Atividade alelopática dos lixiviados de Asemeia extraaxillaris (Polygalaceae) sobre o crescimento de Ipomoea cordifolia / Allelopathic activity of leachates from Asemeia extraaxillaris (Polygalaceae) on the growth of Ipomoea cordifolia

RESUMO O objetivo desse trabalho foi avaliar a atividade alelopática dos lixiviados das raízes e folhas secas de Asemeia extraaxillaris sobre o crescimento de corda de viola Ipomoea cordifolia em casa de vegetação, para avaliação dos efeitos sobre o estresse oxidativo. Nos bioensaios foram utilizadas três concentrações (0,25 - 5,00 e 10,00 g) e um controle, com quatro repetições de 10 plantas, cultivadas em solo durante 30 dias. Os lixiviados possuem ação alelopática e o maior efeito foi verificado para o pó das raizes. O efeito inibitório foi dose-dependente e o aumento do estresse oxidativo foi observado pelos níveis da catalase, peroxidase, superóxido dismutase, glutationa redutase, peroxidação lipídica e síntese de formazan. Concluiu-se que A. extraaxillaris possui substâncias capazes de afetar a emergência, o crescimento e o estresse oxidativo de I. cordifolia.

ABSTRACT The purpose of this article is to assess the allelopathic activity of leachates from the roots and dried leaves of Asemeia extraaxillaris on the germination and growth of corda de viola (Ipomoea cordifolia) in a greenhouse, and evaluate its effect on oxidative stress. For the bioassays, three concentrations (0.25, 5.00, and 10.00 g) and one control were used, with four replications of 10 plants, cultivated in soil for 30 days. The leachates exhibited allelopathic action, and the greatest effect was found in the root powder. The inhibitory effect was dose-dependent and the increase in oxidative stress was observed by the levels of catalase, peroxidase, superoxide dismutase, glutathione reductase, lipid peroxidation, and formazan synthesis. It was affirmed that A. extraaxillaris contains substances capable of affecting seedling emergence, growth, and oxidative stress in I. cordifolia.

Evolution of mycoheterotrophy in Polygalaceae: The case of Epirixanthes.

PREMISE OF THE STUDY: The mycoheterotrophic lifestyle has enabled some plant lineages to obtain carbon from their mycorrhizal symbionts. The mycoheterotrophic genus Epirixanthes (Polygalaceae) consists of six species from tropical Asia. Although it is probably closely related to the chlorophyllous genus Salomonia and linked to arbuscular mycorrhizal fungi, lack of DNA sequence data has thus far prevented these hypotheses from being tested. Therefore, the evolutionary history of Epirixanthes remains largely unknown. METHODS: We reconstructed the phylogenetic relationships of Epirixanthes based on nuclear ITS and plastid matK data. Divergence times were inferred using a Bayesian relaxed clock approach, and we phylogenetically analyzed its mycorrhizal symbionts. We furthermore assigned these symbionts to operational taxonomic units, compared them with symbionts of other Polygalaceae, and measured their phylogenetic diversity. KEY RESULTS: We found that Epirixanthes is placed in tribe Polygaleae as sister to Salomonia. Epirixanthes has a Miocene-Oligocene stem age and grows exclusively in symbiosis with fungi of Glomeraceae. Salomonia and some Polygala species are linked to both Glomeraceae and Acaulosporaceae, resulting in higher phylogenetic diversity values. The majority of the symbionts of Epirixanthes are not found in Salomonia or Polygala, although a few shared fungal taxa are found. CONCLUSIONS: Epirixanthes forms a relatively young mycoheterotrophic lineage. The Oligocene-Miocene origin suggests its evolution was influenced by the environmental dynamics in Southeast Asia during this time. Although comparison of fungi from Epirixanthes with those from Salomonia and Polygala suggests some specialization, many other mycoheterotrophic plants are linked to a more narrow set of Glomeraceae.

Floral morphology and development in Quillajaceae and Surianaceae (Fabales), the species-poor relatives of Leguminosae and Polygalaceae.

BACKGROUND AND AIMS: Molecular phylogenies have suggested a new circumscription for Fabales to include Leguminosae, Quillajaceae, Surianaceae and Polygalaceae. However, recent attempts to reconstruct the interfamilial relationships of the order have resulted in several alternative hypotheses, including a sister relationship between Quillajaceae and Surianaceae, the two species-poor families of Fabales. Here, floral morphology and ontogeny of these two families are investigated to explore evidence of a potential relationship between them. Floral traits are discussed with respect to early radiation in the order. METHODS: Floral buds of representatives of Quillajaceae and Surianaceae were dissected and observed using light microscopy and scanning electron microscopy. KEY RESULTS: Quillajaceae and Surianaceae possess some common traits, such as inflorescence morphology and perianth initiation, but development and organization of their reproductive whorls differ. In Quillaja, initiation of the diplostemonous androecium is unidirectional, overlapping with the petal primordia. In contrast, Suriana is obdiplostemonous, and floral organ initiation is simultaneous. Independent initiation of five carpels is common to both Quillaja and Suriana, but subsequent development differs; the antesepalous carpels of Quillaja become fused proximally and exhibit two rows of ovules, and in Suriana the gynoecium is apocarpous, gynobasic, with antepetalous biovulate carpels. CONCLUSIONS: Differences in the reproductive development and organization of Quillajaceae and Surianaceae cast doubt on their potential sister relationship. Instead, Quillaja resembles Leguminosae in some floral traits, a hypothesis not suggested by molecular-based phylogenies. Despite implicit associations of zygomorphy with species-rich clades and actinomorphy with species-poor families in Fabales, this correlation sometimes fails due to high variation in floral symmetry. Studies considering specific derived clades and reproductive biology could address more precise hypotheses of key innovation and differential diversification in the order.

