Deposition of litter and nutrients in leaves and twigs in different plant communities of northeastern Mexico

Studies on litterfall and decomposition provide estimations of decomposition rates of different ecosystems.This is key information to understanding ecosystem dynamics and changes in a scenario of global warming.The objective of this research was to assess litterfall production,the potential deposition of macro and micronutrients through leaf and twig fall as well as macronutrient—use efficiency in three forest ecosystems at different altitudes： a pine forest mixed with deciduous species（S1）; a Quercus spp.forest（S2）; and,a Tamaulipan thornscrub forest（S3）.Total annual litterfall deposition was 594,742 and 533 g m^（-2） for S1,S2 and S3.Leaf litter was higher （68%） than twigs（18%）,reproductive structures（8%） or miscellaneous material（6%）.Micronutrient leaf deposition was higher for Fe followed by Mn,Zn and Cu.Macronutrient leaf deposition was higher for Ca followed by K,Mg and P.Even though P deposition in leaves and twigs was lower than other macronutrients,its nutrient use efficiency was higher than Ca,Mg or K.Altitude and species composition determine litter and nutrient deposition,with higher values at mid-altitudes（550 m）.Altitude is an important factor to consider when analyzing litter production as well as nutrient deposition as shown in this study.Litter production and nutrient deposition are expected to change in a scenario of global warming.

Hidden in plain sight:Morphological and phylogenetic evidence for Bouteloua arizonica,a species distinct from Bouteloua aristidoides(Poaceae,Chloridoideae)

Two varieties of Bouteloua aristidoides have been recognized,the widespread var.aristidoides and the more narrowly distributed var.arizonica.The two varieties differ in inflorescence form even more than that seen between many other closely related species of Bouteloua.We therefore asked whether these taxa might be better regarded as distinct species.A total of 93 vouchers were studied by using morphometry(principal components analysis and statistical tests),leaf micromorphology,ancestral state reconstruction,and/or molecular(ITS,trnC-rpoB and trnT-L-F)phylogenetic analyses.Except from the ITS tree,all results supported elevation of B.aristidoides var.arizonica to the rank of species,thus the new combination Bouteloua arizonica(M.E.Jones)L.F.Cuellar&Columbus comb.nov.et stat.nov.,is proposed.Chloroplast and combined chloroplast-nuclear molecular trees depicted var.arizonica as monophyletic(even in sympatric populations with var.aristidoides)and reveals phylogenetic structure within var.aristidoides for which the presence of new undescribed varieties of B.aristidoides(different from B.arizonica)is addressed.B.arizonica differs from B.aristidoides in having fewer branches per inflorescence,a bigger branch with more spikelets,and a shorter branch extension.Scanning electron microscopy revealed the presence of papillae on leaves of B.arizonica as a clear synapomorphy.Growing mature plants of B.arizonica from seeds in a greenhouse revealed a strong cleistogamous nature for this species for which gene flow in sympatric populations with B.aristidoides seems unlikely.A taxonomic treatment and distribution map for identification of B.arizonica is provided.

Induction of Defensive Responses in <i>Eucalyptus globulus</i>(Labill) Plants, against <i>Ctenarytaina eucalypti</i>(Maskell) (Hemiptera: Psyllidae)

This study evaluated the expression of defense compounds from the secondary metabolism of Eucalyptus globulus plants, subjected to direct and indirect stimuli by the insect Ctenarytaina eucalypti (blue gum Psyllid). Results showed that defense responses were activated in plants in all tested cases. Were detected and identified thirty-two compounds in the leaves of treated plants, of which five compounds differed with the control, and all are part of the chemical defenses from the plants, three of them were oxygenated monoterpenes (borneol, exo-2-hydroxy cineole and thymol), a aromatic carboxylic acid (benzoic acid) and a quinone (6-acethyl-flaviolin). The plants induced by volatile compounds and by indirect entomological manner, showed its capability to synthesize defensive compounds without a wound that promotes these responses. Were also found some constitutive secondary metabolites over expressed in the different inductions compared with the control.

