Influence of temperature on alkaloid levels and fall armyworm performance in endophytic tall fescue and perennial ryegrass

The symbiotic relationships between Neotyphodium endophytes (Clavicipitacea) and certain cool‐season (C3) grasses result in the synthesis of several alkaloids that defend the plant against herbivory. Over a 3 month period we evaluated the effects of temperature on the expression of these alkaloids in tall fescue, Festuca arundinacea Schreb, and perennial ryegrass, Lolium perenne L. (Poaceae). Response surface regression analysis indicated that month, temperature, and their interaction had an impact on the alkaloid levels in both grasses. We aimed to identify the alkaloids most closely associated with enhanced resistance to the fall armyworm, Spodoptera frugiperda JE Smith (Lepidoptera: Noctuidae), and clarify the role of temperature in governing the expression of these alkaloids. The dry weights and survival of fall armyworms feeding on endophyte‐infected tall fescue or perennial ryegrass were significantly lower than for those feeding on uninfected grass, whereas endophyte infection had no significant influence on survival. For tall fescue, a four‐alkaloid model consisting of a plant alkaloid, perloline, and the fungal alkaloids ergonovine chanoclavine, and ergocryptine, explained 47% of the variation in fall armyworm dry weight, whereas a three‐alkaloid model consisting of the plant alkaloid perloline methyl ether and the fungal alkaloids ergonovine and ergocryptine explained 70% of the variation in fall armyworm dry weight on perennial ryegrass. Although temperature had a significant influence on overall alkaloid expression in both grasses, the influence of temperature on individual alkaloids varied over time. The levels of those alkaloids most closely linked to armyworm performance increased linearly or curvilinearly with increasing temperature during the last 2 months of the study. We conclude that the growth temperature of grasses can influence the performance of fall armyworm, and that this effect may be mediated through a set of plant‐ and endophyte‐related alkaloids.     

Cutting reduces variation in biomass production of forage crops and allows low‐performers to catch up: A case study of Trifolium pratense L. (red clover)

• Re‐growth of fodder plants after grazing and mowing drives the profitability of their cultivation and is therefore an important target trait for plant breeding and agricultural engineering. However, for some fodder plants little is known about their re‐growth dynamics in response to grazing or mowing.
• We analysed the native response of plant architecture, leaf morphology and growth performance to experimental cutting in wild Trifolium pratense L. (red clover) plants. A total of 150 potted clover plants were established under controlled field conditions, and half of the plants were cut to 5 cm 3 months after sowing. Each plant was measured every week for 5 months.
• The cut and subsequently re‐grown plants carried fewer main branches (?20%), as well as fewer (?13%) and smaller (?32%) leaves than the control plants. However, the cut plants produced an average of 17% more accumulated leaf area (cut + re‐grown leaf area) than the control plants. This discrepancy was explained by variation in the growth strategy of the plants, where the cut plants invariably expressed a second growth phase, while almost half of the untreated plants did not.
• Our results suggest that cutting acted as an artificial trigger initiating a second growth phase in the cut plants and thereby contributed to yield increase. Exploiting this mechanism may set new goals for breeding and optimisation of the mowing regime.

     

Controlling invasive Arrhenatherum elatius and promoting native prairie grasses through mowing

