Lettuce has highlight as an important crop for human consumption, to having good flavor and important nutritional characteristics and potassium is one of the main nutrients that crop. This work aimed to evaluate the influence of potassium in morphological and physiological lettuce responses in South of Tocantins State. The experimental design was randomized block in factorial scheme of 4 x 6 with three replications. Four levels were evaluated of K2O: 0; 100; 200 and 300 kg ha-1 in six development stages: 15; 22; 29; 36; 43 and 50 days after emergency. Was determine the specific leaf area, net assimilation rate, relative growth rate and abso-lute growth rate, as well as the leaf, stem and root weight. During the duration of the experiment occurred high temperatures that caused a physiological disorder known as tipburn, which compromises calcium uptake by the plant. The potassium levels did not influence the morphological and physiological responses of lettuce as well did not significant differences among levels for leaf, stem and root weight. The partition of assimilates in the plants was influenced by crop management whit significant variation among evaluation times.

This work aimed to evaluate the influence of the substrate and the level of moisture on the germination of 'pau-de-balsa'. Before installation of the germination test, seeds were immersed in hot water at 80 °C until cooling to overcome dormancy. We evaluated the substrate sand and vermiculite, moistened with water volumes equivalent to 60%, 70%, 80% and 90% of the capacity to retain water. The experimental design used was completely randomized in a 2 x 4 factorial with four replicates of 20 seeds. The effects of treatments were compared for germination percentage, speed index and average time of germination. The seeds had higher germination in sand substrate, and the moisture level of the substrate does not affect the variables analyzed.

This work aimed to study the weed population dynamics of weeds and their influence to analyze in the corn production with the reduction of the space between lines in no-tillage system. The study was conducted in 2003/04 agricultural years, at the Experimental Station of Coimbra ¿ UFV. The experiment was conducted in a complete randomized block design. Treatments were arranged in a 3 x 3 x 2 factorial scheme with four replicates (three cultivars - UFVM 100, AG 9010 and AG 1051) three nitrogen application ways (0, 120 kg ha-1 of N in planting and 30 kg ha-1 at sowing + 90 kg ha-1 at four fully expanded leaves) and two plant spacing (1.0 and 0.5 m). For the phytosociological study, a square of 0.30 m of side was used, thrown at random once in each treatment before the application of the herbicides and 30 and 60 days after the application. The species with the highest density was Artemisia verlotorium, whatever the time of assessment and management used throughout the sampling dates. The population dynamics and the mass accumulation dries of the plants were not influenced by the spacing of the corn, for the nitrogen fertilization and for the studied cultivars. The spacing reduction, from 1.0 m to 0.50 m, provided an increase of 8% in grains productivity.

This study was aimed to adjust probability distributions to a data series of maximum and minimum daily air temperature of Iguatu city in different periods of time, for the purpose of observe that the distributions under study has a better performance and has recommended its use to estimate the probability of occurrence of the estimated values of maximum and minimum air temperature. For the adjustment the data in distribution of frequency were used six probability distributions: Beta, Gamma, I Gumbel, Log-Normal, Normal, and Weibull. Through the adherence tests of Kolmogorov-Smirnov at 20% of significance and Chi-square at 5%, the distributions Normal Log-normal and have a better fit to the data for all scales analyzed, recommended the use of normal function by ease the estimation of its parameters and probabilities.

Bactris gasipaes is an important Amazonian culture as the main source of hearts of palm. Techniques of plant tissue culture are promising tools in breeding programs of this culture. The objective of this study was to develop protocols for the in vitro establishment and callus induction in Bactris gasipaes shoot tips. Shoots were collected from young plantlets of B. gasipaes, which were disinfected with NaOCl 0.63, 1.25 and 1.88% (v/v), for 10, 20 and 30 minutes. After that, shoot tips were removed and inoculated in MS medium with factorial combinations of the growth regulators 2,4-D (0.0; 5.0; 10.0; 20.0 and 40.0 mg.L-1) and BA (0.0; 3.0 and 6.0 mg.L-1). The experimental design was entirely randomized, replicated three times with ten tubes containing one explant per plot. The disinfection was efficient for 20 minutes of immersion in NaOCl 1.25%, which resulted in 90% of explants without contamination and low oxidation. The greater callogenesis percentage was of 60%, reached at 10.0 mg.L-1 2,4-D and 3.0 mg.L-1 BA combination.

Excessive salt can to promote water soil retention, reducing your availability to plants. Besides, they can interfere in protoplasm metabolism. The plants ability to survive in salinity conditions is an important factor to geographic distribution and agriculture in salinized regions. The objective of this work was to verify the effects of the NaCl in the growth, dry matter distribution and N, K, Ca, Mg, Na, and Cl content in young plants. The experiment was conducted in 'Leonard' pots, with nutrient solutions, with NaCl (0, 25, 50 and 100 mmol L-1). Increasing of NaCl concentration reduces growth and total dry matter. There was an increase of N and K content, in shoots, and N and Mg content in roots. There was an reduction in Mg content in shoots, and reduction of Ca content in roots with increasing of NaCl. Leucaena plants were inefficient to exclude Na and Cl, in shoots principally.

