Silvia R. Leicach

Post-damage alkaloid concentration in sweet and bitter lupin varieties and its effect on subsequent herbivory

Abstract:  While most lupin species possess quinolizidine alkaloids, sweet (low alkaloid) varieties are more palatable but at the same time more susceptible to herbivory. Nevertheless, as they are not totally devoid of alkaloids, it may be possible that their alkaloid levels increase after damage. The aim of this study was to compare inductive responses to herbivory in sweet and bitter varieties of Lupinus albus (L.) and Lupinus angustifolius (L.), and to assess if these responses were effective to stop subsequent herbivory. Two experiments were carried out; in the first, Anticarsia gemmatalis (Hübner; Lep., Noctuidae) caterpillars were introduced in field‐growing lupin plants and allowed to feed for 72 h, after which leaves were collected and analysed for alkaloid content and composition. The second experiment was a bioassay, in which leaves collected from experiment 1, from treated and control plants, were offered to another set of Anticarsia caterpillars, and consumption was recorded after 24 h. We found that both L. albus varieties (sweet and bitter) had an increase in their alkaloid concentration after damage, while none of the L. angustifolius varieties had. The sweet L. albus variety, Rumbo, had a greater inductive response than the bitter variety. When leaves were offered to caterpillars (bioassay), this variety showed the greatest difference between consumption of controls and previously eaten leaves, implying that alkaloid levels reached after damage were effective to deter subsequent herbivores as a result of plants probably overcoming a ‘palatability threshold’.

Constituents of the root exudate of Avena fatua grown under far-infrared-enriched light.

The constituents of the root exudate of plantlets of wild oats (Avena fatua) grown in the greenhouse under far-IR-enriched radiation were analysed for the first time by HPTLC and capillary GC, and further separated by medium-pressure liquid chromatography (MPLC; monitored by TLC) and characterised by GC-EIMS and 1H-NMR. This combination of methodologies permitted the study of root exudates under controlled conditions and is appropriate for examining a variety of ecophysiological/environmental effects in a short time period. In this instance, the response compounds of the irradiated plantlets were identified as linear and branched alcohols, linear and branched alkanes, a bicyclic monoterpene, mono- and bicyclic sesquiterpenes, and free and esterified fatty acids. An ester, isopropyl myristate, was the main component present, although the unusual occurrence of branched compounds, sesquiterpenoids and related compounds of isoprenoid metabolism is noteworthy. The effect of far-IR-enriched light on the production of these compounds is discussed. Copyright

Changes in Eucalyptus camaldulensis essential oil composition as response to drought preconditioning

Abstract Water deficit, a common constraint in forestry, is the main cause of plant stress during plantation. The survival and growth of seedlings is also compromised by herbivory during establishment. The potential of nursery preconditioning to enhance survival chances of future trees by reducing palatability or attracting beneficial insects as a result of changes in chemical defences may be an answer to overcome this situation. Changes in essential oil production and composition were evaluated by GC and GC-MS in Eucalytus camaldulensis seedlings submitted to drought during four weeks at the last stage of nursery period (20 weeks). Significant changes in essential oil relative composition were found. Seedlings (young leaves) submitted to drought developed a terpenoid blend, which has been previously associated to mature leaves and related to their higher resistance towards herbivory. Total amount of non-oxygenated terpenes decreased by 44%, whereas some oxygenated sesquiterpenes (globulol, epiglobulol and ledol) were doubled, and 1,8-cineole content was enhanced by 28.3%.

Changes in Lupinus albus and Lupinus angustifolius Alkaloid Profiles in Response to Mechanical Damage

The aim of this work was to evaluate chemical responses to biomass removal mimicking large herbivore action in Lupinus albus and Lupinus angustifolius aerial parts. GC and GC-MS were used to determine total alkaloid content (TAC) and alkaloid relative abundances in bitter and sweet varieties of each species. Bitter genotypes Vila vehla (Vv; 3.95 +/- 0.26 mg/g of DM) and El Harrach (EH; 3.99 +/- 0.19 mg/g of DM) showed after damage 22 and 32.8% TAC increases, respectively. Even sweet varieties, with very low alkaloid contents, Gungurru (Gu; 0.51 +/- 0.09 mg/g of DM) and Rumbo (Ru; 0.53 +/- 0.09 mg/g of DM) exhibited higher induced responses of 58.8 and 67.9%, respectively, and their final TAC values remained low, distinctly apart from those corresponding to bitter species. Moreover, minor components such as ammodendrine, reported to exhibit teratogenic potential, showed no significant changes in their relative abundances in response to biomass removal in these genotypes.

Genistin and quinolizidine alkaloid induction in L. angustifolius aerial parts in response to mechanical damage

Lupinus species are commonly used as annual forage and for grain production. They are considered alternative crops to soybean due to their adaptation to cool environments and dry soils. The present study is an analysis of the chemical changes coming from biomass removal in a sweet genotype of Lupinus angustifolius. Mechanical damage induced significant increases in antioxidant activity (12.4%), as well as in flavonoid and phenolic content (36.6% and 12.0%, respectively). This sweet lupin also exhibited a higher induced response (68.2%) in the alkaloid content after the damage. These same alkaloids were identified in the control samples and all of them, except lupanine, showed higher relative abundances in response to mechanical damage. Traces of α-isolupanine were detected in control samples and showed a 23.5-fold increase in response to biomass removal. Mechanical damage also produced a striking increase (8.6-fold) in relative abundance of genistin.

Changes in Senecio grisebachii pyrrolizidine alkaloids abundances and profiles as response to soil quality.

