EgPHI-1, a PHOSPHATE-INDUCED-1 gene from Eucalyptus globulus, is involved in shoot growth, xylem fiber length and secondary cell wall properties.

MAIN CONCLUSION: EgPHI-1 is a member of PHI-1/EXO/EXL protein family. Its overexpression in tobacco resulted in changes in biomass partitioning, xylem fiber length, secondary cell wall thickening and composition, and lignification. Here, we report the functional characterization of a PHOSPHATE-INDUCED PROTEIN 1 homologue showing differential expression in xylem cells from Eucalyptus species of contrasting phenotypes for wood quality and growth traits. Our results indicated that this gene is a member of the PHI-1/EXO/EXL family. Analysis of the promoter cis-acting regulatory elements and expression responses to different treatments revealed that the Eucalyptus globulus PHI-1 (EgPHI-1) is transcriptionally regulated by auxin, cytokinin, wounding and drought. EgPHI-1 overexpression in transgenic tobacco changed the partitioning of biomass, favoring its allocation to shoots in detriment of roots. The stem of the transgenic plants showed longer xylem fibers and reduced cellulose content, while the leaf xylem had enhanced secondary cell wall thickness. UV microspectrophotometry of individual cell wall layers of fibers and vessels has shown that the transgenic plants exhibit differences in the lignification of S2 layer in both cell types. Taken together, the results suggest that EgPHI-1 mediates the elongation of secondary xylem fibers, secondary cell wall thickening and composition, and lignification, making it an attractive target for biotechnological applications in forestry and biofuel crops.

Effect of termite activity on soil under different land management strategies / Efeito da atividade de térmitas no solo sob diferentes manejos

Mound-building termites are important agents of soil bioperturbation, but these species have not been extensively studied thus far. The present study aimed to evaluate the soil particle-size and the chemical attributes of termite mounds and the surrounding soil under different land use strategies. A one-hectare plot was defined for an unmanaged degraded pasture, planted pasture, and for a eucalyptus Corymbia citriodora plantation. In each plot, the top, center, and base sections of five Cornitermes cumulans mounds, and the surrounding soil at the depths of 0-5; 5-10; 10-20 cm, were sampled in the Pinheiral, Rio de Janeiro state. In the three areas, the center of the mounds contained higher clay content, organic carbon, phosphorous, calcium and magnesium, total bases, and cation exchangeable capacity, when compared to the top, base, and the surrounding soils. However, the center had lower values of exchangeable acidity and potassium, of the three areas. In the eucalyptus plantation, the values of pH, total bases, calcium, and magnesium were lower, whereas aluminum, exchangeable acidity, sodium, and cation exchange capacity were higher both in the mounds and in the surrounding soil, in relation to the pastures. There were no differences among the three areas in terms of organic carbon, potassium, phosphorous, and total bases, in the mounds and adjacent soil. Thus, the termite activity altered the clay content and most of the soil chemical properties in all of the studied areas, but only for the center of the mounds. However, the effect of these organisms was different in the eucalyptus plantation in relation to the pasture areas.(AU)

Térmitas construtores de montículos são importantes agentes modificadores do solo, mas estudos são necessários para a melhor compreensão deste processo. O presente estudo objetivou avaliar a granulometria e os atributos químicos do material formador de montículos de térmitas e compará-los com o solo adjacente não trabalhado pelos organismos, em diferentes tipos de manejo do solo. Coletouse o material individualizado em topo, base e centro de cinco montículos de Cornitermes cumulans, bem como do solo adjacente não trabalhado (camadas de 0-5, 5-10 e 10-20 cm), em 1 ha demarcado em áreas de pastagem não manejada degradada, pastagem formada e plantio do eucalipto Corymbia citriodora, em Pinheiral, RJ. Nestas três áreas, a seção central dos montículos apresentou maiores valores de conteúdo de argila, carbono orgânico, fósforo, cálcio e magnésio, soma de bases e capacidade de troca catiônica, em comparação com o topo, base e o solo adjacente. Contudo, no centro dos montículos observou-se menores valores de acidez extraível e potássio, em relação ao topo, base e o solo adjacente nas áreas estudadas. No plantio de eucalipto, os valores de pH, soma de bases, cálcio e magnésio foram menores, enquanto que os valores de alumínio, acidez extraível, sódio e capacidade de troca catiônica foram maiores, nos termiteiros e no solo adjacente, quando comparado com as pastagens. Não houve diferença entre as áreas estudadas quanto aos valores de carbono orgânico, potássio, fósforo e soma de bases, nos montículos e no solo adjacente. Assim, a atividade dos térmitas alterou o conteúdo de argila e a maioria dos atributos químicos do solo em todas as áreas estudadas, mas apenas no centro dos termiteiros. Contudo, o efeito destes organismos foi diferente no plantio de eucalipto, em relação às pastagens.(AU)