In Vitro Evaluation of the Potential Antioxidant of Bidens segetum Mart. ex Colla (Asteraceae) in Melanocyte and Melanoma Cells

Bidens segetum Martius ex Colla known as the “pic&atilde;o do mato”, is an herbaceous plant that occurs in the Cerrado biome of some Brazilian states. Among the species of Bidens, we highlight B. pilosa known as “pic&atilde;o preto”, of which several activities are reported as antioxidant and antibacterial. Ethanolic extract from Bidens segetum (EEBs) showed an-tioxidant potential when analyzed by free radical 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay and antifungal activity against Cladosporium cladosporiodes and C. sphareospermum fungi. PFFR3.3 subfraction from EEBs has 81.5% of 5-O caffeoylquinic acid (5-CQA) and potential antioxidant (DPPH). However, PFFR3.3 did not decrease superoxide anion in metastatic melanoma cells by dihydroeth-idium assay (DHE). PP4 subfraction is a mixture of polyacetylenes that has antifungal (Cladosporium) and antioxidant activity, since reduced superoxide anion amount in melanoma cells after 5 min of treatment. However, no dose-response and time-response curve were observed, not even with the authentic standard (5-CQA). Complementary chemical studies will be performed to confirm the polyacetylenes and 5-CQA structures present in the EEBs from B. segetum and new methodologies should be performed to confirm the antioxidant activity of these com-pounds and the effects on melanocytes and melanomas.

Review of plant biogeographic studies in Brazil

Molecular phylogenetic studies have become a major area of interest in plant systematics, and their impacts on historical biogeographic hypotheses are not to be disregarded. In Brazil, most historical biogeographic studies have relied on animal phylogenies, whereas plant biogeographic studies have largely lacked a phylogenetic component, having a limited utility for historical biogeography. That country, however, is of great importance for most biogeographic studies of lowland tropical South America, and it includes areas from a number of biogeographic regions of the continent. Important biogeographic reports have been published as part of phylogenetic studies, taxonomic monographs, and regional accounts for small areas or phytogeographic domains, but the available information is subsequently scattered and sometimes hard to find. In this paper we review some relevant angiosperm biogeographic studies in Brazil. Initially we briefly discuss the importance of other continents as source areas for the South American flora. Then we present a subdivision of Brazil into phytogeographic domains, and we cite studies that have explored the detection of biogeographic units （areas of endemism） and how they are historically related among those domains. Examples of plant taxa that could be used to test some biogeographic hypotheses are provided throughout, as well as taxa that exemplify several patterns of endemism and disjunction in the Brazilian angiosperm flora.

Responses of the Host Plant Tissues to Gall Induction in Aspidosperma spruceanum Müell.Arg.(Apocynaceae)

The ontogenetic characterization of the leaf galls induced in the internervural region and in the second and third order veins of A. spruceanum Müell Arg. (Apocynaceae) aims to evaluate the distinct levels of cell reaction during the process of gall formation, and the relation between external gall morphology and the oviposition sites. The ground system had the most remarkable alterations, namely, the non differentiation of palisade parenchyma in both leaf sides, the hyperplasia of the spongy parenchyma and the neoformation of fibersclereids, a cell type not observed in non galled leaves. Changes of the feeding sites inside the larval chamber reveal distinct levels of cell competence to respond to the insects stimuli and explain the variations in the shape of the larval chamber.

Tree structure and diversity of lowland Atlantic forest fragments：comparison of disturbed and undisturbed remnants

This study describes the tree community structure of three moist lowland Atlantic Forest fragments in Rio de Janeiro State, southeastern Brazil. Two fragments were disturbed and an undisturbed one was used as reference. Our hypothesis was that disturbed fragments show distinct structural patterns in comparison with undisturbed stands due to past disturbance practices and forest fragmentation. Four 100 ×5 m sampling plots were demarcated in each fragment and all live and dead trees with DBH C 5 cm were located, measured and identified. The results supported our hypothesis, due to the high values found for standing dead trees, an increase of dominance of a few pioneer species, lower values of large trees and species richness in disturbed fragments in comparison with the undisturbed one. The advanced fragmentation process in the Southern Brazilian lowland areas and the high species richness in undisturbed areas highlight these forest fragments as priority areas for conservation and management.