Abstract. Control of invasive plants is a key element of conservation and restoration efforts. We report results from a five‐year field experiment in western Oregon, USA that evaluates the effects of different mowing regimes on the non‐native and invasive perennial grass Arrhenatherum elatius, the native perennial prairie grasses Danthonia californica and Festuca roemeri, and groups of other native and non‐native grasses and forbs. Eight treatments were designed to test hypotheses about the role of mowing height and time of application on the plant community. Differences among treatments emerged only after two or three years of treatment. This delay in response reinforces the need for long‐term studies. Annual mowing was most effective at reducing Arrhenatherum cover and flowering when applied in late spring or early summer, the time of Arrhenatherum flowering and expected maximum above‐ground allocation. Double mowing and mowing at 15 cm were more effective in reducing Arrhenatherum cover than were single mowing and mowing at 50 cm. All treatments increased the cover and flowering of Danthonia. Statistical model analysis showed that increases in cover and flowering of the native grass Danthonia were caused by its release from suppression by Arrhenatherum. Fouryears of the most effective treatment, mowing at 15 cm in late spring, converted an Arrhenatherum‐dominated site to a prairie dominated by native grasses. This is one of the few documented cases of pest plant control causing an increase in native plant abundance. These results show that mowing, properly applied, can be an effective tool for restoring degraded, Arrhenatherum‐dormnated prairies.     

Influence of gibberellic acid on <Superscript>14</Superscript>CO<Subscript>2</Subscript> metabolism,growth, and production of alkaloids in <Emphasis Type="Italic">Catharanthus roseus</Emphasis>

Changes in growth parameters, carbon assimilation efficiency, and utilization of ¹⁴CO₂ assimilate into alkaloids in plant parts were investigated at whole plant level by treatment of Catharanthus roseus with gibberellic acid (GA). Application of GA (1 000 g m⁻³) resulted in changes in leaf morphology, increase in stem elongation, leaf and internode length, plant height, and decrease in biomass content. Phenotypic changes were accompanied by decrease in contents of chlorophylls and in photosynthetic capacity. GA application resulted in higher % of total alkaloids accumulated in leaf, stem, and root. GA treatment produced negative phenotypic response in total biomass production but positive response in content of total alkaloids in leaf, stem, and roots. ¹⁴C assimilate partitioning revealed that ¹⁴C distribution in leaf, stem, and root of treated plants was higher than in untreated and variations were observed in contents of metabolites as sugars, amino acids, and organic acids. Capacity to utilize current fixed ¹⁴C derived assimilates for alkaloid production was high in leaves but low in roots of treated plants despite higher content of ¹⁴C metabolites such as sugars, amino acids, and organic acids. In spite of higher availability of metabolites, their utilization into alkaloid production is low in GA-treated roots.     

Structural Characterisation of Alkaloids in Leaves and Roots of Stephania kwangsiensis by LC‐QTOF‐MS

Introduction

The tuberous roots of Stephania kwangsiensis, which contain bioactive alkaloids, are used as a traditional Chinese medicine. Overexploitation of the roots has made the plant increasingly rare, and the abundant leaves of the same plant may offer a potential alternative. However, there is insufficient phytochemical information for a comparison of alkaloid compositions in the two parts.

Objective

To characterise and compare the alkaloids in the leaves and roots of S. kwangsiensis.

Methods

The alkaloids in S. kwangsiensis were characterised using high pressure liquid chromatography coupled with positive electrospray ionisation quadrupole time‐of‐flight tandem mass spectrometry (HPLC‐(+)ESI‐QTOF‐MS/MS). The alkaloid compositions in the leaves and roots were compared by visual inspection combined with principal component analysis (PCA) of the HPLC‐MS data.

Results

Seventy‐five alkaloids comprising aporphine‐, proaporphine‐, protoberberine‐, benzylisoquinoline‐, bisbenzylisoquinoline‐ and morphine‐type alkaloids were identified or tentatively identified in the roots and leaves of S. kwangsiensis. Sixty‐three of these alkaloids have not been previously reported in this species, and three have not been previously reported in the literature. The roots and leaves had similarities in alkaloid composition but differences in the peak intensities of most alkaloids. The PCA revealed that the samples were clustered into two distinct groups, which corresponded to leaves and roots.

Conclusion

This study further clarified the chemical constituents in the roots of S. kwangsiensis, and revealed that diverse alkaloids were also present in the leaves. The comparative chemical profiling of the two parts provides useful information on their potential medicinal use. Copyright © 2017 John Wiley & Sons, Ltd.     