Effect of termite activity on soil under different land management strategies / Efeito da atividade de térmitas no solo sob diferentes manejos

Mound-building termites are important agents of soil bioperturbation, but these species have not been extensively studied thus far. The present study aimed to evaluate the soil particle-size and the chemical attributes of termite mounds and the surrounding soil under different land use strategies. A one-hectare plot was defined for an unmanaged degraded pasture, planted pasture, and for a eucalyptus Corymbia citriodora plantation. In each plot, the top, center, and base sections of five Cornitermes cumulans mounds, and the surrounding soil at the depths of 0-5; 5-10; 10-20 cm, were sampled in the Pinheiral, Rio de Janeiro state. In the three areas, the center of the mounds contained higher clay content, organic carbon, phosphorous, calcium and magnesium, total bases, and cation exchangeable capacity, when compared to the top, base, and the surrounding soils. However, the center had lower values of exchangeable acidity and potassium, of the three areas. In the eucalyptus plantation, the values of pH, total bases, calcium, and magnesium were lower, whereas aluminum, exchangeable acidity, sodium, and cation exchange capacity were higher both in the mounds and in the surrounding soil, in relation to the pastures. There were no differences among the three areas in terms of organic carbon, potassium, phosphorous, and total bases, in the mounds and adjacent soil. Thus, the termite activity altered the clay content and most of the soil chemical properties in all of the studied areas, but only for the center of the mounds. However, the effect of these organisms was different in the eucalyptus plantation in relation to the pasture areas.

Térmitas construtores de montículos são importantes agentes modificadores do solo, mas estudos são necessários para a melhor compreensão deste processo. O presente estudo objetivou avaliar a granulometria e os atributos químicos do material formador de montículos de térmitas e compará-los com o solo adjacente não trabalhado pelos organismos, em diferentes tipos de manejo do solo. Coletouse o material individualizado em topo, base e centro de cinco montículos de Cornitermes cumulans, bem como do solo adjacente não trabalhado (camadas de 0-5, 5-10 e 10-20 cm), em 1 ha demarcado em áreas de pastagem não manejada degradada, pastagem formada e plantio do eucalipto Corymbia citriodora, em Pinheiral, RJ. Nestas três áreas, a seção central dos montículos apresentou maiores valores de conteúdo de argila, carbono orgânico, fósforo, cálcio e magnésio, soma de bases e capacidade de troca catiônica, em comparação com o topo, base e o solo adjacente. Contudo, no centro dos montículos observou-se menores valores de acidez extraível e potássio, em relação ao topo, base e o solo adjacente nas áreas estudadas. No plantio de eucalipto, os valores de pH, soma de bases, cálcio e magnésio foram menores, enquanto que os valores de alumínio, acidez extraível, sódio e capacidade de troca catiônica foram maiores, nos termiteiros e no solo adjacente, quando comparado com as pastagens. Não houve diferença entre as áreas estudadas quanto aos valores de carbono orgânico, potássio, fósforo e soma de bases, nos montículos e no solo adjacente. Assim, a atividade dos térmitas alterou o conteúdo de argila e a maioria dos atributos químicos do solo em todas as áreas estudadas, mas apenas no centro dos termiteiros. Contudo, o efeito destes organismos foi diferente no plantio de eucalipto, em relação às pastagens.

First insights into the functional role of vasicentric tracheids and parenchyma in eucalyptus species with solitary vessels: do they contribute to xylem efficiency or safety?

