Sustainable agriculture and phytochemistry

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Recent Res. Deve!. in Pbytocbem., 2 (1998)

Sustainable agriculture and phytochemistry Massimo Maffei Dept. Plant Biology. University of Turin, ViaJe P.A. Mattioli, 25 1-10125 Turin, Italy; E-mail : [email protected]

ABSTRACT Sustainable agriculture is a practice in vol ving the management of resources for agriculture to satisfy the human needs, without compromising the ability of future generations to meet their own needs. The application of sustainable agricultural and technological methods for a sustainable production of phytochemicals is discus sed. INTRODUCTION Sustainable agriculture is a global issue. It is a practice involving the management of resources for agriculture to satisfy hu man needs, without compromising the ability of future generations to meet their own needs. But what is the meaning of sustainabi lity with regard to natural resources? What is to be sustained, for how long and for whom? According to some authors (l), it is more convenient to consider the concept of unsustainability, which is the complementary side of sustainability. However, in this way only the limits of uncertainty are seen and, even though it has to be considered as well, this does not contribute to the development of models and methods able to provide a system that

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sustains itself without degrading the land, the environment and people. Sustainable agricultural systems reduce the costs of purchased inputs and provide a sustained level of production and profit from far rrung. Among the various objectives of sustai nable agriculture the major one is the re duction of inputs into crop production moving world agriculture closer to the goals of profitability, competitiveness and environmental stewardship (2). To obtain such a goal we should: (iYprotect plants from disease and pests; (ii) consider the yield limitations of the agrosystem; (iii) use forage legumes to improve the soil; (iv) use pathogen-free seeds and pest-re sistant crops; (v) maximize benefits of be neficial organisms; (vi) reduce the use of pesticides and inorganic fertilizers; (vii) preserve the organic matter of the soil; (viii) make the most efficient use of non renewable resources; (ix) utilize renewa ble energy sources such as biological, geothermal, hydroelectric, solar, or wind; and (x) conserve all resources and mini mize waste and environmental damage. All around the world, the cultivation and the production of phytochemicals is limited by agricultural and environmental factors, the presence of specific pathogens and by differences in comparative costs. In developed countries, the continuous

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struggle to try to solve these problems led to the development of high-input agro-in dustrial methods with a considerable use of fossil fuel-derived energy, inorganic fertilizers and pesticides. These agricultu ral methods, which were the fundamentals for the so called "green revolution", need now to be improved to maintain a high yield crop production while protecting the environment and human health (3). In ge neral, the use of inputs eventually leads to increased costs of cultivation and phyto chemicals extraction, thus leading to in creased cost/quality ratios . All these prac tices cause alteration of the ecosystem and the increase of harvestable biomass costs to both humans and the environment (4) . The situation is even more critical in developing countries , where the cost/quality ratio is maintained low at the expenses of human work r.nd health; moreover, the use of organic 1uel relies mainly on deforestation . In underdeveloped countries, cultivation of plants that produce phytochernicals is non affordable, the only plants being harvested from the wild, with the known risk of endangering the preservation and the biodiversity of natural resources. The challenge for the 21st century bur dens again on developed country's shoul ders, for they need to reduce fossil fuel energy and inputs in order to obtain a sustainable agriculture, and plants producing phytochemicals are just one of the several faces of the global issue. However, the complexity of sustainability in phytochemical production does not rely only on agricultural practices. The extraction of natural compounds from plants and their processing requires energy and technology, which weight heavily on both the cost/quality ratio and the environment. Once again, the evident

