A. Santi

Aclimatação ao frio e dano por geada em canola

O objetivo deste trabalho foi avaliar a influencia da aclimatacao ao frio sobre o dano causado pela geada em diferentes estadios fenologicos de genotipos de canola. Foram realizados cinco experimentos em ambiente controlado, em 2006, 2007 e 2008. Os fatores avaliados foram: genotipos, aclimatacao (com; sem), intensidades de geada, estadios de desenvolvimento de plantas, regimes de aclimatacao e regimes de geada. As variaveis avaliadas foram: queima de folhas, massa de materia seca, estatura de plantas, duracao de subperiodo, componentes de rendimento e rendimento de graos. A aclimatacao ao frio, antes da geada, resultou em menor queima de folhas e maior massa de materia seca, em comparacao a plantas nao aclimatadas. As geadas foram prejudiciais a partir de -6°C no inicio do ciclo de desenvolvimento, principalmente em plantas nao aclimatadas, e a partir de -4oC na floracao, com reducao do numero de siliquas e do numero de graos por siliqua. A aclimatacao apos as geadas nao contribuiu para a tolerância da canola a esse evento. Geadas consecutivas nao acarretaram maior prejuizo a canola. A aclimatacao de plantas de canola antes da geada reduz os danos, principalmente quando a geada ocorre no inicio do desenvolvimento das plantas.

Filocrono e número de folhas da canola em diferentes condições ambientais

The objective of this work was to determine the number of leaves and phyllochron of canola genotypes, in response to thermal variations associated with sowing dates. Two experiments were conducted in a randomized block design, with a factorial arrangement of genotype by sowing date (5x2, in 2009, and 2x3 in 2010), and four replicates. The number of leaves on the main stem and first branch was determined threefold a week. Phyllochron was estimated by the inverse of the slope between the thermal time and the number of leaves, at the rosette stage and at stem elongation. The number of leaves on the main stem ranged from 11.5 to 16.4; this number was on average 70% lower in the first segment. The number of leaves on the main stem was higher in early sowing, and the opposite occurred in the first segment. The phyllochron was higher in the rosette stage, and values ranged from 21.4 to 52.9 degree-days per leaf, according to genotypes and sowing dates. Late sowing dates increased the phyllochron. Early genotypes have lower number of leaves and phyllochron than medium and late genotypes, and the variability between them increase in late sowings.

Crescimento e acúmulo de biomassa em floresta ombrófila mista no Sul do Brasil

In Rio Grande do Sul State, Brazil, there are few fragments of Araucaria Forest in its natural state, which reinforces the importance of studying these sites in order to understand its dynamics and relationship with the surrounding environment. The aim of this study was to characterize the growth and biomass accumulation of an Araucaria Forest remnant, located in the National Forest of Passo Fundo (FLONA). The experiment was conducted in the municipality of Mato Castelhano, RS, using the method of fixed area. A group of ten plots measuring 30 x 30 m (900 m2), totaling 9,000 m2, installed in October 2009 were used in the study. All trees with diameter at breast height (DBH) greater than 0.1 m were identified. In the years 2009, 2010 and 2012, tagged trees were counted and measured. Biomass vegetation was estimated based on the diameters of the trees. A total of 402 individuals were sampled (447 trees ha-1). The average tree diameter was 0.270 m. The basal area of remaining trees were 35.58, 36.19 and 37.47 m2 ha-1, for the years 2009, 2010 and 2012, respectively. The basal area observed for the period of 2010-2012 corresponded to an increase of 217 % compared to the amount of biomass observed in 2009-2010. The trees in the FLONA of Passo Fundo have increased the diameter over time, resulting in an increase in biomass accumulation.

Dinâmica do pH da água das chuvas em Passo Fundo, RS.

The objective of this work was to evaluate the dynamics of rainfall pH in Passo Fundo, RS, Brazil, from 1992 to 2007. The rainfall pH was monitored in 50 mL samples collected in a 10-cm diameter PVC tube connected to a rain gauge; samples were then stored in a freezer for later determination of pH. The dynamics of rain water pH was evaluated through the annual and monthly averages of the pH, the empirical probability of pH values distributed over the seasons, and the pH accumulated relative frequency. The rainfall events in Passo Fundo region have pH higher than the critical threshold (pH 5.6) to be considered acid rain. The analysis of a 16-year period showed reduction of the rainfall pH at 0.023 per year. Over that period, the average pH fell from 6.1 to 5.8. The rainfalls were slightly more acidic in the summer and spring than in the autumn and winter. In general, the analysis of rainfall events in the region showed no immediate risk of environmental acidification.