Cell division control protein 42 (CDC42) homolog is a small Rho GTPase enzyme that participates in such processes as cell cycle progression, migration, polarity, adhesion, and transcription. Recent studies suggest that CDC42 is a potent tumor suppressor in different tissues and is related to aging processes. Although DNA damage is crucial in aging, a potential role for CDC42 in genotoxic stress remains to be explored. Migration, survival/proliferation and DNA damage/repair experiments were performed to demonstrate CDC42 involvement in the recovery of HeLa cells exposed to ultraviolet radiation-induced stress. Sub-lines of HeLa cells ectopically expressing the constitutively active CDC42-V12 mutant were generated to examine whether different CDC42-GTP backgrounds might reflect different sensitivities to UV radiation. Our results show that CDC42 constitutive activation does not interfere with HeLa cell migration after UV radiation. However, the minor DNA damage exhibited by the CDC42-V12 mutant exposed to UV radiation most likely results in cell cycle arrest at the G2/M checkpoint and reduced proliferation and survival. HeLa cells and Mock clones, which express endogenous wild-type CDC42 and show normal activity, are more resistant to UV radiation. None of these effects are altered by pharmacological CDC42 inhibition. Finally, the phosphorylation status of the DNA damage response proteins γ-H2AX and p-Chk1 was found to be delayed and attenuated, respectively, in CDC42-V12 clones. In conclusion, the sensitivity of HeLa cells to ultraviolet radiation increases with CDC42 over-activation due to inadequate DNA repair signaling, culminating in G2/M cell accumulation, which is translated into reduced cellular proliferation and survival.

-The goal of this work was to characterize morphometrically diaspores from three species of mistletoes (Passovia pyrifolia, Struthanthus marginatus e Phoradendron mucronatum), as well as to study its germination behavior according to temperature and luminosity. In germination tests, the completely randomized design was used, in factor scheme 4 x 2, with 4 replications of 15 diaspores. The factors for the first test were different temperatures and two diaspore conditions (intact and without epicarp). In the second test, factors were different light qualities and two diaspore conditions. The analyzed variables were: germination percentage, germination rate index (GRI) and mean germination time (MGT). Mistletoe's diaspores present an elliptic shape with viscin layer, an essential characteristic for the dispersion of the species. In addition to this, they present a distinction as for the moisture content when compared to the Loranthaceae and Viscaceae, where the latter presents the highest content. Germination is greater at the alternated temperature of 20-30 o C for P. pyrifolia and P. mucronatum diaspores and 20 o C for S. marginatus. Luminosity interfered in the germination of P. mucronatum and S. marginatus but did not influence P. pyrifolia. The diaspore condition influenced the germination of the three studied species, observing a significant increase in their germination when the epicarp was removed. Temperature and luminosity interfere directly in the GRI and MGT of the three mistletoes species.Keywords: mistletoes, temperature, luminosity. RESUMO -O objetivo deste trabalho foi caracterizar morfometricamente diásporos de três espécies de ervas-de-passarinho (Passovia pyrifolia, Struthanthus marginatus e Phoradendron mucronatum), bem como estudar o seu comportamento germinativo em função de temperatura e luminosidade. Nos ensaios de germinação utilizou-se o delineamento inteiramente casualizado em esquema fatorial 4 x 2, com 4 repetições de 15 diásporos. Os fatores para o primeiro ensaio foram diferentes temperaturas e duas condições do diásporo (intacto e sem epicarpo). No segundo ensaio, os fatores foram diferentes qualidades de luz e duas condições do diásporo. As variáveis analisadas foram: porcentagem de germinação, índice de velocidade de germinação (IVG) e tempo médio de germinação (TMG). Os diásporos de ervas

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Species that have allelopathic potential are promising in agriculture, with the perspective of identifying their secondary metabolites and manipulating them, for practical applications and, thus, be used to control weeds. In this context, this work aimed to verify the allelopathic effect and identify the secondary metabolites in Canavalia ensiformis species. The Lactuca sativa, Digitaria insularis, Emilia coccinea, and Portulaca oleracea species were used as recipient species. To evaluate the allelopathic potential, the ethanolic extract of the shoot (leaf + stem) of the donor species was carried out. Potential allelopathic effects were evaluated by germination tests and initial seedling growth. The identification of the secondary metabolites of the C. ensiformis shoot was also performed using the high-performance liquid chromatography technique. The ethanolic extract causes germination inhibition and germination speed index of L. sativa. The C. ensiformis shoot contains the compounds belonging to phenolic acids (chlorogenic acid, ferulic acid, and caffeic acid), flavonoids (kaempferol, naringin, and rutin), and carboxylic acids (citric, malonic, and aspartic acids), which can be responsible for the allelopathic activity of this species.Keywords: allelopathy; jack bean; phytochemical. RESUMO ABSTRACTPotencial alelopático e identificação dos metabólitos secundários em extratos de Canavalia ensiformis L. 1As espécies que apresentam potencial alelopático são promissoras na agricultura, ante a perspectiva da identificação e manipulação dos seus metabólitos secundários, para aplicações práticas e, assim, sua utilização no controle de plantas daninhas. Por esta razão, este trabalho teve por objetivo verificar o efeito alelopático e identificar os metabólitos secundários de Canavalia ensiformis L. Sementes de Lactuca sativa, Digitaria insularis, Emilia coccinea e Portulaca oleracea foram utilizadas como receptoras. Para avaliar o potencial alelopático, foi preparado o extrato etanólico da parte aérea (folhas mais caules) da espécie doadora. Os efeitos potencialmente alelopáticos foram avaliados por meio de testes de germinação e crescimento inicial de plântulas. Foi realizada, também, por meio da técnica da Cromatografia Líquida de Alta Eficiência, a identificação dos metabólitos secundários da parte aérea de C. ensiformis. O extrato etanólico causa inibição da percentagem e do índice de velocidade de germinação de L. sativa. A parte aérea de C. ensiformis contém ácidos fenólicos (ácido clorogênico, ácido ferúlico, ácido cafeico), flavonoides (kaempferol, naringina e rutina) e ácidos carboxílicos (ácido cítrico, ácido malônico e ácido aspártico), podendo ser os responsáveis pela atividade alelopática dessa espécie.