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contrast between developed and develop ing countries makes the difference in comparative costs. The aim of the present review is to analyze the application of sustainability in the agro-industry of plants producing phytochemicals.by considering separately the several aspects of the problem. MINERAL NUTRITION AND SOIL Since the aim of the present review is sustainable agriculture and the production of phytochemicals, I will not consider the drawbacks of collection of medicinal and aromatic plants from the wild, while focu sing on some aspects of ango-industry. As a personal experience I will give the case of peppermint (Mentha piperita L. ), an aromatic plants which is a rich source of phytochemicals. Peppermint is exten sively cultivated both in temperate and tropical countries (5,6). As for many other plants producing phytochemicals, different transplanting techniques have been applied (fully and partly mechani zed), most of them relying on scantily su stainable practices (7). When dealing with monocultures such as peppermint there is the potential hazard of the suppression of soil fertility, productivity, structure and microbial activity, owing to the continuous cropping. One of the renewable resources on which sustainable agriculture relies is biologically fixed nitrogen. This can be obtained through the use of plants like the legumes in which the biological nitrogen fixation (BNF) occurs in root symbiont diazotrophs. Other than BNF, legumes give other benefits to the soil such as improved nutrient availability, improved structure, reduced pest and disease and hormonal effects through rhyzodeposition (8). Methods to enhance soil productivity

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Sustainable agriculture and phytochemistry

include using of cover crops. Besides crop rotation, intercropping &ives economic and environmental benefits to crops. Soybeans and alfalfa are nitrogen fixers, and can fix 250-400 kg N per hectare per year (9). Peppermint plants intercropped w!t.h soybean require a lesser amount of fertili zers and show a general increase in rno noterpene hydrocarbons and oxygenated compounds such as 1,8-cineole, men thone and menthofuran, whereas the per centage of menthol, isomenthone and menthyl acetate decreases (10). The inter croppi ng practice increases the total amount of phytochemicals produced per surface unit and with an extension of in tercropping cultivation and the setting of machinery able to differentially collect soybeans and plants producing phyto chemicals, besides increased productivity with very low inorganic fertilizers use, there will be the opportunity to obtain subsides for soybean cultivation and the chance to utilize phytochemical plants in sustainable programs with the use of set aside lands. Farmers that cannot switch acreage to conventional crops (wheat, rice, cotton, etc.) without loosing crop acreage base for future price support payment may consider alternatives like phytochemical-producing plant sustain able agriculture programs and plead its application in planting flexibility provi sions present in the farm legislation . Moreover, the legume/phytochemical producing plant intercropping practice can be used in poor fertile soils, to im prove the soil structure and fertility, in crease soil aggregate stability, soil tilth, and diversity of soil microbial life. A healthy soil is the basic of sustaina bility and proper soil management can help prevent some pest problems. In the

cultivation of plants for phytochemicals production, many impairments of soil quality and health result in a reduced pro duction of biomass and oil productivity, while enhancing inputs of water, nutrients, pesticides and energy. Depletion of soil destroys natural predators of crop pests and increases pest spreading as it will be discussed in the next section . PESTS AND PATHOGENS Many plants that produce phytochemi cals are affected by a number of pests and pathogens (II). The continuous and un sustainable use of pesticides and fertilizers in cultural practices increases pest vigour and depletes pest resistance, with increa sing demands for inputs. Besides pathogens, weeds affect phyto chemicals yield by reducing the Nand water availability to producing plants. The struggle against disease and weeds has been brought by the use of pesticides and herbicides, on one hand, and of selected pest resistant crops, on the other hand. In peppermint, the "Murray Mitcham" culti var is widely grown because of its resi stance to Verticillium dahliae (12) and the search for new and pest resistant va rieties continues (10). The finding of new resistant strains gives the opportunity to study the mechanisms of pest resistance. The virulence of a pathogen and the resi stance of a plant are reciprocal concepts, and usually before a pathogen can suc ceed in the infection, it must overcome the plant defensive barriers (13). However, the selection of resistant cultivars is always followed by co-evolution of pathogen races, with altered virulence able to attack and colonize those cultivars that do not retain resistance. In these pathosystems, there is a gene-for-gene relationship of genes defined as resistance