Biogeographical Patterns and Phenological Changes in Lapiedra martinezii Lag. Related to Its Alkaloid Diversity

The aim of this work was to investigate the alkaloid patterns of Lapiedra martinezii and their relation to biogeography and phenology focused in a phylogenetic comparison. Plants from 14 populations of L. martinezii, covering almost its entire distribution area, were subjected to morphological, ecological, and phytochemical analysis. Experiments for different alkaloid‐type content are proposed as a new tool for analysis of plant distribution. Several plants were transplanted for weekly observation of their phenological changes, and alkaloids from different plant organs were extracted, listed, and compared. The alkaloid pattern of L. martinezii comprises 49 compounds of homolycorine, lycorine, tazettine, haemantamine, and narciclasine types. The populations located in the north and south margins of the distribution area displayed alkaloid patterns different from those of the central area. Changes in these patterns during their phenological cycle may be related to a better defence for plant reproduction. L. martinezii is an old relict plant, and it has maintained some of the more primitive morphological features and alkaloid profiles of the Mediterranean Amaryllidaceae. The variations in alkaloid content observed could be interpreted in a phylogenetic sense, and those found in their phenological changes, in an adaptive one.     

Growth and alkaloid contents in leaves of Tabernaemontana pachysiphon Stapf (Apocynaceae) as influenced by light intensity,water and nutrient supply

The growth of Tabernaemontana pachysiphon (Apocynaceae) plants and the alkaloid content of leaves were investigated in the greenhouse at three levels of nutrient supply under two contrasting water and light regimes. We determined height increment, above-ground biomass production, leaf size, specific leaf weight and the content of the alkaloids apparicine, A2, isovoacangine, tubotaiwine and tubotaiwine-N-oxide. The effects of major controlling factors such as light, water and nutrient supply could be directly correlated with growth and were largely independent of each other. In contrast, leaf-alkaloid contents were influenced by interdependencies among the main factors and individually affected in a synergistic or antagonistic manner which deviated from the effects on growth. The following general trends could be identified with respect to the quantitatively predominant alkaloids apparicine, tubotaiwine and isovoacangine. Increasing nutrient supply had a positive effect on both growth and alkaloid content. Drought increased alkaloid content, but retarded growth. High light intensity lowered alkaloid content but promoted growth. We investigated the relationship between primary production and the production of secondary metabolites with respect to relative and total alkaloid content as well as in relation to the leaves' nitrogen status. Our results showed that under conditions of low nutrient supply, higher proportions of leaf nitrogen were allocated to alkaloids than at moderate or high nutrient supply. Under conditions of drought and low light, all plants allocated almost equal proportions of leaf nitrogen to alkaloids, regardless of fertiliser. Total alkaloid content per plant, however, increased with fertilisation. With respect to the N-allocation strategy, we found no indication of a trade-off between primary production and the production of secondary metabolites in this species. Rather, our results are in accordance with the carbon nutrient balance hypothesis.     

Impact of mowing and weed control on broadleaf weed population dynamics in turf

Abstract

Various turf management activities may influence weed population dynamics and interfere with weed control. The effects of a biocontrol agent, Sclerotinia minor, a chemical herbicide, Killex?, and mowing height on broadleaf weed dynamics were examined in two turfgrass stands for two consecutive years. Mowing did not reduce the population densities of dandelion or the ground cover of broadleaf weeds. In the second year, mowing significantly reduced white clover density, but significantly increased broadleaf plantain density, particularly at the closest mowing height (3–5 cm). Apart from the close height, the S. minor and Killex? treatments were equally effective in suppression of dandelion, white clover, broadleaf plantain, and prostrate knotweed in the second year. Common mallow increased in the herbicide treated plots and other species including yellow woodsorrel, yellow toadflax and lambsquarters increased in abundance in plots mowed at the 3–5 cm height and in plots treated with Killex?. Significant differences between the Killex? and S. minor treatments on dandelion population dynamics were rarely present and did not favour either treatment. S. minor did not damage the turfgrass, but Killex? reduced turf quality in 25% of the plots. The application of S. minor with a regular, medium height (～7 cm) mowing regime was highly effective in controlling broadleaf weeds in temperate Kentucky bluegrass turf.     

