cancer onset rates, the conclusion holds that many human cancers are avoidable (2). A great number of these are related to tobacco smoking and chewing, alcohol consumption, homosexuality, promiscuity and excessive exposure to solar radiation as in sunbathing, all practices disapproved in traditionally religious societies.

Dr John Hill, a London physician, reported an increase of lip cancer in pipe smokers as long ago as 1761. Sir Percival Pott reported cancer of the scrotum in chimney sweeps in 1777, which he attributed correctly to lodgement of soot in the rugose scrotal skin. This type of cancer was virtually eliminated by simple personal hygiene (3). Later, many chemicals were proved to be carcinogenic and hence many cancers became avoidable by taking more care when dealing with them. Ionizing radiation is still an important hazard, preventable by taking better care.

Tobacco and Cancers

In many countries cancer is the second most important cause of death. In the USA and many developed countries, it accounts for 20 percent of all deaths (1,2). An estimated 6 million new cases of cancer occur annually worldwide, of which about a million are caused by tobacco smoking and chewing (4). The death toll due to malignant disease in the USA amounts to 400-450,000 annually of which 100,000 are due to lung cancer, 85 to 90 percent of those due to cigarette smoking (1,2). Indeed, tobacco (smoked, chewed or sniffed) is the most important single factor in cancer causation generally, responsible for 30- 40 percent of all cancers (5). No other single agent has been examined in more detail, nor more firmly established as a causal agent, than cigarette smoking (6). Let us look at some of the facts.

The risk of cigarette smokers developing lung cancer increases with the number of cigarettes smoked the duration of smoking, the time of onset and the type of smoking. Approximately one-sixth of those who smoke two packs of cigarettes per day will eventually develop lung cancer. The risk to hose who smoke 40 cigarettes per day are 25 times more that to non-smokers (6-8). Cigarette smoking causes all ol the major types of lung cancer including squamous cell carcinoma, adeno carcinoma, oat cell and large cell carcinoma (6). Cancer of the lung was a rare form of cancer at the beginning of this century, even in developed countries. As smoking increased dramatically after World War I among men, and among women after World War II, the incidence of cancer of the lung showed incessant increase until the seventies, after which it began to decline among men and a decade later among women. Nevertheless, cancer of the lung is still the first killing cancer among men and women in many developed and developing countries (7,9,13). In Hong Kong, the rates for women are now the highest in the world (13). Lung cancer rates in Chinese men (e.g. 50.2 per 100.000 in Shanghai) are higher than in many North American and European populations (13). It is the leading cause of cancer mortality among males in Bulgaria. Cuba, Czechoslovakia, Egypt, Greece, Hong Kong. Hungary, Israel, the Philippines, Poland, Romania, Singapore, Thailand, Uruguay and Zimbabwe. The risk is particularly high among cigarette smokers, and a clear cut dose-response relationship has been confirmed. The risk is greater among those who started smoking at a young age and those who smoke high tar cigarettes (2,14-16).

Laryngeal cancer is the second cancer caused by cigarette smoking, but the total number of cases is smaller than lung cancer and the survival is much better (6). Cigarette smokers are five times more likely to develop cancer of the oral cavity and the oesophagus than non-smokers (&-8). There is synergism between alcohol and cigarette smoking in causing cancer of the larynx oesophagus and oral cavity(6-8.14-16,22).

Cigarette smoking is also an important contributing factor in cancers of the bladder, kidney and pancreas. Association between gastric cancer and smoking has also been noted (23-26). Cigarette smoking has even been implicated in cancers affecting the breasts, kidneys, liver, cervix, uteri and many other organs (27-29). It has also been implicated in childhood cancer as a result of prenatal exposure to parental smoking (30). Passive smoking was implicated in causing many cases of cancer (31-33).

Non-smoked Tobacco

Long term use of chewing tobacco or snuff has been linked to cancer of the oral cavity, cheek, gums and oropharynx (6). Oral cancer is one of the ten most common cancers in the world. In Bangladesh, India, Pakistan and Sri Lanka, it is the most common malignant disease and accounts for a third of all cancers. More than 100,000 new cases occur annually in South and South East Asia (13). The commonest cause for oral cancer is tobacco chewing, usually in the form of betel quid which consists of betel vine leaf (piper betel), areca nut, lime and tobacco (13,34). Tobacco chewing is also widespread in parts of Yemen, Sudan and Southern Province of Saudi Arabia: the so called ‘shamma’ is a tobacco plus lime and ash mix, implicated in many cases of oral cancer in these areas (35,36).