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genes (R), which are present in the host plant and corresponding avirulence genes (avr), which are present in the pat.h?ge~. This means that pathogen recogrution IS determined by the interaction of R genes of the plant host with single avr genes of the pathogen (14). Thus, the sequence data of R genes helps to defin~ ~hose portions of proteins t.hat are spe~I~lc for indi vidual avr determinants, providing an important background for the design of novel resistance traits, in full agreement with the rules of the sustainable struggle against pathogens (15). Tw? other important noteworthy mechanisms of defence are: 1) the systemic acquired resistance (SAR), in which the resistance to a pathogen attack is expressed locally at the site of infection but also systemically, in tissues far away from the initial infection (16); and 2) the hypersensitive response (HR), which leads to a rapid cell (and pathogen) death while inducing a series of biochemical re sponses such as synthesis ?f p.hytoalex!ns, lignin and/or hydroxyprolin-rich prot~ms, transcription of genes for the synt.hesis .of hydrolytic enzymes and an~lmlcrobl~1 polypeptides (17). The selection of resi stant plants producing phytochemicals and the transfer of resistance to high qua lity/high yield not-resistant strains is one of the goals of sustainable agriculture. This can be achieved by the use of natu rally evolved defence mechan~s!ll~' while maintaining the ecosystem equilibrium. The use of pesticides is not banned by sustainable agricultural programs, on~y they have to be used when the econoIl;llc threshold of damage is reached, the point when the damage caused by the pest ex ceeds the costs of chemical control. The inappropriate use of pesticides ~ot only is potentially harmful to the environment,

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but force farmers to depend on them eventually weakening agriculture's eco nomic sustainability. Sustainable approa ches are the least toxic and least energy intensive, while maintaining productivity and profitability . Besides pesticides, biological control of pests is growing rapidly in the modern agricultural practice of biological struggle. Integrated pest management (lPM) is a sustainable approach to managing pests by combining regular scouting and bio control use of living organisms to fight pests with cultural, physical and chemical tools to minimize economic, health and environmental risks. This practice is based on antagonistic interaction between a non-pathogenic organism and a plant pathogen . Even though irnmuno-com promised persons may be sensitive to biological pesticides and therefore be par ticularly vulnerable (18), the use of bio pesticides is surely toward a sustainable use of natural pathogen enemies. Plants producing phytochemicals are also host to many arthropods, both harmful and beneficials. The adequate management of insects and mites is based on several IPM practices such as identification of bene ficial and harmful organisms, protection of beneficial insects and mites and adequate use of pesticides. A careful identification of pest/non-pest insects prevents needless use of pesticides, lowers input costs, pro tects the environment and delays the development of pesticide resistant strains. Another goal of sustainable agriculture is to implement the use of natural sub stances to fight pathogens. Several phyto chemicals have been studied for their biological activity, including antioxidant, antibiotic and antimutagenic properties. An increased concentration of phyto chemicals in tissues particularly sensitive

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to pathogens may prevent the occurrence of disease, the spreading of harmful in sects and inhibition and/or reduction of spore germination of pathogenic fungi. PHYTOCHEMICALS AND THE ENVIRONMENT Plasticity is shown by a genotype when the expression of its individual characte ristics is changed by environmental in fluences, Since all changes in the charac ter of an organism which are not genetic are environmental, plasticity is applicable to all intragenotypic variability (19). The changing composition in phytochemical production from season to season is cle arly a plastic phenomenon which has been thoroughly studied in many genera including the genus Mentha, which shows a great variability in the oil chemical composition according to the place of .cultivation (20-22). Environmental stresses come in many forms , and the most common is the lack of water. In many cases it has been demonstrated that arid soils exert an influence on the chemical composition of phytochemicals (6, and refs. therein). As a natural response to a stress condition, plants react by increasing their defence, for the lack of water is also perceived by insects and animals, which feed on plants also as a source of water. Many cultivated crops exhibit excellent tolerance to environmental stresses by accumulating metabolites of various chemical nature such as nitrogen-containing compounds (proline, other amino acids, polyamines and quaternary amino compounds) , hydroxyl compounds (sucrose, polyols and oligosaccharides) and terpenoids (23,24). In plants producing phytochemicals, the knowledge of the biochemical and molecular mechanisms