Arbuscular mycorrhizal fungi and potassium bicarbonate enhance the foliar content of the vinblastine alkaloid in Catharanthus roseus

Vinca (Catharanthus roseus (L.) G. Don.) is an important medicinal plant species from which antineoplastic alkaloids such as vinblastine are extracted. However, neither abiotic stress nor inoculation of arbuscular mycorrhizal fungi (AMF) has been evaluated on the accumulation of vinca alkaloids under controlled conditions. This study evaluated the effects of AMF and/or abiotic stress induced by the application of potassium bicarbonate (KHCO₃) and/or sodium chloride (NaCl) on plant growth, and on total content of phenolic compounds (TCPC), total antioxidant activity (TAOX), and total content of vinblastine alkaloid in leaves of vinca. TCPC, TAOX, and vinblastine were measured via spectrophotometric methods. After 75 days under greenhouse conditions, either the AMF inoculation without abiotic stress or the application of KHCO₃ (2.5 and 7.5 mM) resulted in significantly (P?≤?0.001) enhanced plant growth, TCPC, TAOX, and total content of vinblastine. The application of NaCl significantly diminished plant growth, but did not stimulate the content of vinblastine. The combined application of NaCl and KHCO₃ significantly decreased AMF-colonization in roots. The sole inoculation of AMF or the single application of 7.5 mM KHCO₃ induced the accumulation of vinblastine in leaves of vinca.     

Alkaloid profile and antimicrobial activity of <Emphasis Type="Italic">Lupinus angustifolius</Emphasis> L. alkaloid extract

Purpose of the present study was to evaluate alkaloid profile of the aerial parts of Lupinus angustifolius growing in Turkey by capillary gas chromatography-mass spectrometry (GC-MS). Fifteen alkaloids were identified by capillary GC-MS. 13α-Hydroxylupanine (50.78%) and lupanine (23.55%) were determined as the main alkaloids in the aerial parts of L. angustifolius. Ammodendrine, isoangustifoline, tetrahydrorhombifoline, angustifoline, α-isolupanine, 5,6-dehydrolupanine, 11,12-dehydrolupanine, 13α-acetoxylupanine, 13α-isovaleroyloxylupanine, 13α-valeroyloxylupanine, 13α-tigloyloxylupanine, 13α-cis-cinnamoyloxylupanine and 13α-cis-cinnamoyloxy-17-oxolupanine were identified as the minor alkaloids of the plant. Furthermore, antibacterial and antifungal activities of L. angustifolius alkaloid extract were tested against standard strains of the following bacteria; Escherichia coli, Pseudomonas aeruginosa, Bacillus subtilis and Staphylococcus aureus as well as the fungi; Candida albicans and C. krusei. The alkaloid extract showed significant activity on B. subtilis, S. aureus and P. aeruginosa while it was weakly active on E. coli. On the other hand, the extract possessed moderate activity against C. albicans and C. krusei.     

Precipitation and mowing effects on highway rights-of-way vegetation height and safety