Free amino acid content in trunk,branches and branchlets of Araucaria angustifolia(Araucariaceae)

Araucaria angustifolia(Bertol.) O. Kuntze exhibits dimorphism in its stem structure, where the trunk is orthotropic and branches and branchlets(primary and secondary branches) are plagiotropic. These stems exhibit different behavior when used for vegetative propagation,and only segments of trunk can form a complete plant. The physiological and biochemical mechanisms that characterize these stems are still little known. The aim of this study was to describe the free amino acid profiles in trunks,branches, and branchlets of A. angustifolia. Segments of 5 cm in length were excised from young individuals below the stem apex. The needles were removed and samples were frozen and lyophilized. The determinations were made by high-performance liquid chromatography, and the results were expressed as lg/g fresh weight(FW). The trunks and branches had the highest content of total amino acids, which were 112.23 ± 20.57 lg/g FW and 111.97 ± 27.78 lg/g FW, respectively. The amino acids—glutamine, aspartate and c-aminobutyric acid and tyrosine—were noticeably higher in the three types of stems.In the trunk, a higher amount of asparagine and tryptophan,was also detected. Glutamic acid and glutamine were found in higher quantities in the branches. The branchlets had very low total amino acid content (30.79 ± 4.19 lg/g FW), wherein asparagine is the only amino acid not detected. Thus, it was observed that the profile of the free amino acid differs among trunks, branches, and branchlets in A. angustifolia, indicating that they perform different functions.

Morphological Patterns of a Hymenopteran Gall on the Leaflets of Caryocar brasiliense Camb.(Caryocaraceae)

Anatomical studies in the leaflet globoid galls of Caryocar brasiliense, the “pequi”, aimed to answer how oviposition and the feeding behavior of the galling herbivores altered the morphogenical patterns of the host plant. C. brasiliense globoid gall was 1.28 ± 0.20 mm × 0.90 ± 0.25 mm, with hairy surface;it is sessile and projected to the abaxial surface. Young galls were red while the mature ones were green. Preferentially, they were formed next to leaf margin and possessed one larval chamber containing a single galling specimen. Gall epidermis was uniseriate, with thicker cuticle and more hairy. In some spots, epidermis was substituted by periderm, which indicated the expression of a character usually absent in the leaf laminas. Morphological and anatomical features of these gall morphotype, such as its position in leaf lamina, the fact of being truly closed galls, with typical nutritive tissue involved by sclerenchyma, made them next to the pattern proposed for galls induced by some Hymenoptera.

Leaf Anatomy of Prosthechea moojenii(Pabst)W.E.Higgins and P.silvana Cath.&V.P.Castro(Orchidaceae)as an Approach to Taxonomy of Species Occurring in Biomes Cerrado and Atlantic Forest of the Bahia

Prosthechea is a neotropical genus, belonging to the family Orchidaceae. The Brazil recorded 32 species of the genus of which nine occur in the state of Bahia, including P. silvana and P. moojenii. The first, P. silvana is epiphytic, endemic Atlantic Forest areas of South and Southeast of the Bahia and morphologically similar to P. moojenii, rupicolous species considered endemic to the Chapada Diamantina. There are doubts whether these two species are really distinct, because they differ only as to the way of life and aspects related to the size of the inflorescence and floral structure. Thus the anatomical study of these two species, emerges as a tool that aims to investigate the delimitation of these taxa. For this study, the sheet was cut freehand with a razor blade to obtain cross sections and treated by chemical means to obtain paradermic sections, all the material was stained with safranine/Astra blue (safrablau) and safranin, respectively, and the sections were then mounted between a semipermanent and cover slipped slides. The results allowed to distinguish P. silvana of the P. moojenii through the following characteristics observed in the leaf (thickening of the cell walls of epidermal cells, amount and disposition of sclerenchyma fibers and fiber arrangement of vascular and vascular bundles in the mesophyll) and root (number of arcs of xylem and phloem, thickening of cells median cortex), infers taxonomic characters for the genus. The data indicated anatomical distinction between the two species studied here of the Prosthechea, however, suggest the anatomical analysis of other organs to reproductive and vegetative.

Finding my way: The role of dirigent proteins in lignin assembly

Lignin emerged around 450 million years ago in early tracheophytes and played a pivotal role in the colonization of terrestrial ecosystems by plants.This aromatic biopolymer provides mechanical strength to supportive tissues and hydrophobicity to water-transporting vasculature and acts as a physical barrier against herbivores and pathogens(Renault et al.,2019).The deposition of lignin in cell walls for proper cellular functionalization involves several molecular steps,including the tight regulation of tissue-or cell-type-specific expression of lignin biosynthetic genes,the biosynthesis of distinct lignin monomers and their transportation to the apoplast,and the polymerization of monomer radicals to produce tissue-or cell-type-dependent polymers with distinct physico-chemical properties.