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of environmental stresses tolerance is important, owing to the high degree of phenotypic plasticity in the expression of genes involved in the synthesis of the va rious compounds. The selection and use of xeric tolerant condition strains will reduce soil salinity due to extensive irrigation, thus improving the quality of the environment, whereas temperature stress resistant and daylength independent varieties will allow cultiva tion in areas (including those of develo ping or underdeveloped countries) where high temperatures and short days do not allow the cultivation of some phytochemi cal producing plants. Of course, the com plex polygenic responses of plants to en vironmental conditions are still far to be deciphered and controlled , but new and sophisticated tools are available (i .e., DDRT-PCR, see below) to try to face the problem. The sustainable utilization of biochemistry and genetics for the intro duction of new selected plants may lead to an equally expressed chemical com position, no matter the cultivating country, with reduced use of energy, pesticides and irrigation, with a concomitant levelling of cost/quality ratios. BIOTECHNOLOGY AND SUST AINABILITY Is biotechnology compatible with su stainable agriculture ? A survey of the lite rature indicates the presence of two op posite way of answering this question. On one side, biotechnology is seen as the re sponsible of increased corrunercialization of food production, in competition with food for home use. The enhanced market competitiveness caused by biotechnology is supposed to decrease world food secu rity, to create a gap between rich and poor

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countries, to increase poverty, to decrease the ability to protect the environment and to lead to greater need for militarization to maintain order (25). On the other side, biotechnology is considered a useful tool to provide solutions to specific problems in sustainable agriculture. The important point being the correct understanding of biotechnology and its application. Owing to the peculiar characteristic of biotechno logy, it can be of no help to sustainable agriculture in short term. Its utility increa ses in medium terms and is of high use fulness in long terms, where it becomes a starting point for sharp breeding programs in sustainable agriculture (26). With regards to plants producing phy tochemicals, the biotechnological appro ach can be summarized in three points: (i) increasing crop productivity and phyto chemicals yield; (ii) increasing pest resi stance; and (iii) increasing environmental stress tolerance. Increasing crop productivity is a matter of both agronomy and plant physiology. In terms of biotechnology, the recent ad vances on the deciphering of the several genes involved in the photosynthetic pro cess allowed the creation of mutants with improved photosynthetic capabilities. C3 plants that suffer of high levels of photo respiration, that clearly reduce the poten tial ability to fix carbon, can be geneti cally transformed to decrease photorespi ration and/or enhance photosynthesis via site directed mutagenesis or antisense te chnology (see below). Transgenic plants can then be obtained and used for sustai nable agriculture programs in order to improve productivity. The increasing phytochemicals yield is a matter of both biochemistry and plant morphology. From a biochemical point of view, increasing yield means the overex

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pression of some genes involved in the secondary metabolism and the complete conversion of by-products whose accu mulation lowers the content of quality compounds. From a morphological view point, several phytochemicals accumulate in specialized tissues such as secretory structures. To produce new biological structures (i.e. more producing secretory tissues) and/or functions (enhanced en zyme activity) , the traditional plant breed ers used crossing and backcrossing proto cols. Now, genetic engineers manipulate at the DNA level the information avail able in biological systems in an attempt to increase the speed at which new biologi cal structures and functions are produced, by short-cutting sexual reproduction and by-passing limits the traditional breeders face. Genetic engineering is considered in sustainable agriculture as far as its possi ble effects on the stability of the biosphere are under control (4). Increased pest resistance involves the transfer of genes from pest resistant varie ties to non resistant ones. The biggest task is, as mentioned above, the identification, coding and transfer of resistance genes to non resistant plants. One of the most re cent acquisition in the identification of genes expre ssed under stress is the Differential Display Reverse Transcription - Polymerase Chain Reaction (DDRT-PCR) (27) in which only nanograms of total RNA are sufficient, enabling to investigate every single mRNA species expressed in the cells under different stress situations, even those expressed at very low levels. Moreover this technique detects up regulation and down-regulation of genes at the same time, it is very fast (less than three days to isolate and reamplify differentially expressed genes) and can