Managing highway rights-of-way (HROW) for safety depends upon the annual precipitation received and vegetation mowing practices. This study was conducted along a precipitation gradient in Texas, USA, to evaluate how precipitation and mowing treatments influence vegetation heights. The experiment was initiated in spring 1999 and completed in autumn 2002. Each site had ten treatments with four replications and consisted of forty 15 m × 6 m subplots. Commercial highway mowing equipment was used to mow the subplots at 5-, 10-, or 20-cm heights with an annual mowing frequency of one, two, or three times per year and a non-mowed control. A vegetation height of >30 cm is generally considered a safety hazard. Control subplot vegetation heights increased along the annual precipitation gradient. Most of the subplot vegetation heights at the more arid Andrews site (35 cm precipitation year^?1) were <30 cm. Subplot vegetation heights at the Tahoka (50 cm precipitation year^?1), Brady (66 cm precipitation year^?1), and Lufkin (109 cm precipitation year^?1) locations exceeded 30 cm, regardless of mowing frequency or height. Mowing treatments for HROW safety must be based on site-specific conditions. In areas that receive <35 cm precipitation year^?1, mowing treatments have little effect on vegetation height, and management practices do not necessarily affect visual safety. In areas that receive >35 cm precipitation year^?1, mowing three or less times per year, regardless of mowing height, makes it unfeasible to maintain the vegetation heights of <30 cm needed to maintain the HROW visual safety criterion.     

The impacts of increased nitrate supply on Catharanthus roseus growth and alkaloid accumulations under ultraviolet-B stress

It has been reported that nitrate availability was able to modify the detrimental effects induced by excess ultraviolet-B (UV-B) radiation on plants. In this study, the medical plant Catharanthus roseus was subjected to UV-B stress and altered levels of nitrate nutrition to investigate their influence in a sole or combined way on growth and alkaloid productions. Our results showed that the UV-B stress obviously inhibited growth and led to damages of oxidative stress and lipid peroxidation. The simultaneous supply of higher nitrate nutrition could largely alleviate the inhibitory effects and damage symptom under the UV-B stress in C. roseus. Meanwhile, the UV-B-absorbing compounds as well as three alkaloids, vinblastine, vindoline, and catharanthine, were observed to have a remarkable elevation. These compounds were considered to serve as protectants of UV-B radiation. It was concluded that an increased nitrogen (N) supply could not only alleviate the inhibitory effect of UV-B stress on plant growth, but also enhance the accumulation of pharmaceutically used alkaloid in these plants. We proposed that the enrichment of N nutrition might provide more N source for alkaloid synthesis induced by UV-B radiation, eventually resulting in an increase of alkaloids accumulation.     

不同刈割频度对大针茅草原群落特征及土壤元素含量的影响

在草原生态系统中,土壤是植物生长发育最重要的基质,对植物群落动态有显著的影响。刈割是内蒙古典型草原区除放牧外最重要的利用方式。研究不同刈割频度对典型草原区群落特征和若干土壤性质的影响及土壤因子与群落特征的相关性,旨在得出对群落多样性最有利并最适宜生产利用的刈割频度。研究区设置在内蒙古锡林浩特市东部以大针茅建群的典型草原;在2009—2013年进行不同频度的刈割处理,共设置处理,一年两次刈割、一年一次刈割、两年一次(割一年休一年)刈割、围封,在2013年8月采集测定土壤养分的样品。刈割对群落多样性影响显著,割一年休一年Shannon-Wiener多样性指数、Pielou均匀度指数、丰富度指数均高于其他刈割处理(P0.05);不同频度刈割下,一年两次刈割处理下土壤20—30cm和30—40cm的有机质含量显著高于其他处理(P0.05);不同频度刈割处理下土壤中的速效磷和速效氮的含量没有显著差异;一年两次处理的土壤全氮含量显著高于其他处理(P0.05)。Shannon-Wiener多样性指数与有机质含量、全氮含量呈显著负相关;Pielou均匀度指数与土壤元素间无显著相关关系;Richness指数与有机质含量呈显著负相关,与全氮含量为极显著负相关关系。割一年休一年刈割处理下土壤元素含量呈现更好的状态,结合群落物种多样性及生产利用的角度,割一年休一年为最合理的刈割频度。     

Severed stems of Amaranthus palmeri are capable of regrowth and seed production in Gossypium hirsutum