Tobacco was propagated in developed countries by tobacco companies after the decline of cigarette smoking there. The 39th World Health Assembly in 1986 adopted Resolution WHA39 which declared that ‘the use of tobacco in all its forms is incompatible with the attainment of health for alt by the year 2000’ (37). The study group concluded that the use of smokeless tobacco caused cancers in humans, the evidence of causality being strongest for cancers of the oral cavity. It also increased the risk of cancers of the nasal cavity, pharynx, larynx, oesophagus, pancreas and urinary tract. Laboratory studies clearly supported the observations that smokeless tobacco caused a number of precancerous oral lesions (37).

Carcinogens in Tobacco Smoke

Tobacco smoke is an aerosol consisting of about 2000 different substances, 50 of which are already proven to be human carcinogens e.g. Benza pyrines, Benza anthracene, Benzo floaranthene, Benzene and other Benzyl derivatives, cadmium, chrysene, methylchryscne, methyl fiouranthene and nitroso compounds (38,39).

Cigarette smoke also contains significant amounts of radioactive substances e.g. thorium Th228, polonium-210 and radium-Rd226. These compounds lodge in the lungs where they constantly irradiate the nearby cells and hence facilitate malignant change (38). Even the urine of cigarette smokers contains mutagenic substances for bacteria, and substances that cause changes in the chromosomes of human cells in tissue culture.

Sidestream smoke which is inhaled by non-smokers contains fifty fold greater concentration of nitrosamines than mainstream smoke. In one hour of breathing in a smoke filled room, a non-smoker may inhale an amount of nitrosamines equivalent to the amount inhaled after having smoked 15 filter cigarettes (38).

Cessation of Smoking

The risk after cessation of smoking decreases dramatically. Light smokers approximate the risk of nonsmokers after 10 to 15 years of cessation of smoking, while heavy smokers have a residual two to three fold increase after cessation (2,6). The mechanism of lung carcinogenesis and smoking cessation has been extensively studied (40).

Women and Smoking

As women started smoking long after men, there is a time lag in the incidence of lung cancer. The incidence of lung cancer has already fallen for men in most developed countries while it was still increasing for women early in the eighties. In 1984, 32 percent of the women smoked in Britain compared with 36 percent of men. In 1961, the figures had been 60 percent of men, and 40 percent of women. Whereas in 1950 the average woman smoker smoked half as many cigarettes as the average male smoker, in the eighties the corresponding figures were 14 and 16 cigarettes (41).

During the second decade of the anti-smoking campaign in Britain, smoking started to fall among women too, slowly at first, but with accelerating momentum (42). Similar trends are found in all developed countries, In some countries e.g. Australia, smoking among young and middle aged women was rising in the early eighties (5,43A4). The proportion of male smokers was falling in 19 out of 22 developed countries, and for women rising or stable in II countries (42-44). In Austria, Germany, Italy, Japan, U.S.S.R., smoking among women was still rising in the early eighties(42).

We may note that lung cancer has already surpassed breast cancer in the number of fatalities it causes. Non-smoking wives of smoking husbands (passive smokers) and non-smoking women working in smoking environments are also afflicted with lung cancer(6,31-33.37).

Trends in Developed and Developing Countries

Anti-smoking campaigns have been launched in the developed countries in the last three decades with tremendous achievements. In Britain, 60 percent of men were smokers in 1961 (the year before the first report of the Royal College of Physicians about smoking was published). By 1971 this figure had dropped to 47 percent, by 1984 to 36 percent, and by 1992 less than 25 percent of the adult males are smoking. As already noted, a similar trend among women smokers was apparent with a ten-year lag (42-45). The decline in cigarette consumption in other European countries and the USA has been comparable. By the mid-eighties sales had plummeted by an impressive 2$ percent with a 5-10 percent annual decline (42-44).

How have the tobacco companies been selling the 10 billion cigarettes they produce daily? By promoting sales in the poor Third World, already suffering from serious health hazards. Consumption of tobacco in Third World has seen a horrendous increase. The World Health Organization (WHO) has reported that tobacco related diseases are on the rise in developing countries.

During the last three decades: in Senegal the percentage of men who smoke in urban areas has reached an unprecedented 80 percent in Bangladesh 70 percent; in Lagos 72 percent of the Faculty of Medicine male students were smoking (46). Statistics from the Chamber of Commerce of Saudi Arabia show an unbelievable increase in tobacco imports: over 4,5 million kgs in 1972: over 27 million kgs in 1977; nearly 36 million kgs in 1981; 42 million kgs in 1984 – an increase of 900 percent (47-48). It is no surprise to find that lung cancer in Saudi Arabia has increased dramatically – from the twelfth most common cancer in a 1950-61 study (49) to the third most common cancer in a 1979-84 study (50). It is expected to be the leading cancer in the nineties us the effects of smoking are unfolding.