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The major risk of applying resistance gene transfer is the development of pest resistance in weeds though gene flow via pollination. This is particularly important when herbicide-tolerant traits are transfer red to crops. The case of sterile plants is quite particular, since these crops are re produced vegetatively, but the risk is high in sexually reproducing plants.

technology uses the gene encoding one of these enzymes in the reverse orientation and hooked to a control region that di rects gene expression in whatever organ or tissue of the plant is desired. The results is the slowing down of senescence and the same goal can be also achieved transforming plants with a gene that degrades ACC as soon as it is formed (9). Same technology can be applied to those plants producing phytochemicals in order to reduce senescence and the related changes in the phytochemical composition.

The resistance to environmental stresses can be achieved by identifying the gene s responsive to the major factors which alter the quality and content of the phytochemicals produced. The control of day length response of many plants producing phytochemicals will allow cultivation of the transformed genotypes in countries were the actual limit of cultivation is the temperature and light response of the plant. The identification of genes responsive to temperature and to plant development will allow the control of phytochemical s quality non only during seasonal changes but also in the different plant organs . With regard senescence, in many crops the age of the plant is accompanied with the changing in phytochemical composi tion. Many genes concur in the sene scence process and senescence is control led by the balance between the two hor mones auxin and cytokinins and the hor mone ethylene. Genetic engineering to alter senescence involves the suppression of ethylene synthesis by antisense techno logy of the genes that encode the two en zymes involved in the hormone synthesis, aminocyclopropane carboxylic acid (ACC) synthase and ACC oxidase. This

Once again. the correct and wise use of biotechnology can improve our knowl edge on gene responses to environmental changes, but we cannot ignore that any achievement has to be faced in normative terms. This norm relies again in the tenns of sustainable agriculture that weights the present aspiration for a continuos increase of the standard of living and the right of future generations to live in a suitable en vironment. Among these norms it lies also the cultural implications that the making of new transgenic plants generate. The in crease in patenting new transgenic organ isms tends to increase the growing opin ion of organisms as tools (machines) used to produce goods and not as members of the biosphere. This leads to an economic engagement towards the creation of new transgenic organisms and a depletion of funds devoted to the understanding of the many aspects we still ignore about the natural life forms. If there is a reason for unsustainability in biotechnology. then this reason has to be seen in the distortion of allocation of funds for basic research. If there is sustainability in biotechnology. this will be the extremely powerful poten tial that this practice has to understand the secrets hidden in the genomes of already

utilize nonradioactive methods (28) . This technique has been already successfully used for the analysis of differential gene expression in plant-fungus interactions (29).

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existing plants. IN VITRO CULTURES

Plant cell and tissue cultures are the base for any biotechnological application. The in vitro studies on plants producing phytochemicals started in the sixties with the aim of both producing phytochemicals and obtaining plant material for further genetic transformation (30). In some cases, the failure to produce phytochemicals in vitro in a quantity comparable or superior to that obtained from plants grown in field depends on both the presence of highly differentiated secretory tissues (i.e., the glandul~r trichomes), which are not produced III undifferentiated cell suspensions and the high requirement for carbon allocation to secondary metabolite synthesis. In peppermint callus and cell cultu.res the essential oil yield is very low and 1S often characterized by the presence of high percentages of undesired compounds (i.e., menthofuran and pulegone instead of menthone and menthol). In some case the stimulation of callus cultures with colchicine increased up to 3-fold the es sential oil yield owing to the neo formation of glandular trichomes on calli (30). Moreover, the subculturing of plants obtained from explants of nodal segments may lead to different phenotypic expres sions with resulting dramatic changes in phytochemical composition (31). The finding that some cell cultures are able to biotransform phytochemicals prompted a series of investigations on both suspen sion and immobilized cell systems, with increased recovery of useful compounds, the reduction of undesirable reactions and potential applications for large scale pro duction in bioreactors (31,32). Besides in vitro production of phyto