The relationship between hydraulic specific conductivity (ks) and vulnerability to cavitation (VC) with size and number of vessels has been studied in many angiosperms. However, few of the studies link other cell types (vasicentric tracheids (VT), fibre-tracheids, parenchyma) with these hydraulic functions. Eucalyptus is one of the most important genera in forestry worldwide. It exhibits a complex wood anatomy, with solitary vessels surrounded by VT and parenchyma, which could serve as a good model to investigate the functional role of the different cell types in xylem functioning. Wood anatomy (several traits of vessels, VT, fibres and parenchyma) in conjunction with maximum ks and VC was studied in adult trees of commercial species with medium-to-high wood density (Eucalyptus globulus Labill., Eucalyptus viminalis Labill. and Eucalyptus camaldulensis Dehnh.). Traits of cells accompanying vessels presented correlations with functional variables suggesting that they contribute to both increasing connectivity between adjacent vessels-and, therefore, to xylem conduction efficiency-and decreasing the probability of embolism propagation into the tissue, i.e., xylem safety. All three species presented moderate-to-high resistance to cavitation (mean P50 values = -2.4 to -4.2 MPa) with no general trade-off between efficiency and safety at the interspecific level. The results in these species do not support some well-established hypotheses of the functional meaning of wood anatomy.

Estimating chlorophyll content from Eucalyptus dunnii leaves by reflectance values / Estimativa da concentração de pigmentos clorofilianos em folhas de Eucalyptus dunnii por valores de refletância

This study aimed to estimate photosynthetic pigments contents from leaves of Eucalyptus dunni Maiden based on values of reflectance spectra of red, green and blue colors obtained with a digital color analyzer. We collected fifty leaves from the lower third of the crown of twenty trees including young as well as mature leaves. From each leaf an area of 14 cm2 of the leaf blade was cut in which we measured reflectance values on the red, green and blue spectra with a portable digital colorimeter, obtained relative index of chlorophyll with a SPAD 502 and determined the content of the chlorophyll a, b, and a + b by classic method of solvent extraction. We submitted the data to multiple linear regression and nonlinear analysis at 5% of error probability. It was evaluated the occurrence of multicollinearity. The negative exponential model resulted in good fit when data from red spectrum was used for chlorophyll a, green spectrum for chlorophyll b and a + b, making possible correlation coefficients between the estimated values and the extracted above 0.85. Except for the chlorophyll a content, the accuracy in estimates of photosynthetic pigments were higher than estimated by the chlorophyll meter, even with linearity between methods. Therefore, it is possible to estimate photosynthetic pigments on E. dunni leaves through values of red and green wavelengths from a digital color...

O presente trabalho objetivou estimar a concentração de pigmentos clorofilianos em folhas de Eucalyptus dunni Maiden com base nos valores de refletância de cores no espectro eletromagnético no vermelho, verde e azul obtidos por um analisador de cores. Cinquenta folhas coletadas do terço inferior da copa de vinte árvores foram utilizadas abrangendo folhas jovens até folhas em processo de abscisão. De cada folha foi retirada uma área de 14 cm2 de limbo foliar, e nesta mensurados os valores da refletância no espectro na faixa do vermelho, verde e azul com um colorímetro portátil, obtido o índice relativo de clorofila com um SPAD 502 e determinada a concentração de clorofila a, b e a + b pelo método clássico de extração por solvente. Os resultados foram submetidos a análise de regressão linear múltipla e não linear a 5% de probabilidade de erro. Avaliou-se a ocorrência de multicolinearidade. Dos modelos ajustados foi realizada uma análise dos resíduos e correlacionados com a concentração extraída. Houve multicolinearidade entre os valores do espectro de cores, inviabilizando a estimativa das clorofilas por um modelo linear múltiplo. O modelo exponencial negativo possuiu maior aderência, quando utilizados os valores do espectro vermelho para a concentração de clorofila a, e do verde para a concentração de clorofila b e a + b, possibilitando coeficientes de correlação entre os...

Estimating chlorophyll content from Eucalyptus dunnii leaves by reflectance values / Estimativa da concentração de pigmentos clorofilianos em folhas de Eucalyptus dunnii por valores de refletância

This study aimed to estimate photosynthetic pigments contents from leaves of Eucalyptus dunni Maiden based on values of reflectance spectra of red, green and blue colors obtained with a digital color analyzer. We collected fifty leaves from the lower third of the crown of twenty trees including young as well as mature leaves. From each leaf an area of 14 cm2 of the leaf blade was cut in which we measured reflectance values on the red, green and blue spectra with a portable digital colorimeter, obtained relative index of chlorophyll with a SPAD 502 and determined the content of the chlorophyll a, b, and a + b by classic method of solvent extraction. We submitted the data to multiple linear regression and nonlinear analysis at 5% of error probability. It was evaluated the occurrence of multicollinearity. The negative exponential model resulted in good fit when data from red spectrum was used for chlorophyll a, green spectrum for chlorophyll b and a + b, making possible correlation coefficients between the estimated values and the extracted above 0.85. Except for the chlorophyll a content, the accuracy in estimates of photosynthetic pigments were higher than estimated by the chlorophyll meter, even with linearity between methods. Therefore, it is possible to estimate photosynthetic pigments on E. dunni leaves through values of red and green wavelengths from a digital color...(AU)

