Among the diversity of secondary metabolites which are produced by plants as means of defence against herbivores and microbes, pyrrolizidine alkaloids (PAs) are common in Boraginaceae, Asteraceae and some other plant families. Pyrrolizidine alkaloids are infamous as toxic compounds which can alkylate DNA und thus cause mutations and even cancer in herbivores and humans. Almost all genera of the family Boraginaceae synthesize and store this type of alkaloids. This review reports the available information on the present status (literature up to early 2014) of the pyrrolizidine alkaloids in the Boraginaceae and summarizes the topics structure, distribution, chemistry, chemotaxonomic significance, and biological properties.

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Diversity of Pyrrolizidine Alkaloids in the Boraginaceae Structures, Distribution, and Biological Properties

The Botany of the Guayana Highland--Part XI

A number of floristic and vegetation studies apply the terms campo rupestre, campo de altitude (or Brazilian paramo), and Tepui to neotropical azonal outcrop and montane vegetation. All of these are known to harbor considerable numbers of endemic plant species and to share several genera. In order to determine whether currently known combinations of vascular plant genera could help circumscribe and distinguish these vegetation types, we selected 25 floras which did not exclude herbs and compiled them into a single database. We then compared the Sorensen similarities of the genus–assemblages using the numbers of native species in the resulting 1945 genera by multivariate analysis. We found that the circumscription of campo rupestre and other Neotropical outcrop vegetation types may not rely exclusively on a combination of genera.

http://www.inot.org.br/artigo/2010_Campo_Rupestre_Pl_Ecol.pdf

Can campo rupestre vegetation be floristically delimited based on vascular plant genera

Pyrrolizidine alkaloids (PAs), mainly those with a 1,2-double bond in the necine base moiety (=1,2-dehydropyrrolizidines), constitute a class of well studied compounds with respect to their flux through different trophic levels. Plants belonging to various clades (e.g. Echiteae, Eupatorieae and Senecioneae, Boraginaceae, and Crotalarieae) biosynthesize PAs as N-oxides, generally in the roots, and transport them through the phloem to stems, leaves, and reproductive structures, where they act as potent deterrents against non-specialist herbivores. On the other hand, PA specialist herbivores (mainly arctiid moths, danaine and ithomiine butterflies, and some leaf beetles) have become able to overcome this chemical barrier, and to sequester these alkaloids from their larval host plants or from sources visited by adults, such as flowers and dead or withered plants. Specialists use PAs for their own benefit as chemical defence against a vast array of predators (e.g. ants, lacewings, spiders, lizards, birds, and mammals), but some predators are able to feed on PA-insects, by avoiding or physiologically overcoming PAs present in tissues of the ingested prey. Parasitoids may be affected by PAs, depending on their degree of specialization in relation to PA-insects. Arctiidae, Danainae and Ithomiinae also use PAs as precursors of sexual pheromones. The effects of PAs on trophic interactions have been intensely studied over the last four decades, but some open questions remain, and are discussed, such as the underlying mechanisms that lead to PA diversification, activity of different PA structures, synergism among PAs and other so-called defensive substances in PA-plants, and the ability to overcome this chemical barrier by predators and parasitoids.

Effects of pyrrolizidine alkaloids through different trophic levels

Plant parasitic nematodes cause significant crop damage globally. Currently, many nematicides have been banned or are being phased out in Europe and other parts of the world because of environmental and human health concerns. Therefore, we need to focus on sustainable and alternative methods of nematode control to protect crops. Plant roots contain and release a wide range of bioactive secondary metabolites, many of which are known defense compounds. Hence, profound understanding of the root mediated interactions between plants and plant parasitic nematodes may contribute to efficient control and management of pest nematodes. In this review, we have compiled literature that documents effects of root metabolites on plant parasitic nematodes. These chemical compounds act as either nematode attractants, repellents, hatching stimulants or inhibitors. We have summarized the few studies that describe how root metabolites regulate the expression of nematode genes. As non-herbivorous nematodes contribute to decomposition, nutrient mineralization, microbial community structuring and control of herbivorous insect larvae, we also review the impact of plant metabolites on these non-target organisms.

Impacts of Root Metabolites on Soil Nematodes.

Pyrrolizidine alkaloid profiles in Crotalaria species from Brazil: chemotaxonomic significance.

Este trabalho apresenta o estudo taxonomico do genero Senna para o Rio Grande do Sul, Brasil. Sao encontradas 19 especies, sendo que Senna aphylla (Cav.) H.S. Irwin & Barneby, S. araucarietorum H.S. Irwin & Barneby, S. pendula (Willd.) H.S. Irwin & Barneby, S. scabriuscula (Vogel) H.S. Irwin & Barneby e S. spectabilis (DC.) H.S. Irwin & Barneby sao registradas pela primeira vez para a flora do Estado. Sao apresentadas chave analitica, descricoes e ilustracoes para as especies. Alem disso, sao fornecidos dados sobre a distribuicao geografica, habitat, nomes vulgares e importância economica das especies estudadas.

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O gênero Senna (Leguminosae, Caesalpinioideae) no Rio Grande do Sul, Brasil

Leguminosae is the most diverse family in the savannas of Roraima, which are the largest savanna areas in the Brazilian Amazon. This paper presents a floristic survey and an analysis of the geographic distribution patterns of Leguminosae taxa in a savanna area at Boa Vista, Roraima (02o52´07´´N; 60o43´03´´W). The survey identified 80 taxa belonging to 38 genera. Six taxa are new records for the flora of Roraima. The best-represented genera were Aeschynomene and Chamaecrista, both with seven species each. Leguminosae-Papilionoideae was the most diverse subfamily based on the number of genera (24) and infrageneric taxa (53). The phytogeographical analysis revealed predominance of taxa with a Neotropical distribution. The savanna site analyzed represents a legume diverse area, because it concentrates 87% of legume diversity referred for the savannas of Roraima.

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Diversidade de Leguminosae em uma área de savana do estado de Roraima, Brasil

Chromosome numbers in Brazilian species of Crotalaria (Leguminosae, Papilionoideae) and their taxonomic significance

Sao discutidos aspectos fitogeograficos de Crotalaria L. (Leguminosae) na Regiao Sul do Brasil. O genero possui distribuicao pantropical, sendo que no sul do Brasil apresenta nove especies nativas e sete introduzidas. As especies nativas de Crotalaria ocorrem nas provincias biogeograficas Paranaense, Atlântica e Pampeana. A distribuicao geografica das especies do genero ao longo dos tres Estados da regiao mostra um gradiente latitudinal de diversidade floristica decrescente do Parana para o Rio Grande do Sul. A regiao no Parana compreendida entre 49o50o W e 24o-26o S e a que apresenta a maior diversidade de especies.

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Andréia Silva Flores

Papers

Pyrrolizidine alkaloid profiles in Crotalaria species from Brazil: chemotaxonomic significance.

O gênero Senna (Leguminosae, Caesalpinioideae) no Rio Grande do Sul, Brasil

Diversidade de Leguminosae em uma área de savana do estado de Roraima, Brasil

Chromosome numbers in Brazilian species of Crotalaria (Leguminosae, Papilionoideae) and their taxonomic significance

Aspectos fitogeograficos das especies de Crotalaria L. (Leguminosae, Faboideae) na Regiao Sul do Brasil