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Stylosanthes, a genus of tropical forage legume, is known to exhibit good persistence in saline soils, yet mechanisms for regulation of seed germination under salt stress are poorly understood. This study was carried out to evaluate the mode of action of salt stress on seed germination of Stylosanthes. 1-Aminocyclopropane-1-carboxylic acid (ACC) increased ethylene biosynthesis and germination of NaCl-inhibited seeds in a dose-dependent manner. Contents of ACC and germination of Stylosanthes humilis seeds increased following transfer from NaCl solution to deionised water, but not after transfer to l-α-(2-aminoethoxyvinyl)-glycine (AVG) solution, an inhibitor of ethylene biosynthesis. Ethylene biosynthesis was much larger in NaCl-treated seeds of Stylosanthes guianensis than in seeds of S. humilis and Stylosanthes capitata, a fact which was reflected in higher germination rates. S. guianensis seedlings also displayed higher growth and survival rates than S. humilis and S. capitata under salt stress. Moreover, smaller ACC levels, as well as reduced ethylene biosynthesis of S. capitata seeds were accompanied by lower germination under salt stress. In addition, S. capitata seedlings treated with NaCl solutions exhibited relatively lower growth and survival rates in comparison with S. humilis and S. guianensis. Thus, different abilities to synthesize ethylene by S. guianensis, S. humilis and S. capitata seeds explain the differences in tolerance to salt stress of the three species.

The effects of varying intensities of light on plants depend on when they occur, even if the total amount of light received is kept constant. We designed an experiment using two clones of robusta coffee (Coffea canephora) intercropped with shelter trees in such a way that allowed us to compare coffee bushes shaded in the morning (SM) with those shaded in the afternoon (SA), and then confronting both with bushes receiving full sunlight over the course of the day (FS). The SM bushes displayed better gas-exchange performance than their SA and FS counterparts, in which the capacity for CO2 fixation was mainly constrained by stomatal (SA bushes) and biochemical (FS bushes) factors. Physiological traits associated with light capture were more responsive to temporal fluctuations of light rather than to the amount of light received, although this behavior could be a clone-specific response. The activity of key antioxidant enzymes differed minimally when comparing the SM and SA clones, but was much larger in FS clones. No signs of photoinhibition or cell damage were found regardless of the light treatments. Acclimations to varying light supplies had no apparent additional cost for constructing and maintaining the leaves regardless of the light supply. Both the SM and SA individuals displayed higher return in terms of revenue streams (e.g. higher mass-based light-saturated photosynthetic rates, photosynthetic nitrogen use efficiencies and long-term water use efficiencies) than their FS counterparts. In conclusion, shading may improve the physiological performance of coffee bushes growing in harsh, tropical environments.

The economics of coffee plantations is intrinsically linked to pruning, which can improve the canopy architecture and thereby increase productivity. However, recommended pruning times on conilon coffee plantations have been made on an entirely empirical basis. In this study, by evaluating growth, photosynthetic gas exchanges, starch accumulation and crop productivity, the effects of pruning at different times between harvest and flowering were investigated for six conilon coffee clones with distinct stages of fruit maturation (early, intermediate and late). Clones with an early maturation stage were pruned at four different times: 0, 30, 60 and 90 days after harvest (DAH). Intermediate clones were pruned at 0, 30 and 60 DAH, and late clones were pruned at 0 and 30 DAH. Overall, the rates of shoot growth and net photosynthesis, the stomatal conductance and the crop yield were not affected by the pruning treatments in any of the clones. In addition, pruning times did not affect the concentrations of starch or the photochemical efficiency of photosystem II. The carbon isotope composition ratio was marginally affected by the treatments. These results suggest that the pruning time after harvests is relatively unimportant and pruning operations can be scheduled to optimise the use of labour, which directly impacts the production costs of coffee. I N T RO D U C T I O NAfter oil products, coffee is the second most commonly traded commodity worldwide. On a broader scale, when all steps from cultivation to the sale of final consumable products are considered, the international coffee trade involves approximately 500 million people (DaMatta et al., 2010). Of the approximately 100 species of the genus Coffea (Davis et al., 2006), only C. arabica L. (arabica coffee) and C. canephora Pierre ex A. Froehner (robusta coffee) are economically important worldwide; these two species are responsible for 99% of world bean production. Currently, arabica