O presente trabalho objetivou estimar a concentração de pigmentos clorofilianos em folhas de Eucalyptus dunni Maiden com base nos valores de refletância de cores no espectro eletromagnético no vermelho, verde e azul obtidos por um analisador de cores. Cinquenta folhas coletadas do terço inferior da copa de vinte árvores foram utilizadas abrangendo folhas jovens até folhas em processo de abscisão. De cada folha foi retirada uma área de 14 cm2 de limbo foliar, e nesta mensurados os valores da refletância no espectro na faixa do vermelho, verde e azul com um colorímetro portátil, obtido o índice relativo de clorofila com um SPAD 502 e determinada a concentração de clorofila a, b e a + b pelo método clássico de extração por solvente. Os resultados foram submetidos a análise de regressão linear múltipla e não linear a 5% de probabilidade de erro. Avaliou-se a ocorrência de multicolinearidade. Dos modelos ajustados foi realizada uma análise dos resíduos e correlacionados com a concentração extraída. Houve multicolinearidade entre os valores do espectro de cores, inviabilizando a estimativa das clorofilas por um modelo linear múltiplo. O modelo exponencial negativo possuiu maior aderência, quando utilizados os valores do espectro vermelho para a concentração de clorofila a, e do verde para a concentração de clorofila b e a + b, possibilitando coeficientes de correlação entre os...(AU)

A model system to study the lignification process in Eucalyptus globulus.

Recalcitrance of plant biomass is closely related to the presence of the phenolic heteropolymer lignin in secondary cell walls, which has a negative effect on forage digestibility, biomass-to-biofuels conversion and chemical pulping. The genus Eucalyptus is the main source of wood for pulp and paper industry. However, when compared to model plants such as Arabidopsis thaliana and poplar, relatively little is known about lignin biosynthesis in Eucalyptus and only a few genes were functionally characterized. An efficient, fast and inexpensive in vitro system was developed to study lignification in Eucalyptus globulus and to evaluate the potential role of candidate genes in this biological process. Seedlings were grown in four different conditions, in the presence or absence of light and with or without sucrose in the growth medium, and several aspects of lignin metabolism were evaluated. Our results showed that light and, to a lesser extent, sucrose induced lignin biosynthesis, which was followed by changes in S/G ratio, lignin oligomers accumulation and gene expression. In addition, higher total peroxidase activity and differential isoperoxidase profile were observed when seedlings were grown in the presence of light and sucrose. Peptide sequencing allowed the identification of differentially expressed peroxidases, which can be considered potential candidate class III peroxidases involved in lignin polymerization in E. globulus.

The tonoplast intrinsic aquaporin (TIP) subfamily of Eucalyptus grandis: Characterization of EgTIP2, a root-specific and osmotic stress-responsive gene.

Aquaporins have important roles in various physiological processes in plants, including growth, development and adaptation to stress. In this study, a gene encoding a root-specific tonoplast intrinsic aquaporin (TIP) from Eucalyptus grandis (named EgTIP2) was investigated. The root-specific expression of EgTIP2 was validated over a panel of five eucalyptus organ/tissues. In eucalyptus roots, EgTIP2 expression was significantly induced by osmotic stress imposed by PEG treatment. Histochemical analysis of transgenic tobacco lines (Nicotiana tabacum SR1) harboring an EgTIP2 promoter:GUS reporter cassette revealed major GUS staining in the vasculature and in root tips. Consistent with its osmotic-stress inducible expression in eucalyptus, EgTIP2 promoter activity was up-regulated by mannitol treatment, but was down-regulated by abscisic acid. Taken together, these results suggest that EgTIP2 might be involved in eucalyptus response to drought. Additional searches in the eucalyptus genome revealed the presence of four additional putative TIP coding genes, which could be individually assigned to the classical TIP1-5 groups.

Leaf anatomy and morphometry in three eucalypt clones treated with glyphosate.

