Eduardo Venske

Efeito do nitrogênio suplementar sobre os componentes de rendimento da soja em condição de estresse hídrico

Nitrogen is the nutrient required in the largest amounts by soybean. Its limitation to the plants can compromise the final yield of the crop. The aim of this study was to evaluate the effect of additional nitrogen on soybean yield components through the use of different sources, doses and times of application. The study was carried out in a crop area in Arroio Grande, RS. The reproductive stages in which the nitrogen was applied were: R1; R3; R5.1; R5.2; R5.3; R5.4; R5.5; R6 and R7, via ammonium nitrate and amidic sources, in the following doses: 0, 30, 60, 90 and 120 kg ha-1. The variables evaluated were: number of pods, number of grains per pod and thousand grain weight of the lower, middle and upper thirds separately and total, as well as yield. Randomized blocks were performed with three replicates. Data were subjected to variance analysis and regression analysis was applied. The variables that did not show interaction with doses were analyzed by the Tukeys multiple comparison test, at 5% probability. The application of nitrogen in the soybean reproductive stages positively influenced some yield components. However, it did not increase the yield, possibly due to water stress to which the crop was subjected.

Initial development of red and cultivated rice in response to light and air temperature

ABSTRACT - Light is an important factor in the cold protection process in plants. The objective of this study was to evaluate the relationship between temperatures and levels of quantity and quality of light on the initial development of rice cultivars and red rice biotypes. Two experiments were conducted, in the laboratory and in the greenhouse, from July to November 2012. The factors studied in experiment I were: temperatures (25 oC and 18/13 oC); cultivars/biotypes (IRGA 424 and PUITA INTA-CL/AV 6716 and AV 6722) and light (white, blue, green, yellow and red, 86% and 93% shading and dark). In the second experiment, the factors were seasons (August and November); cultivars/biotypes (IRGA 424 and PUITA INTA-CL/AV 6716 and AV 6722) and light (white with cover, white, blue, green, yellow and red, 86% and 93% shading). Were evaluated normal seedlings, shoot and root length, shoot and root dry weight and leaf area. The cultivars and biotypes studied have a similar behavior in response to temperature and light during early development. Light, especially the red wavelength, has increased cold tolerance in rice.Index terms: environmental stress, germination, emergency, seedling.

Relative expression of CYP and Arabinogalactan genes in soybean seed coats

The aim of this study was to evaluate the relative expression of two candidate genes, CYP (cyclophilin) and Arabinogalactan, possibly involved with seed quality, in contrasting soybean seed coats. The following genotypes were used: BMX Potencia RR and CD 202, both with yellow coats, and TP and IAC, with black coats. The relative expression of the genes was evaluated by qPCR in seven development phases of the coats of the four genotypes at 25; 30; 35; 40; 45; 50 and 55 days after anthesis. The design was completely randomized, with three replicates. The data were submitted to analysis of variance and the means were compared via the Scott Knott test, at 5% probability. The CYP gene showed greater expression in the intermediate stages of development of the coats of the genotypes CD 202 and IAC, yellow coat and black coat, respectively. The A rabinogalactan gene presented greater expression in the final stages of coats development of BMX Potencia RR.

Seletividade de herbicidas sobre arroz irrigado em resposta à época de semeadura e redução da luminosidade em fases do desenvolvimento

Different environmental factors can have effect on the selectivity of herbicides on crops. The aim of this experiment was to evaluate the effect of sowing time and of artificial reduction of the luminosity at different stages of plant development on the herbicide selectivity and yield components of irrigated rice. The field experiment was carried out in 2012/2013 harvest, with the IRGA 424 cultivar. The factors studied were: sowing time (October 18 and November 9), herbicides (weeded control, bispyribac-sodium and penoxsulam) and stages of development of culture with luminosity reduced by 70% [control, seedling (S0-V4), vegetative and reproductive periods and entire cycle]. The experimental design was the completely randomized, in a factorial scheme, with four replications, but sowing time and reduced luminosity were imposed in strips, to make possible the experiment. Evaluated: visual phytotoxicity, stems and panicles per area, spikelets per panicle, spikelet sterility, thousand seed weight and yield. Data were subjected to analysis of variance by F test (p ≤ 0.05) and mean test of DMS Fischer (p ≤ 0.05). The sowing time influences the selectivity of bispyribac-sodium, and when held near the beginning of the period recommended, in October 18, reduces the yield of the cultivar studied. The artificial reduction of light in different phases of the development does not affect the selectivity of herbicides bispyribac-sodium and penoxsulam on irrigated rice.

Abiotic factors in the effect of herbicides on the physiological quality of rice seeds

The aim of this study was to evaluate the physiological quality of rice seeds with the application of herbicides in two sowing seasons, and for the artificial reduction of lighting at different stages of crop development. The field experiment, carried out in the 2012/2013 crop year, consisted of a 2x3x5 factorial, comprising the factors: sowing season (18/10 and 09/11); herbicide (control (weeding), bispyribac-sodium and penoxsulam); and crop development phase under light reduction (control; seedling stage, vegetative phase, reproductive phase and the entire cycle). The cultivar used was IRGA 424. The following were evaluated in the laboratory: thousand-seed weight, germination, first germination count, cold test, electrical conductivity and the length and weight of seedling shoot and root dry matter. Late sowing results in the production of rice seeds of lower weight and physiological quality. The application of sodium- bispyribac on the rice that was sown later, leads to a reduction in the vigour of the produced seeds. With reductions in artificial lighting during the vegetative phase, rice seeds with greater mass and physiological quality are obtained, whereas when the lighting is a reduced for the entire crop cycle, poor quality seeds are produced.