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che micals, one of the most interesting application of cell and tissue culture is in breeding programs. For some sterile plants the breeding by common crossing methods is impossible unless the ploidy is doubled for fertility (33). The technique of cell fusion from protoplasts is one of the mo st promising one in breeding pro grams, allowing to overcome the impair ing of incompatible crossing and to gene rate somaclonal/protoclonal variation. Furthermore, Ag robacterium tumefa d ens-mediated transformation of plants producing phytochemicals has been ob tained demonstrating the potential for us ing plasmid transfer to obtain transgenic plants carrying economically important genes (34). These techniques are not in disagreement with sustainable agricultural methods. By improving the knowledge on the natural resources without compromis ing or endangering the biodiversity of species under study, they can be conside red a quick and valuable tool to improve crops without compromising the envi ronment. In vitro obtained strains can also be used for pest control programs. Meristematic virus-free and pathogen-free parts can be explanted for micropropaga tion to obtain healthy plants. Direct shoot and root regeneration can be obtained with appropriate hormonal application and pest-free plants can be transplanted to the field. In the case of peppermint, such applications allowed 4.9 and 3.5 increa ses in the harvest in the first and second year of peppermint regenerated plants, re spectively, with increased menthol con tents as well (35). As stated, the goal of sustainable agri culture is the elimination of agronomic practices that lead to environment degra dation and to minimize inputs. If plant, cell and tissue culture studies will lead to


these two objectives then there will be a chance for a sustainable use of in vitro breeding programs based on genetic transformation. But if this will lead to im proved high input agro-industry afforda ble only by developed country, then there will be a scantily sustainable future for the biotechnological approach for the cultiva tion of plants producing phytochemicals. Developing and underdeveloped coun tries whose potentials for phytochemical producing plants cultivation are increas ing will not be able to sustain high-input agronomic conditions and they will be forced (or obliged) to perpetuate the pre sent agricultural and often not sustainable systems . The recent advances in genetics and biochemistry of secondary metabolites can furnish a valuable tool for biotechno logical applications, but in vitro large scale production of phytochemicals is not always sustainable in short and medium terms. High-input biotechnology is parti cularly useful when secondary plant pro ducts derive from endangered or very low yielding species (i.e. , Catharanthus ro seus, Taxus brevifolia, etc.), or whose products are quite expensive (i .e., jas mine) (9). Some plants like peppermint do not fall into these categories and in case of biotechnological approaches these should be toward improved genetic resi stance to stresses and pests, to increased crop productivity and decreased nutrient and water demands, more than in vitro production of phytochemicals. The production of phytochemicals by cell culture has a profitable future if directed towards those chemicals that will open new markets by favouring the development of cheaper and sustainable production processes (9).

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EXTRACTION OF PHYTOCHEMICALS The last link in the sustainable chain for a sustainable agriculture in phytochemical production is the extraction process. The extraction requires energy with resulting different cost/benefit ratios according to the country of cultivation. Developed low cost fossil-fuel utilizing countries (i.e., U.S.A.) use high-input technologies, which are adopted by countries (i.e ., many European countries) for which there is a high cost for fossil fuel, with consequent higher cost/quality ratios. Developing countries, on the other hand, use organic-fuel and more low-costly human power, with consequent deforestation, air pollution and environment and human degradation. In developing and underdeveloped countries, the cost/benefit ratio is usually kept low often at the expenses of product quality. In many cases, the process often consumes energy and pollutes the envi ronment by the generation of fuel-derived gases, by the use and dispersal of water and by the dumping of spent material after extraction. In the case of peppermint, a global overview on the distillation processes adopted by the mint growers indicates the U.S.A. system to be the most efficient, in terms of high-input agriculture. The less efficient systems are those based on old family tradition technologies, which use distillers and harvesting/collecting techno logies handed on from father to sons without consistent improvements. From grower to grower, in some developed countries (as in Europe) there is a great difference in the time of harvesting, hol ding the harvested material in the field (more or less dry material to be distilled) and distilling the plant material. Quite of