This work aimed to evaluate the effects of simulated drift of glyphosate on the morphoanatomy of three eucalypt clones and to correlate the intoxication symptoms on a microscopic scale with those observed in this visual analysis. The effects of glyphosate drift were proportional to the five doses tested, with Eucalyptus urophylla being more tolerant to the herbicide than E. grandis and urograndis hybrid. The symptoms of intoxication which were similar for the different clones at 7 and 15 days after application were characterized by leaf wilting, chlorosis and curling and, at the highest rates, by necrosis, leaf senescence and death. Anatomically glyphosate doses higher than 86.4 g.ha-1 caused cellular plasmolysis, hypertrophy and hyperplasia, formation of the cicatrization tissue and dead cells on the adaxial epidermis. The spongy parenchyma had a decrease, and the palisade parenchyma and leaf blade thickness had an increase. The increased thickness in leaf blade and palisade parenchyma may be related to the plant response to glyphosate action, as a form of recovering the photosynthetically active area reduced by necroses and leaf senescence caused by the herbicide.

Live biospeckle laser imaging of root tissues.

Live imaging is now a central component for the study of plant developmental processes. Currently, most techniques are extremely constraining: they rely on the marking of specific cellular structures which generally apply to model species because they require genetic transformations. The biospeckle laser (BSL) system was evaluated as an instrument to measure biological activity in plant tissues. The system allows collecting biospeckle patterns from roots which are grown in gels. Laser illumination has been optimized to obtain the images without undesirable specular reflections from the glass tube. Data on two different plant species were obtained and the ability of three different methods to analyze the biospeckle patterns are presented. The results showed that the biospeckle could provide quantitative indicators of the molecular activity from roots which are grown in gel substrate in tissue culture. We also presented a particular experimental configuration and the optimal approach to analyze the images. This may serve as a basis to further works on live BSL in order to study root development.

Leaf anatomy and morphometry in three eucalypt clones treated with glyphosate / Anatomia e morfometria foliar em clones de eucalipto tratados com glyphosate

This work aimed to evaluate the effects of simulated drift of glyphosate on the morphoanatomy of three eucalypt clones and to correlate the intoxication symptoms on a microscopic scale with those observed in this visual analysis. The effects of glyphosate drift were proportional to the five doses tested, with Eucalyptus urophylla being more tolerant to the herbicide than E. grandis and urograndis hybrid. The symptoms of intoxication which were similar for the different clones at 7 and 15 days after application were characterized by leaf wilting, chlorosis and curling and, at the highest rates, by necrosis, leaf senescence and death. Anatomically glyphosate doses higher than 86.4 g.ha-1 caused cellular plasmolysis, hypertrophy and hyperplasia, formation of the cicatrization tissue and dead cells on the adaxial epidermis. The spongy parenchyma had a decrease, and the palisade parenchyma and leaf blade thickness had an increase. The increased thickness in leaf blade and palisade parenchyma may be related to the plant response to glyphosate action, as a form of recovering the photosynthetically active area reduced by necroses and leaf senescence caused by the herbicide.

Este trabalho teve como objetivo avaliar os efeitos da deriva simulada de glyphosate na morfoanatomia de três clones de eucalipto e correlacionar os sintomas de intoxicação em escala microscópica com aqueles observados à vista desarmada. Os efeitos da deriva do glyphosate foram proporcionais às doses testadas, sendo Eucalyptus urophylla mais tolerante ao herbicida que E. grandis e o híbrido urograndis. Os sintomas de intoxicação foram semelhantes para os diferentes clones testados, tanto aos 7 quanto aos 15 dias após a aplicação, sendo caracterizados, morfologicamente, por murcha, clorose e enrolamento foliar e, no caso das maiores doses, por necrose, senescência foliar e morte das plantas de eucalipto. Anatomicamente, doses de glyphosate superiores a 86,4 g.ha-1 provocaram plasmólise, hipertrofia e hiperplasia celular, formação de tecido de cicatrização e morte das células da face adaxial da epiderme. Observou-se diminuição na espessura do parênquima lacunoso e aumento na espessura do parênquima paliçádico e da lâmina foliar. O aumento na espessura da folha e do parênquima paliçádico podem estar relacionados à resposta das plantas ao glyphosate, como forma de compensar a área fotossinteticamente reduzida pelas necroses e senescência causadas pelo herbicida.