Several of the methods used to estimate actual evapotranspiration (ET a ) consider the crop evapotranspiration (ET c ) to be affected by a soil water stress co-efficient (K s ) such that ET a = K s ET c . The aim of this study was to assess the ET a estimation in maize in Alagoas State (09 ∘ 38 ′ S and 36 ∘ 40 ′ W; 260 m msl) in northeastern Brazil using the method of the single crop co-efficient from the FAO-56 paper, combined with three different approaches to determine K s . The K s was expressed as either a linear (K s,lin ) or a logarithmic (K s,log ) function of the soil water depletion. Additionally, the method proposed in the FAO-56 (K s,FAO ) was used when the impact was linear, but it was switched on after only one offset. Meteorological and soil water measurements were conducted in a maize crop from July to October 2005. The estimates of ET a were compared with the ET a determined from soil water balance. The ET a estimated with K s,lin had the highest precision (r 2 = 0.67) and accuracy (d = 0.89 and root mean square error (RMSE) = 0.67 mm d −1 ). However, the ET a determined from

-The aim of this research paper was to compare the growth of D. ciliaris and D. nuda crabgrass species under non-competitive conditions. To this end, two experiments were conducted, one from March -July 2010 and the other from February -June 2011. The experimental design of both trials was completely randomized making a factorial (2 seasons x 2 species crabgrass x 12 evaluation periods) with four replications. Assessments began at 15 days after sowing (DAS), and repeated weekly until 92 DAS. The variables evaluated were total dry matter (roots+leaves+stems), leaf area, leaf number and tiller. The results were submitted to analysis of variance and the absolute growth rate, relative growth rate and leaf area ratio were calculated using the means, which were adjusted regression models. The crabgrass species were significantly different in leaf area, leaf number, tiller number and dry matter per plant. D. ciliaris for all variables was statistically higher than D. nuda. Regarding the speed at which the growth of the species occurred, the absolute growth rate and relative growth rate of D. ciliaris was also greater than D. nuda. In addition, D. ciliaris also had a lower leaf area ratio indicating greater efficiency in converting light energy into carbohydrates. It can be concluded that D. ciliaris has a higher growth rate in conditions where there is no limitation of nutrients and water availability in relation to D. nuda, mainly due to D. ciliaris have greater leaf area, number of leaves and dry matter accumulation per plant.

The objective of the present work was to study the influence of temperature and light on germination of seeds of Stigmaphyllon blanchetii, popularly known as rat tail. The first stage of the research evaluated the effect of three constant temperatures (20 oC, 25 oC and 30 oC) and an alternating temperature (20-30 oC). In the second stage, for simulation of different types of light, four conditions of luminosity (white, red, far red and absence of light) were used. The temperatures that provided the best germination and development for S. blanchetii are the constant (30 oC) and the alternating (20-30 oC) ones. The seeds germinated both in the presence and absence of light, but there was greater germination and seedling development in the absence of light; thus they were classified as preferential negative photoblastic seeds.

The allelopathic potential of some plant species has been scientifically proven over the years. The use of such natural compounds with phytotoxic activity is an alternative to synthetic herbicides. Thus, this research aims to analyze the phytochemical profile and the allelopathic effect of aqueous extracts of Fimbristylis miliacea (L.) Vahl. The allelopathic potential was evaluated by germination bioassays using seeds from two receptor species (Lactuca sativa L. and Emilia fosbergii Nicolson) and seven concentrations of aqueous extracts of F. miliacea aerial and underground parts in triplicate. The variables evaluated were germination (G) andJournal of Agricultural Studies 311 germination speed index (GSI). The data obtained were submitted to F test and the averages to regression analysis. In addition, phytochemical analyses were performed to analyze possible allelochemicals present in aqueous extracts of F. miliacea through phytochemical screening and by high performance liquid chromatography (HPLC). The aqueous extracts of aerial and underground parts of F. miliacea inhibit the germination of E. fosbergii seeds at all concentrations analyzed (0.94, 1.87, 3.75, 7.5, 15 and 30%). However, the same extracts do not show any effects when evaluated in L. sativa seeds. The aqueous extract of F. miliacea shows important chemical constituents (gallic acid, chlorogenic acid, rutin, luteolin, apigenin, acacetin, and alkaloids) that can be directly related to the allelopathic effects observed in E. fosbergii seeds.