Plant cell cultures: Chemical factories of secondary metabolites

Photosynthesis is the incorporation of carbon, nitrogen, sulphur and other substances into plant tissue using light energy from the sun. Most of this energy is used for the reduction of carbon dioxide and, consequently, there is a large body of biochemical and biophysical information about photo synthetic carbon assimilation. In an ecophysiological context, we believe that most of today’s biochemical knowledge can be summarized in a few simple equations. These equations represent the rate of ribulose bisphosphate (RuP2)-saturated carboxylation, the ratio of photorespiration to carboxylation, and the rates of electron transport/photophosphorylation and of “dark” respiration in the light. There are many other processes that could potentially limit CO2 assimilation, but probably do so rarely in practice. Fundamentally this may be due to the expense, in terms of invested nitrogen, of the carboxylase and of thylakoid functioning. To reach our final simple equations we must first discuss the biochemical and biophysical structures — as they are understood at present — that finally reduce the vast number of potentially rate-limiting processes to the four or five listed above. A diagrammatic representation of these processes is given in Fig. 16.1.

Modelling of Photosynthetic Response to Environmental Conditions

A substantial number of micropropagated plants do not survive transfer from in vitro conditions to greenhouse or field environment. The greenhouse and field have substantially lower relative humidity, higher light level and septic environment that are stressful to micropropagated plants compared to in vitro conditions. The benefit of any micropropagation system can, however, only be fully realized by the successful transfer of plantlets from tissue-culture vessels to the ambient conditions found ex vitro. Most species grown in vitro require an acclimatization process in order to ensure that sufficient number of plants survive and grow vigorously when transferred to soil. This article reviews current and developing methods for the acclimatization of micropropagated plantlets.

Acclimatization of tissue cultured plants

Activated charcoal is commonly used in tissue culture media. Its addition to culture medium may promote or inhibit in vitro growth, depending on species and tissues used. The effects of activated charcoal may be attributed to establishing a darkened environment; adsorption of undesirable/inhibitory substances; adsorption of growth regulators and other organic compounds, or the release of growth promoting substances present in or adsorbed by activated charcoal.

The use of charcoal in in vitro culture – A review

I From Metabolism and Osmotic Work to Totipotency and Morphogenesis: A Study of Limitations Versus Multiple Interactions.- II Primary Metabolism.- Photosynthetic Carbon Metabolism in Photoautotrophic Cell Suspension Cultures of Chenopodium rubrum L..- On the Photosynthetic System and Assimilate Metabolism of Daucus and Arachis Cell Cultures.- Regulation of Carbon and Nitrogen Assimilation Pathways in Tobacco Cell Suspension Cultures in Relation with Ultrastructural and Biochemical Development of the Photosynthetic Apparatus.- Application of Gas Analysis to Continuous Culture.- Carbohydrate Source, Biomass Productivity and Natural Product Yield in Cell Suspension Cultures.- Nitrogen Metabolism of Leaf and Microspore Callus of Betula pendula.- III Secondary Metabolism.- 4-Coumarate: CoA Ligase in Wild Carrot Cell Culture Clones Which Accumulate Different Amounts of Anthocyanin.- Induction of Anthocyanin Synthesis in Relation to Embryogenesis in a Carrot Suspension Culture - A Model System for the Study of Expression and Repression of Secondary Metabolism.- Metabolism of Quinolizidine Alkaloids in Plants and Cell Suspension Cultures: Induction and Degradation.- Production of Alkaloids by Ergot (Claviceps fusiformis Lov.) on Pennisetum typhoides (Burm.) Stapf and Hubb. in Vitro.- Compartmentation of Alkaloids in a Cell Suspension of Catharanthus roseus: A Reappraisal of the Role of pH Gradients.- Studies on Variability of Plant Tissue Cultures for Alkaloid Production in Catharanthus roseus and Papaver somniferum Callus Cultures.- Biosynthesis and Accumulation of Indole Alkaloids in Cell Suspension Cultures of Catharanthus roseus Cultivars.- Formation of Cardenolides in Cell and Organ Cultures of Digitalis lanata.- Metabolism of Caffeoyl Derivatives in Plant Cell Cultures.- Metabolic Relationships of Putrescine, GABA and Alkaloids in Cell and Root Cultures of Solanaceae.- Metabolism and Degradation of Nicotinic Acid in Plant Cell Cultures.- Plant Cell and Tissue Culture of Cinchona Species.- The Production of Pyrethrins by Chrysanthemum cinerariaefolium (Trev) Bocc..- Biosynthesis of Chorismate-Derived Quinones in Plant Cell Cultures.- The Role of Leucine in Terpenoid Metabolism: Incorporation of Leucine into Sesquiterpenoids and Phytosterols by Andrographis Tissue Cultures.- Accumulation of Antineoplastic Agents by Plant Tissue Cultures.- Induction of Enzymes of Phytoalexin Synthesis in Soybean Cells by Fungal Elicitor.- Protoplast Fusion of Secondary Metabolite-Producing Cells.- Conventional and New Approaches to Increase the Alkaloid Production of Plant Cell Cultures.- Multiple Shoot Cultures: A Viable Alternative in Vitro System for the Production of Known and New Biologically Active Plant Constituents.- IV Fermentation and Cryopreservation.- Large-Scale Production of Rosmarinic Acid from Plant Cell Cultures of Coleus blumei Benth..- Immobilised Plant Cell Culture Systems.- Biotransformation of Cardiac Glycosides by Digitalis Cell Cultures in Airlift Reactors.- Cryopreservation of Plant Cell Cultures.- V Herbicides.- Altered Amino Acid Biosynthesis in Amino Acid Analog and Herbicide-Resistant Cells.- Acetohydroxyacid Synthase Inhibitors as Herbicides.- A Glyphosate-Tolerant Plant Tissue Culture.- VI Plant Cell Culture - Future Perspectives.