Field studies were conducted to evaluate the capacity of Amaranthus palmeri to grow and reproduce following incomplete physical control in Gossypium hirsutum fields. A. palmeri plants that emerged simultaneously with a G. hirsutum crop were selected for use. Treatments included severing the main stem of flowering plants at heights of 0, 3 and 15 cm above the soil level. A non‐cut/intact control, in which the apical meristem was not removed, was also included. Six weeks after treatment, intact A. palmeri plants had grown to a mean height of 210 cm (SE = 38) and produced 477 408 (SE = 81 250) seeds per plant. Thirty‐five percent of the A. palmeri plants cut back to a height of 15 cm above the soil level did not recover from the treatment; survivors regrew to a mean height of 102 cm (51% reduction, compared to intact plants) and produced 116 000 seeds per plant (73% reduction). A. palmeri plants cut to 3 cm above the soil level had a mortality rate of 64%, an 82% reduction in final plant height, and produced 28 000 seeds per plant. When stems were severed at the soil surface, plant mortality was 95%; final plant height and seed production of survivors were reduced by 95 and 99%, respectively, relative to the control. G. hirsutum seeded yields exceeded 3 t ha^?1 when A. palmeri plants were cut back to at least 15 cm, whereas yield was reduced 50% in the control treatment, where A. palmeri growth was not interrupted by cutting. In conclusion, while there is immediate benefit of removing A. palmeri plants in terms of G. hirsutum yield, incomplete stem removal can have multi‐season implications. Results demonstrate that severely pruned A. palmeri plants can resume growth, reach reproductive maturity and produce viable seed, which have the potential to repopulate soil seedbanks.     

The effect of varying alkaloid concentrations on the feeding behavior of gypsy moth larvae, Lymantria dispar (L.) (Lepidoptera: Lymantriidae)

Nine alkaloids (acridine, aristolochic acid, atropine, berberine, caffeine, nicotine, scopolamine, sparteine, and strychnine) were evaluated as feeding deterrents for gypsy moth larvae (Lymantria dispar (L.); Lepidoptera: Lymantriidae). Our aim was to determine and compare the taste threshold concentrations, as well as the ED₅₀ values, of the nine alkaloids to determine their potency as feeding deterrents. The alkaloids were applied to disks cut from red oak leaves (Quercus rubra) (L.), a plant species highly favored by larvae of this polyphagous insect species. We used two-choice feeding bioassays to test a broad range of biologically relevant alkaloid concentrations spanning five logarithmic steps. We observed increasing feeding deterrent responses for all the alkaloids tested and found that the alkaloids tested exhibited different deterrency threshold concentrations ranging from 0.1 to 10 mM. In conclusion, it appears that this generalist insect species bears a relatively high sensitivity to these alkaloids, which confirms behavioral observations that it avoids foliage containing alkaloids. Berberine and aristolochic acid were found to have the lowest ED₅₀ values and were the most potent antifeedants. Handling Editor: Joseph Dickens.     

Yield components of sesame (sesamum indicum L.) under different population densities

The objective of this investigation was to study (a) the yield components of sesame under different population densities and (b) their association with seed yield per unit area. The branched, non-shattering variety “Baco” was used. Rows were 60 cm apart and spacing between plants on the row was 2.5, 7.5, 15.0, 22.5, or 30.0 cm. Plant height and height of first fruit were only slightly affected by changes in plant density. More branches were produced at lower densities. Capsule length was smaller and number of seeds was lower only at the 2.5 cm spacing. Number of capsules and seed yield per plant increased in wider spacings. Number of capsules and seed yield per unit area decreased at spacings wider than 7.5 cm. Yield of seed per unit area was positively and significantly correlated with plant height, number of primary branches, number of capsules per plant, number of seeds per capsule, seed weight, seed yield per plant and number of capsules per unit area.     

