ABSTRACT:The adoption of cover crops in commercial plantations has been shown to be an alternative to promote greater soil protection, enhancement in its structure and aggregation, optimization of accumulation and nutrient cycling to obtain greater production of biomass and higher nitrogen fixation. To determine the accumulation of micronutrients of Pueraria phaseoloides L., according to age, established as a soil cover in industrial oil palm crops, an experiment was carried out at Companhia Agroindustrial (CRAI) in the municipality of Tailândia, State of Pará, in an Oxisol. The experimental design was a randomized block with four replicates. The results allow to conclude that the accumulation of nutrients, except for Mn and Cu in the live Pueraria phaseoloides L. plant cover reduced over the years and those of B, Mn, Zn, and Cu were greater in the dead Pueraria phaseoloides L. plant cover and for Cl it was in the live Pueraria phaseoloides L. plant cover. The decreasing order of total micronutrient extraction was the following: Cl> Mn> B> Zn> Cu.

The aim of this work was to evaluate, by the physiological and growth variables, the behavior of paricá seedlings submitted to cadmium aplications. Cadmium is a importante metal due the industrial use, the accumulation in the environment, the high mobility in the soil-plant system, and possibly by changing physiological and growth parameters in plants. Among the plants that can be affected by this metal is the species (Schizolobium amazonicum Huber ex Ducke), known as paricá. Native from the amazona region, presents great social, economic and environmental potential. Among the physiological variables analyzed, cadmium interfered with photosynthesis, stomatal conductance and transpiration, mainly with the increase of the concentrations of this element. Among the correlated variables, the variable intrinsic efficiency of water use (EiUA), presented high in the stress conditions maintaining the minimum of water balance. For the growth variables, the cadmium provided a decrease in the height, diameter, number of leaves and leaflets influencing the low synthesis of photoassimilates. The phytotoxic element was mainly concentrated in the roots, but there was translocation to shoot, signaling a phytoextractive characteristic.

The aims of study were to evaluate growth and characterize the visual symptoms of macronutrient and micronutrient deficiencies in mangosteens. The seedlings were cultivated in nutritive solution containing all required macronutrient and micronutrients and in solutions with omission of N,

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The experiment was conducted in a greenhouse at the Federal Rural University of Amazonia (UFRA) from November 2011 to July 2012. The plants were subjected to two water regimes: control (adequate irrigation) and water deficiency (water suspension) for 0, 10, 20 and 30 days period. The water potential in stressed plants was reduced after 30 days of drought. The photosynthetic rate, stomatal conductance and transpiration rate were reduced with increased water stress time in plant with more pronounced reductions in the 20 th and 30 th after induction of treatments. The concentration of ABA increased in leaves and roots of plants submitted to water deficit. Dry mass of shoot, root and total mass were decreased in plants under water stress. The suspension of irrigation for 10 days was sufficient to alter the metabolism of young Acapu plants. These results showed that young Acapu plants tolerate a water potential of up to -2.86 MPa, indicating that this species is not susceptible to water stress/suspension. This condition may favor the development and expansion of Voucapoua americana for the recovery of degraded areas in regions with limited available water.

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Water stress limits the initial growth and development of maize mass and grain, as well as the physiological process for absorbing the amount of mineral elements. The objective was to evaluate the effect of silicon on germination and growth of corn seedlings submitted to water deficit. The experiment was carried out in the laboratory and the experimental design was completely randomized (factorial 3 × 4), with three concentrations of calcium silicate (0.0; 1.0 and 2.0 mM) and 4 solutions of PEG-6000 to simulate different osmotic potentials (0, 0; -0.3; -0.6; -0.9 MPa). Germination percentage, germination speed index (GSI), mean germination time (MGT), percentage of non-germinated and abnormal germinated, length and dry matter of shoot, root and total seedlings were evaluated. Water deficiency reduced the parameters TG, GSI and MGT. The water deficit reduce the MSPA, MSR and MST with more than 80% reduction in mass from seedlings without deficiency to seedlings with deficiency. For CPA, CR and CT there was a reduction of at least 87%, 70% and 77%, respectively, among seeds without deficiency compared to seeds submitted to deficiency. The use of silicon in corn seeds did not attenuate the stress caused by water deficit simulated by PEG-6000.

The aim of this work was to evaluate the attenuating effect of the nitric oxide donor (sodium nitroprusside-NPS) on the ecophysiological responses of corn plants (Zea mays L.) submitted to copper toxicity. The corn seeds of the K9606 VIP3 variety were soaked for 48 hours in Germitest with solution containing treatment with sodium nitroprusside Na2 [Fe (CN) 5 NO] 2H2O (0, 200 and 300µM), sodium ferrocyanide Na4Fe (CN) 6 ( 300, 100 and 0 µM) respectively and deionized water (control), sown in buckets with 15 kg of soil incubated for 50 days containing copper concentrations CuSO4.5H2O (0, 60 and 200 mg kg-1). The design consisted of randomized blocks with 12 treatments and 4 repetitions, making a total of 48 plants. in ecophysiological variables: height, leaf area and number of leaves, stem diameter increased by 32, 66% and 11.29% in the treatments with 60 mg kg-1 of copper and 200 mg kg-1 of copper, respectively. There was no effect of treatments on the chlorophyll content measured by the SPAD index and gas exchange. The chlorophyll a fluorescence variables indicate that the concentration of 200 mg kg-1 of copper caused damage to the structure of the PS II reaction center complexes and indicate a slightly protective effect of nitric oxide-NO present in sodium nitroprusside and cyanide present in sodium ferrocyanide, reflecting a smooth functioning of the maximum activity of photosystem II and the electron transport chain.