The tobacco companies’ methods are unscrupulous as well as aggressive, with bribery of government officials to permit promotion not unusual. In 1982, the head of the Malaysian parliament retired and went to work as a chairman of Rothman’s, Malaysia’s largest cigarette manufacturer (48-51). Ethiopia imported 200 million expensive British cigarettes in 1984 when a large portion of its population were starving to death (52). In Bangladesh, smoking of five cigarettes daily robs the family of a quarter of its food supply, which results in an estimated 18.000 deaths among children annually (53). Unfortunately, the World Bank and Western Governments are co-operating with the seven giant tobacco companies (three American, three British and one French). The World Bank has given Pakistan 60 million dollars in loans to raise tobacco and the US Food for Peace Programs have spent 2 billion dollars in loans to developing countries for the purchase of U.S. tobacco and to establish joint-venture tobacco projects and factories (48-51). Tobacco needs to be cured with heat, obtained by burning wood. This results in deforesting 7 million acres annually with the obvious detrimental impacts on the local ecology, Heavy use (without protective measures) of carcinogenic pesticides on tobacco plantations has also resulted in many fatalities.

Neither tobacco promotion nor high tar content are restricted in many third world countries. Cigarettes smoked in China. India. Pakistan. Sri Lanka the Philippines etc. contain 21-33mg tar and 2-3mg nicotine: while in tile developed countries of U.S.A., Canada, Western Europe, the maximum legally permitted levels are 15 mg tar and 1 mg nicotine (13,46,48).

China consumes one third of the world’s production of cigarettes, while the other developing countries consume another third (48,54). The Eastern and Western block combined consume the remaining third.

The WHO emphasizes the need for a ban on tobacco promotion which should be comprehensive, fully implemented, well publicized, given major priority by governments and health authorities, and sustained on a long term basis (13).

Islamic Law and Tobacco

Muslim muftis and grand ‘ulama’ proscribed smoking tobacco soon after it was introduced to Turkey around 1000H (1573). Sultan Murad of the Ottoman Caliphate made it a capital offence in 1663. The former Grand Mufti of Saudi Arabia, Sheikh Mohammed bin Ibrahim (55) included in his fatwa the names (If many grand ‘ulama’ and muftis who had proscribed tobacco use since its first appearance in Turkey, Morocco, Egypt, Syria, and Yemen (56). All the religious authorities in Saudi Arabia, including of course the present Grand Mufti, Sheikh Abdul Aziz bin Baz, prohibited tobacco use, its promotion, sale, cultivation or dealing with it in any way other than destroying it.

Recently the 1st International Islamic Conference of ulama’ (On Drugs, Narcotics and Liquors held in Madina, March 22-25, 1982, under the auspices of Crown Prince Abdullah bin Abdul Aziz passed a resolution prohibiting the use of tobacco in any of its forms, its cultivation, manufacture, trading in. selling or promoting it in any way (57). The WHO Eastern Mediterranean office published a book in 1988 under the title Al-Hukm al-Shar’i fi at-Tadkhin (Islamic legal ruling on smoking) which involved the decision of the ten leading ‘ulama’ of Egypt, including Sheikh Al-Azhar, who explicitly considered tobacco use as haram (58).

The grounds for these judgments were:

1. Smoking is detrimental to health. The Qur’an states clearly Don’t kill yourselves (4.29) and Make not your own hands contribute to your destruction (2.195). Islamic teachings generally, as well as hundreds of sayings of the Prophet, upon him be peace, encourage Muslims to preserve good health and abstain from things injurious to health.
2. Tobacco use wastes huge sums of money. Saudi Arabia spends annually more than one billion riyals on tobacco imports (59). Some poor Muslim countries spend more money on smoking and other tobacco use than on health promotion or education. The Qur’an deplores such waste: Squander not your wealth senselessly. Squanderers are indeed the like of Satans (17.26, 27).
3. Smoking is had and impure, khabath. The Qur’an declares that the Prophet, upon him be peace, forbids all that is bad and impure and allows all that is good and clean (7.157). Smoking is bad and impure, as it Causes environmental pollution and is unpleasant, even seriously harmful, to those who do not smoke, injuring others is completely prohibited in Islam and considered one of the worst sins a believer can commit.

There is a great need to inform Muslim communities about the legal opinions on tobacco use and the rationale for them. The Muslim governments should stand firmly against the pressures exerted upon them by the tobacco companies and their powerful Western backers. If Muslim countries and peoples adhere to the traditional religious lifestyles. They will succeed in avoiding the perils and tragic losses of life and wealth caused by tobacco consumption.