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RESUMO -As propriedades físicas do solo são importantes indicadores de sua qualidade, visto que as plantas necessitam de solos bem estruturados para seu adequado desenvolvimento. Objetivou-se avaliar as propriedades físicas do solo sob diferentes sistemas. O experimento foi realizado em São Mateus-ES. Foram avaliadas as propriedades físicas do solo em dois sistemas: pastejo rotacionado e pastagem degradada em duas profundidades. Os dados oriundos dos diferentes sistemas foram submetidos à análise estatística pelo teste T de Student a 5 % de probabilidade. Foram observados maiores valores absolutos de densidade na área de pastejo rotacionado, tanto na profundidade de 0-5 cm quanto na de 5-20 cm. A área com lotação rotacionada, apresentou maior resistência à penetração na camada de 0-5 cm, com uma camada de compactação de 5,54 MPa, quando comparada à pastagem degradada na mesma profundidade com 1,21 Mpa, provavelmente devido às diferentes formas de uso e preparo do solo. O solo sob pastagem degradada apresentou maior quantidade de poros total nas duas profundidades analisadas. Como consequência, o teor de macroporos foi similarmente superior no solo com pastagem degradada com a tendência de maiores teores na camada de 5-20cm. O diâmetro médio geométrico variou entre 3,78 e 4,29 mm O solo com pastagem de sistema rotacionado apresentou média superior à área de pastagem degradada na profundidade de 5-20 cm, indicando maior estabilidade de agregados nesses sistemas e evidenciando as vantagens do sistema em rotação. O teor de matéria orgânica variou pouco entre os tratamentos na camada superficial. Houve uma compensação nos atributos físicos que refletem a capacidade de retenção de água no solo, resultando em umidade na capacidade de campo semelhante para a lotação rotacionada e a pastagem degradada.Palavras-chave: área degradada, capim-marandu, capim-mombaça, compactação, pisoteio animal. SOIL PHYSICAL PROPERTIES DUE TO DIFFERENT PASTURE MANAGEMENTS

& Key message Hypoxia promoted distinct changes in the levels of hormones, amino acids and organic acids in the roots and shoots of a seedling from 2 Eucalyptus clones. These results indicate that modulation of hormone production, as well as specific chemical constituents associated with primary metabolism, contributes to the regulation of growth of Eucalyptus seedlings under hypoxic conditions. & Context Although floods in areas under Eucalyptus cultivation in Brazil negatively affect plant growth, chemical markers and/ or indicators of hypoxia contributes to the regulation.s & Aims This study aimed to evaluate the hormonal and metabolic alterations induced by hypoxia on seedling growth. & Methods Seedlings of Eucalyptus urograndis clones VCC 975 and 1004 were grown in liquid solution and submitted to bubbling with air or with nitrogen. Levels of indol-3-acetic acid (IAA), abscisic acid (ABA), ethylene, 1-aminocyclopropane-1-carboxylic acid (ACC), primary metabolite profile and photosynthetic parameters were evaluated after fourteen days. & Results Hypoxia did not affect shoot dry mass of the seedlings. However, it decreased stomatal conductance and photosynthetic CO 2 assimilation rate, and increased levels of ABA in the shoot. Hypoxia greatly reduced the dry mass and volume of roots, concomitantly with higher ACC and ethylene production. Moreover, hypoxia promoted distinct changes in IAA levels, and in amino acid and organic acid metabolism in roots and shoots. & Conclusion The biosynthesis of ABA, ethylene and IAA and its quantity in root tissues indicates the regulation of metabolism in response to hypoxia in Eucalyptus clones. Handling Editor: Erwin DreyerContribution of the co-authors: EFM designed, executed the study, and was the main contributor to the writing of the manuscript. Gustavo CV MAYRINK and Cleide R DIAS contributed to maintaining and completing the experiment. Camilo E VITAL performed the LC-MS analysis. Dimas M RIBEIRO, Ivo R SILVA, and Andrew MERCHANT assisted in the design of the experiment, analysis of the results and composition of the paper.Electronic supplementary material The online version of this article (https://doi.

O trabalho teve como objetivo avaliar o aporte e a taxa de decomposição da serapilheira. O estudo foi conduzido em Miraí (MG), no período de outubro de 2013 a setembro de 2015. Foi utilizado o delineamento em blocos casualizados no esquema de parcelas subdivididas, com três repetições. As parcelas receberam diferentes coberturas arbóreas, sendo o primeiro tratamento composto exclusivamente, por eucalipto (Eucaliptus urograndis) (PE), o segundo por angico vermelho (Anadentheramacrocarpa) (PA), enquanto o terceiro envolveu 16 espécies nativas da região (PM). As subparcelas receberam diferentes tipos de adubações. A avaliação da produção de serapilheira foi realizada pela instalação de coletores com 4 m² suspensos 0,5 m acima do solo, alocados nas entrelinhas de plantio, totalizando três coletores por subparcela. A quantidade de serapilheira acumulada no solo foi determinada com o auxílio de um gabarito de 0,25 m², lançado cinco vezes aleatoriamente nas subparcelas. Os dados foram submetidos à análise de variância e as médias comparadas pelo teste Tukey a 10 % de probabilidade. O PE foi o que apresentou maior aporte mensal de serapilheira, enquanto PA foi o menor. O tipo de adubação não influenciou significativamente o aporte total e médio da serapilheira. Na interação da cobertura florestal com a época do ano, houve influência significativa na produção de serapilheira do PM, com maior produção na época seca. A taxa de decomposição doPA e do PM foram influenciadas significativamente pela interação cobertura florestal x época do ano, com maior taxa de decomposição na época chuvosa.