Nota sobre a ocorrência de pétalas reduzidas em espécies de Polygala L. subgênero Hebeclada (Chodat) Blake (Polygalaceae) da Região Sul do Brasil / A note about the occurrence of reduced petals in species of Polygala L. subgenus Hebeclada (Chodat) Blake (Polygalaceae) from southern Brazil

O número de pétalas é um dos caracteres taxonômicos utilizados na circunscrição dos subgêneros de Polygala. Até o momento, a corola das espécies do subgênero Hebeclada era descrita apresentando apenas três pétalas, uma inferior e central, denominada carena e duas laterais superiores aderidas à bainha estaminal. Dentre os 12 subgêneros de Polygala, a ocorrência de corola trímera era registrada apenas nos subgêneros Polygala e Hebeclada. O presente trabalho trata da ocorrência inédita de corola pentâmera em espécies de Polygala do subgênero Hebeclada, apresentando fotografias e comentários adicionais sobre estas pétalas reduzidas, não referidas para o subgênero até o momento.

The number of petals in the flowers is a taxonomic character used in the circumscription of the subgenera of Polygala. Until now, the corolla of the species of subgenus Hebeclada was described having tree petals, one inferior and central called carina and two lateral adnated to the staminal sheath. Among the 12 subgenera of Polygala, the occurrence of trimerous corolla was only known in subgenera Polygala and Hebeclada. This paper presents the discovery of pentamerous corolla in species of Polygala subgenus Hebeclada, presenting photos and additional comments about this reduced petals unknown for the subgenus until this moment.

The role of biotic and abiotic factors in evolution of ant dispersal in the milkwort family (polygalaceae).

A phylogenetic approach was taken to investigate the evolutionary history of seed appendages in the plant family Polygalaceae (Fabales) and determine which factors might be associated with evolution of elaiosomes through comparisons to abiotic (climate) and biotic (ant species number and abundance) timelines. Molecular datasets from three plastid regions representing 160 species were used to reconstruct a phylogenetic tree of the order Fabales, focusing on Polygalaceae. Bayesian dating methods were used to estimate the age of the appearance of ant-dispersed elaiosomes in Polygalaceae, shown by likelihood optimizations to have a single origin in the family. Topology-based tests indicated a diversification rate shift associated with appearance of caruncular elaiosomes. We show that evolution of the caruncular elaiosome type currently associated with ant dispersal occurred 54.0-50.5 million year ago. This is long after an estimated increase in ant lineages in the Late Cretaceous based on molecular studies, but broadly concomitant with increasing global temperatures culminating in the Late Paleocene-Early Eocene thermal maxima. These results suggest that although most major ant clades were present when elaiosomes appeared, the environmental significance of elaiosomes may have been an important factor in success of elaiosome-bearing lineages. Ecological abundance of ants is perhaps more important than lineage numbers in determining significance of ant dispersal. Thus, our observation that elaiosomes predate increased ecological abundance of ants inferred from amber deposits could be indicative of an initial abiotic environmental function.

Diversification of a large genus in a continental biodiversity hotspot: temporal and spatial origin of Muraltia (Polygalaceae) in the Cape of South Africa.

Phylogenetic relationships in the largely South African genus Muraltia (Polygalaceae) are assessed based on DNA sequence data (nuclear ribosomal ITS, plastid atpB-rbcL spacer, trnL intron, and trnL-F spacer) for 73 of the 117 currently recognized species in the genus. The previously recognised subgenus Muraltia is monophyletic, but the South African endemic genus Nylandtia is embedded in Muraltia subgenus Psiloclada. Subgenus Muraltia is found to be sister to subgenus Psiloclada. Estimates show the beginning of diversification of the two subgenera in the early Miocene (Psiloclada, 19.3+/-3.4 Ma; Muraltia, 21.0+/-3.5 Ma) pre-dating the establishment of the Benguela current (intermittent in the middle to late Oligocene and markedly intensifying in the late Miocene), and summer-dry climate in the Cape region. However, the later increase in species numbers is contemporaneous with these climatic phenomena. Results of dispersal-vicariance analyses indicate that major clades in Muraltia diversified from the southwestern and northwestern Cape, where most of the species are found today.