Abstract Senecio grisebachii Baker is an invasive weed considered to be toxic due to the presence of pyrrolizidine alkaloids (PA) in its tissues. The PA production by S. grisebachii aerial parts was evaluated in samples grown in two Argentinean Rolling Pampa fields with the same kind of soil but differing in the length of their exploitation period by conventional tillage practices and, consequently, in their deterioration level. We found significant differences in the relative concentrations of seven alkaloids between samples taken from the two fields. Seneciphylline was the most abundant alkaloid in inflorescences from less deteriorated soil (LD) while senecionine was the major one in those from highly deteriorated soil (D) being followed by seneciphylline, integerrimine, and minor amounts of spartiodine, jacobine, jacozine and retrorsine. A significant increase in total alkaloid content (TAC) was observed in inflorescences from samples growing in D soil (3.52±0.20 mg/g DW) when comparing with those from samples grown in LD one (3.23±0.26).

Nonpolar lipid composition of Chenopodium album grown in continuously cultivated and nondisturbed soils

Chenopodium album L. plants grown in continuously cultivated and in nondisturbed soils were compared in terms of the compositions of nonpolar extracts of the corresponding aerial parts. Both light petroleum ether extracts of C. album L. were analyzed by high-performance thin-layer LC, capillary GC, and capillary GC-El-MS. Further percolation and medium-pressure LC, along with EI-MS analysis, permitted the separation and identification of the chemical constituents. Differences were observed between mean contents of the chemical constituents of C. album L., with respect to nonpolar extracts, obtained from continuously cultivated and from nondisturbed soils, in particular in linear and branched long-chain hydrocarbons, FA and their esters, and long-chain linear alcohols and aldehydes. The most remarkable features of the disturbed soils were a pronounced increase in the amounts of linear hydrocarbons and a decrease in the relative proportions of FA.

Host selection, oviposition behaviour and leaf traits in a specialist willow sawfly on species of Salix (Salicaceae)

Plant genotype influences plant–herbivore interactions by affecting insect attraction, acceptance and development. Here we linked oviposition behaviour of the specialist willow sawfly Nematus oligospilus Förster (Hymenoptera: Tenthredinidae) with leaf traits on different Salix L. (Salicaceae) genotypes. This was done as a first step to find oviposition cues that guide females to their host plants. By means of choice and no‐choice bioassays we analysed host selection according to willow genotype and leaf surface. We also studied larval performance, adult fecundity and effect of experience on host selection. Nematus oligospilus prefers to oviposit on S. nigra. The least preferred genotype, S. viminalis, showed better larval performance and highest adult fecundity. Host preference was not modified by larval feeding experience. By means of light and scanning electron microscopy we described ovipositor and leaf micromorphology. The egg is laid inside the epidermis or between the epidermis and adjacent chlorenchyma, showing a tight association with the leaf. Leaf toughness was lowest for S. nigra and higher for S. viminalis and S. babylonica. Total nitrogen and protein content were higher on S. viminalis and S. babylonica. Total phenolics and phenolic glycosides were the highest and more diverse on S. nigra. Salicin content levels correlate with oviposition preference, suggesting the role of salicylates as oviposition stimulants. Results suggest that oviposition preference on S. nigra may be related to lower leaf toughness and ease of injection of female saw‐like ovipositor, and motivated by the presence of phenolic glycosides. Nitrogen levels may explain better larval performance and adult fecundity in S. viminalis. Thus, a balance among the different leaf traits determines the outcomes observed in this study.

Plant Secondary Metabolites: Structure–Activity Relationships in Human Health Prevention and Treatment of Common Diseases

Abstract Mankind has used plants for different purposes, such as disease prevention and treatment, among them. Ancient folk medicine has taken advantage of some of their effects against insect attack, parasitic, bacterial, viral, and fungal infections, and also of anti-inflammatory, analgesic, and/or antipyretic properties of some of their components. Moreover, bioactive natural products have been early used in agriculture to protect crops from pests and are revised nowadays to contribute in integrated pest management in order to improve agroecosystems sustainability and quality of crop-derived foodstuff directly affecting human health (nutraceuticals, toxins). Plant secondary metabolites have been the source of lead molecules in drug development because of their permanently growing diversity and their high level of specificity in biological activities, some of them being able to act in additive or synergistic ways. In combination with one another, structurally different plant-derived products may increase their efficacy and/or have a broader spectrum of activity. Current concerns about deleterious effects of synthetic chemicals used for medical purposes have encouraged a worldwide research work on natural products and derived structures potentially useful in the development of alternative treatments for most common illnesses associated with aging process. Phenolic derivatives, flavonoids, and isoflavones have been proved to play preventive roles against degenerative diseases triggered by free radical action, having potential to diminish intake of some dangerous synthetic antioxidants. It has been demonstrated for most secondary metabolite families that small changes in the basic representative structure may result in significant qualitative and quantitative changes in their biological activity. Among those families, phenolics, flavonoids, terpenoids, and nitrogen and sulfur derivatives are currently tested to prevent and/or treat a wide spectrum of human diseases. The aim of this review is the analysis of structure–activity relationships in most common plant secondary metabolite families known to contribute to human health prevention, including those involved in the treatment of neurological degenerative diseases, cancer, parasitic infections, and blood vessel diseases.

Chemical Defenses in Eucalyptus Species: A Sustainable Strategy Based on Antique Knowledge to Diminish Agrochemical Dependency

A large number of tree species from different genera have being used world over for their timber resources. Most of them produce roundwood for sawmill and commercial valuable derivatives such as those related to pulp and paper, hardboard and particleboard industries (FAO 2011b). Species within Fabaceae, Pinaceae, Myrtaceae, Cupressaceae, Araucariaceae, Meliaceae, Fagaceae, and Proteaceae families are exploited by those industries.