Physical habitat condition as a key tool to maintain freshwater biodiversity in neotropical artificial ponds

In areas highly affected by anthropogenic disturbances,artificial(human-made)freshwater ecosystems can provide habitat for maintaining and conserving regional freshwater biodiversity.We assessed how the physical habitat of artificial ponds affected the structure of benthic macroinvertebrate assemblages.To do so,we tested two hypotheses.(1)Physical habitat disturbances are not detrimental to the diversity of nearby artificial ponds,and(2)Physical habitat disturbances do not cause significant shifts in taxonomic composition.Our results rejected both null hypotheses,i.e.,macroinvertebrate diversity metrics correlated significantly and positively with Physical Habitat Integrity index scores,and only sites with high habitat condition scores were significantly associated with sensitive indicator taxa.Our results highlight the importance of maintaining physical habitat conditions for sustaining the ecological health of artificial ponds.

New Insights into Aluminum Tolerance in Rice： The ASR5 Protein Binds the STAR1 Promoter and Other Aluminum-Responsive Genes

Aluminum （AI） toxicity in plants is one of the primary constraints in crop production. Al3＋, the most toxic form of Al, is released into soil under acidic conditions and causes extensive damage to plants, especially in the roots. In rice, Al tolerance requires the ASR5 gene, but the molecular function of ASR5 has remained unknown. Here, we perform genome-wide analyses to identify ASR5-dependent Al-responsive genes in rice. Based on ASRS_RNAi silencing in plants, a global transcriptome analysis identified a total of 961 genes that were responsive to Al treatment in wildtype rice roots. Of these genes, 909 did not respond to Al in the ASR5_RNAi plants, indicating a central role for ASR5 in Al-responsive gene expression. Under normal conditions, without Al treatment, the ASR5 RNAi plants expressed 1.756 genes differentially compared to the wild-type plants, and 446 of these genes responded to AI treatment in the wild-type plants. Chromatin immunoprecipitation followed by deep sequencing identified 104 putative target genes that were directly regulated by ASR5 binding to their promoters, including the STAR1 gene, which encodes an ABC transporter required for AI tolerance. Motif analysis of the binding peak sequences revealed the binding motif for ASR5, which was confirmed via in vitro DNA-binding assays using the STAR1 promoter. These results demonstrate that ASR5 acts as a key transcription factor that is essential for AI-responsive gene expression and Al tolerance in rice.

Do assortative mating and immigrant inviability help maintain population genetic structuring of an herbivore on a crop and a wild relative?

Population genetic structuring is common among herbivorous insects and frequently is associated with divergent host plants, such as crops and their wild relatives. Previous studies showed population genetic structuring in corn leafhopper Dulbulus maidis in Mexico, such that the species consists of two sympatric, host plant-associated populations: an abundant and widespread "pestiferous” population on maize (Zea mays mays), and a small and localized "wild" population on perennial teosinte (Zea diploperennis). a maize wild relative with a limited distribution. This study addressed whether assortative mating and immigrant inviability mediate genetic structuring of corn leafliopper by comparing the mating and reproductive successes of pestiferous and wild females that colonize their nonassociated host plants against the successes of females colonizing their associated host plants. Assortative mating was assessed by comparing mating frequencies and premating and mating times among females of each population on each host plant: immigrant inviability was assessed by comparing, across two generations, the fecundity, survival, development time, sex ratio, and population growth rate among leafhopper populations and host plants. Our results showed that on maize, and compared to resident, pestiferous females, wild females were more likely to mate, and greater proportions of their offspring survived to adult stage and were daughters;consequently, the per-generation population growth rate on maize was greater for immigrant, wild leafhoppers compared to resident, pestiferous leafhoppers. Our results suggested that wild leafhoppers emigrating to maize have a fitness advantage over resident, pestiferous leafhoppers, while immigrant pestiferous and resident wild leafhoppers on teosinte have similar fitnesses.