Primary and secondary metabolism of plant cell cultures

Tissue cultures of Lilium auratum Lindl and L speciosum Thunb, which were derived from bulbscales, all appeared to differentiate organs The effect of cultural conditions on the differentiation of bulblets and roots was examined

The best material for bulblet formation was bulbscales of intact or in vitro produced bulblets The optimum temperature was 20°C and optimum pH was 6 Effect of irradiance on organ formation was not obvious but leaf emergence was stimulated

Higher kinetin concentrations stimulate the formation of numerous bulbscalcs High NAA concentrations induce roots On the other hand kinetin inhibits the NAA effect on root formation A high sucrose concentration stimulated organ formation, but the number of bulblets was at a constant level in the medium containing between 10 and 90 g/l of sucrose The formation of bulblets and their growth were stimulated at increasing strength of Murashige-Skoog's (MS) medium, but the length of roots was inhibited Inter action of strength of MS medium and sucrose concentration was examined High concentration of both components stimulated bulb lei growth, but the second strength of MS medium containing 90 or 120 g/l sucrose stimulated callus induction and inhibited the growth of bulblets

Maximum growth took 100 days for bulblets and about 50 days for roots The change of fresh weight/dry weight ratio during differentiation is also discussed

Differentiation in Lilium Bulbscales Grown in vitro. Effect of Various Cultural Conditions

Organ differentiation and growth of tissue cultured bulbscales of Lilium auratum Lindl. was investigated. Benzyladenine stimulated bulb and bulbscale differentiation but inhibited root formation. Addition of activated charcoal to the medium negated the effect of BA on differentiation, while the growth of bulbs was markedly stimulated. Organ formation was also influenced by the physiological age of bulbs. From bulbscales of a 3-week-old bulb, a large number of bulbs and roots was formed but callus was not produced.



A high sucrose concentration (90 g/1) reduced the subsequent sprouting after planting in soil. Scale leaf formation was also regulated. Sucrose (30 g/1) stimulated scale leaf formation but 90 g/1 were inhibitory.

Differentiation in Lilium bulbscales grown in vitro. Effects of activated charcoal, physiological age of bulbs and sucrose concentration on differentiation and scale leaf formation in vitro

Shinsaku Takayama

Papers

Differentiation in Lilium Bulbscales Grown in vitro. Effect of Various Cultural Conditions

Differentiation in Lilium bulbscales grown in vitro. Effects of activated charcoal, physiological age of bulbs and sucrose concentration on differentiation and scale leaf formation in vitro

Mass Propagation of Begonia × hiemalis Plantlets by Shake Culture :

A scheme for mass propagation of Lilium in vitro

Regulation of Organ Formation by Cytokinin and Auxin in Lilium Bulbscales Grown In Vitro