Production of tropane alkaloids by transformed root cultures of Atropa belladonna in stirred bioreactors with a stainless steel net

A scale up of transformed root cultures of Atropa belladonna from a 300-ml flask to a 30-l tank was accomplished without any reduction in alkaloid productivity. Cutting treatment of seed cultures showed no distinct effect on root growth, morphology, and alkaloid content in conical flasks during 1 month of culture. Randomly cut roots thus grown were further cultivated in 3-l and 30-l modified stirred bioreactors for a scale-up culture. After 1 month of culture, 1490 mg of tropane alkaloids was produced by a 30-l culture of A. belladonna transformed roots. These roots contained the same level of atropine (5.4 mg/ g dw) as the roots of this plant grown in the field for 12 months and still contained a considerable amount of other alkaloids including 1.6 mg/g dw of 6-β-hydroxyhyoscyamine, 0.9 mg/g dw of scopolamine, and 2.0 mg/g dw of littorine. Received: 12 June 1998 / Revision received: 31 August 1998 / Accepted: 27 October 1998     

Developmental regulation of benzylisoquinoline alkaloid biosynthesis in opium poppy plants and tissue cultures

Summary Opium poppy (Papaver somniferum L.) contains a number of pharmaceutically important alkaloids of the benzylisoquinoline type including morphine, codeine, papaverine, and sanguinarine. Although these alkaloids accumulate to high concentrations in various organs of the intact plant, only the phytoalexin sanguinarine has been found at significant levels in opium poppy cell cultures. Moreover, even sanguinarine biosynthesis is not constitutive in poppy cell suspension cultures, but is typically induced only after treatment with a funga-derived elicitor. The absence of appreciable quantities of alkaloids in dedifferentiated opium poppy cell cultures suggests that benzylisoquinoline alkaloid biosynthesis is developmentally regulated and requires the differentiation of specific tissues. In the 40 yr since opium poppy tissues were first culturedin vitro, a number of reports on the redifferentiation of roots and buds from callus have appeared. A requirement for the presence of specialized laticifer cells has been suggested before certain alkaloids, such as morphine and codeine, can accumulate. Laticifers represent a complex internal secretory system in about 15 plant families and appear to have multiple evolutionary origins. Opium poppy laticifers differentiate from procambial cells and undergo articulation and anastomosis to form a continuous network of elements associated with the phloem throughout much of the intact plant. Latex is the combined cytoplasm of fused laticifer vessels, and contains numerous large alkaloid vesicles in which latex-associated poppy alkaloids are sequestered. The formation of alkaloid vesicles, the subcellular compartmentation of alkaloid biosynthesis, and the tissue-specific localization and control of these processes are important unresolved problems in plant cell biology. Alkaloid biosynthesis in opium poppy is an excellent model system to investigate the developmental regulation and cell biology of complex metabolic pathways, and the relationship between metabolic regulation and cell-type specific differentiation. In this review, we summarize the literature on the roles of cellular differentiation and plant development in alkaloid biosynthesis in opium poppy plants and tissue cultures.     

Implementation of functional genomics for gene discovery in alkaloid producing plants

Two centuries after the discovery of the first alkaloids, many enzymes involved in plant alkaloid biosynthesis have been identified. Nevertheless, the biosynthetic pathways for most of the plant alkaloids still remain incompletely characterised and understanding the regulatory mechanisms controlling the onset and flux of alkaloid biosynthesis is virtually inexistent. This information is however crucial to allow modelling of metabolic networks and predictive metabolic engineering. In the postgenomics era, new functional genomics tools, enabling comprehensive investigations of biological systems, are continuously emerging and are now gradually being implemented in the field of plant secondary metabolism as well. Here we discuss the advances these promising new technologies have already brought and may still bring with regard to the dissection of plant alkaloid biosynthesis. Encouraging results were obtained in alkaloid producing species such as Papaver somniferum, Catharanthus roseus and Nicotiana tabacum. Therefore we anticipate that functional genomics and the knowledge it brings along, will eventually allow a better exploitation of the plant biosynthetic machinery.