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ten, the distillers are old apparatuses with a low yield and a consistent dispersal of thermal energy and essential oil into the environment. Eventually, the lack of sub sides for extraction improvement leads many growers to give up phytochemical producing plant cultivation in favour of staples like wheat and corn. In the U.S. system the appropriate balance between mechanization of peppermint harvesting and then collection into distilling tubs on one side, and the multiple steam condenser systems on the other side, allows both ,reduction of the cost/benefit ratio and the improvement (constancy) of distilled oil quality. The transportable tub allows cultivation of peppermint far away from the distillers and gives the opportunity of peppermint cultivation without the owning of distillers. Th is is the sustainable aspect of the U.S. system, which reduces the dispersal of energy in several distillers and concentrates the process in few distilling centres. With the adoption of improved distillers , able to utilize a reduced amount of fossil-fuel deri ved energy and to recover most of the hot water coming from the condensers (for example, to pre-heat the tubs), the use of alternative energy sources (most of the distillation is performed during the sun niest season) and environmentally-friend cooling gases to improve condensation, there will be a chance for a sustainable future in the distillation process of pep pennint and other aromatic plant oils. The last problem remains the plant ma terial which is dispersed in the environ ment. Often in these plant residues are still present many phytochemicals and the leaching of these substances in the soil may perturb the natural biosphere soil equilibrium. The problem is particularly evident in those countries with restrictions

in land availability . Adding fresh organic matter to the soil tends to boost plant growth less quickly than adding compost, which is organic matter partly decomposed by microrganisms and soil fauna. The spent material coming from extraction of phytochemicals could be composted through processing with bacteria and/or fungi able to degrade phenolics and other soil interacting compounds, thus reducing soil contamination and pollution due to lea ching. Many microrganisms degrade phe nolics by the synthesis of extracellular en zymes (i.e. lignin peroxidase), while other soil microrganisms convert other complex compounds into soluble products that can be taken up by plants and soil animals (9 ). The making of compost from spent material is one of the many goals for a sustainable agriculture in phytochemical production. CONCLUDING REMARKS Only a sustainable practice in agricul ture will allow next generations to enjoy the goods we are enjoying. This requires a commitment to changing public poli cies , economic institutions and social va lues , and phytochemicals production is part of the whole problem. There's a trait d'union between the restrictive organic farming and the high-input agriculture, it is sustainable agriculture. Many problems have still to be solved in the sustainable agricultural practices such as lack of ef fectiveness, lack of information, manage ment complexity, scarce availability of biological agents, high labour require ment, lack of regulatory concerns and still . high costs. Moreover, it is not known to what extent will the farmers be willing to sacrifice predictable short-term profits for the unpredictable rewards of environmen


tal stewardship. All these problems lower the run toward sustainability and the availability of funds for sustainable agri culture research in favour of the more short term profitable high-input agro-in dustry. But this is a battle we must fight in terms of nutrient and energy dynamics, and interaction among plants, animals and microrganisms, balancing it with profit, community and consumer needs. The search for pest's natural enemies, the adoption of alternative agricultural methods, the deciphering and the transfer of genetic information to improve phyto chemicals yield and the resistance to bio tic and abiotic stresses through biotechno logy and in vitro systems, and the reduc tion of environmental pollution by the im provement of the extraction system will allow a sustainable agriculture in phyto chemistry for a sustainable future in deve loped, developing and underdeveloped countries.

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