Through this research work, evaluating the chemical-bromatologic composition of in natura sugar cane as related to hydrolysis with whitewash. The work was conducted in the Forage Culture Sector of the Animal Science College at José do Rosário Vellano University (UNIFENAS), campus of Alfenas (MG). The experimental design utilized was the completely randomized in a factorial arrangement 4x5, four doses of whitewash were studied (0.0; 0.5; 1.0 and 2.0% on the basis of natural matter) in five times aerobic exposure (0, 6, 12, 24 and 48 hours), with four replicates. The addition of whitewash to sugar cane promoted lower temperatures till 12 hours of storage, from this point on, there no further effects of whitewash upon temperature control. The content of dry matter and ashes increased linearly with addition of whitewash, while protein content decreased. Whitewash promote no fall in the contents of water-neutral detergent-insoluble fiber and lignin, nevertheless, the contents of acid detergent insoluble fiber decreased, with more forceful when using 0.5 and 2.0% of whitewash. The use of whitewash in the hydrolysis of sugar cane alters the chemical bromatologic composition, however, the use of this additive is unjustified, because is not effect positive on the fiber content. The sugar cane in natura and hydrolyzed present the best composition immediately after the desintegration.

Liming is an alternative to correct the consolidated surface acidity and gypsum allows the supply of calcium and reduction of aluminum saturation in subsurface layers of soils in Brazilian Cerrado. The objective of this study was to evaluate the correction of acidity of ground the effects of superficial liming and gypsum on Ultisol cultivate. The experiment was carried out at the greenhouse of Soil Laboratory, at Federal University of Tocantins (Brazil) to evaluate of application of limestone and gypsum, during three periods of collection (30, 90, and 150 days after correction) and three depths of collection (0-5, 5-10 and 10-15 cm) in Ultisol of Tocantins State (factorial 2x3x3), with four repetitions. After the collections had been analyzed the soil chemical properties (pH, K, Here, Mg, H, Al, CTC, and V%). The surface applied lime was effective in neutralizing soil acidity, at a depth proportional the time. The application of gypsum improved the ground in depth, increasing the Ca, beyond diminishing aluminum.

In Northeastern Brazil peanut is an important culture due to its high palatability, nutritional value, grain high oil content and for being an additional and/or alternative source of income for small regional farmers. However, production is insufficient, primarily due to low yield, lack of use of adequate cultivars and inadequate management. Therefore, an experiment was carried out (March/June, 2008), at the Universidade Federal Rural do Semi-Árido (UFERSA) (Semi-arid Rural Federal University), in Mossoró, RN (Rio Grande do Norte State, Brazil) experimental station, to evaluate yield of 2 creeping peanut cultivars (Runner IAC 886 and IAC-Caiapó), grown in 2 row spacings (0.5 m and 0.9 m). In a complete randomized block design treatments were allocated in a 2 x 2 factorial (2 cultivars x 2 row spacings), with 4 replications. Production components and yield were evaluated (number pods plant-1, number seeds meadow-1, 100 seed weight, pod yield, percentage yield almonds and straw yield). Cv. Runner IAC 886 showed higher yield than cv Caiapó, in both row spacings (0.5 m = 5,169 kg ha-1 and 0.9 m = 4,264 kg ha-1) mainly due to the number of pods plant-1. Row spacings affected both cultivars. Runner IAC 886 showed higher yield of pods at the 0.5 m spacing (5,897 kg ha-1) and Caiapó in the 0.9 m spacing (4,264 kg ha-1). Straw yield was higher in the lower row spacing cultivation.

This work aimed to evaluate the effect of cut height on jurema-preta control. Thus, two trials were carried out, one in September 15th and other in December 15th of 1997. The experimental area had 1,400 m². Treatments were the height cuts of 25; 50; 75 and 100 cm from the soil. Evaluations were done when more than half of plants were showing 50% of their regrowth with a diameter of 0.7 cm. The experimental design was in randomized blocks with split-plot, being the height cut the parcel and the cut the sub-parcel. In the first trial and at the end of the 3rd cut, the higher mortality of 84.6% was found among plants cut at 75 cm and the higher number of regrowth was observed in plants cut at 100 cm, but the stem diameter was not affected by treatments. In the second trial and at the end of the 3rd cut, the higher mortality of 50% was found among plants cut at 100 cm and the other variables were not affected by cut height. The control of jurema-preta may be done in September, cutting the plants at 75 or 100 cm from the soil and always cutting the regrowth plants when they reach 0.7 cm of diameter. The jurema-preta control by standardization cut in December was inefficient regardless the cut height.