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The sensitivity analysis of genetic coefficients used in the productivity simulation of sugarcane by Canegro/DSSAT model (CD) was performed in order to identify which parameters have most relevance in the model calibration. The CD uses 20 parameters that aim to capture the differences between the varieties of sugarcane. The sensitivity analysis has been developed varying one parameter at a time within a certain range and keeping the others constant. Were simulated the stalk dry weight, leaf area index of green leaves and sucrose dry weight at the end of each crop cycle in a period of twenty years, between 1995 and 2014, considering three planting dates, August 01, September 01 and 01 October. The simulations were made to the city of Pelotas - RS and the results were evaluated by the standard deviation (D). The results show that genetic coefficients with great sensitivity in the simulation of the stalk dry weight were PARCEmax (D ≈ 6 t.ha -1 ) and STKPFmax (D ≈ 5 t.ha -1 ). In the sucrose dry weight simulation, the genetic coefficients with higher sensitivity were PARCEmax (D ≈ 3,5 t.ha -1 ) and STKPFmax (D ≈ 3 t.ha -1 ). In the simulation of the maximum leaf area index, the more sensitive genetic coefficients were LFMAX (D ≈ 2 cm 2 .cm -2 ), TT_POPGROWTH (D ≈ 1,4 cm 2 .cm -2 ) and Mxlfarea (D ≈ 1 cm 2 .cm -2 ). The results also show that differences in the planting date have influence in the sensitivity of genetic coefficients.

Mangabeira (Hancornia speciosa Gomes var. gardneri) is one of the most important fruit trees in the cerrado biome, its fruits being highly valued both for in natura consumption and for processing. Although its seeds are delicate, losing viability within a few hours after collection, seeds still represent the predominant tool of propagation multiplication of this species, since the plant encounters limitations in the formation of adventitious roots, hindering vegetative propagation. Thus, the present work aims to evaluate the in vitro establishment of Mangabeira seedlings as a function of the extent of natural desiccation and the sucrose concentration in the culture medium. Four sucrose concentrations (15, 30, 45 and 60 g L-1) and four natural drying periods (24, 48, 96 and 192 h after the seed pulping) were used in a factorial experiment. 60 days after in vitro culturing of the naked embryos, the following variables were evaluated: germination %, germination speed index (GSI), mean germination time (MGT), oxidation index, culture medium contamination index, length of the largest root, stem diameter, seedling height and number of live and dead leaves. The interaction between desiccation times and sucrose concentrations was not significant for any of the variables analyzed. Germination was influenced only by the desiccation time, being reduced after 106 hours of natural drying. Increasing concentrations of sucrose up to 60 g L-1 reduced GSI and seedling height. In contrast, leaf mortality decreased, which contributed to the production of seedlings with greater ability of acclimatization to field conditions. Key words: Germination, in vitro cultivation, desiccation, Hancornia speciosa Gomes.

Rice phenology and development are events controlled by environmental and genetic factors, and the yield potential of the crop is defined by their interaction. This study aimed at analyzing the performance of irrigated rice genotypes in contrasting ecosystems and their effects on morphophysiological characteristics. Two ecosystems (tropical and subtropical) were analyzed, as well as cultivars recommended for tropical (BRS Catiana and BRS Jaçanã) and subtropical (BRS Pampa, BRS 7 Taim and IRGA 424) regions. The experiments were arranged in a complete randomized block design, with four replicates, being the factors the genotypes, sowing times and sites. The phenological development, biomass dynamics, radiation use efficiency and grain yield were evaluated. The accumulated degree-days demand for flowering decreased faster in the tropical ecosystem than in the subtropical ecosystem for late sowing. The radiation use efficiency values were similar in the subtropical ecosystem and yield was high for all sowing dates. On the other hand, the tropical ecosystem showed a high variation for radiation use efficiency values and yield. The higher accumulation of degree-days and solar radiation during the reproductive and grain-filling phases contributed to increase yield in both ecosystems. RESUMO A fenologia e o desenvolvimento da planta de arroz são eventos controlados por condições ambientais e fatores genéticos, sendo o potencial produtivo da cultura definido pela sua interação. Objetivou-se analisar o desempenho de genótipos de arroz irrigado em ecossistemas contrastantes e seus efeitos nas características morfofisiológicas. Dois ecossistemas foram analisados (tropical e subtropical), bem como cultivares recomendadas para regiões tropicais (BRS Catiana e BRS Jaçanã) e subtropicais (BRS Pampa, BRS 7 Taim e IRGA 424). O delineamento foi o de blocos casualizados, com quatros repetições, sendo fatores os genótipos, épocas de semeadura e sítios. Avaliou-se o desenvolvimento fenológico, dinâmica da biomassa, eficiência no uso da radiação e a produtividade de grãos. No ecossistema tropical, a demanda de graus-dia acumulados para o florescimento decresceu com maior magnitude que no subtropical, para as semeaduras tardias. No ecossistema subtropical, os valores de eficiência no uso da radiação foram similares e a produtividade elevada para todas as épocas de semeadura. Já no tropical, verificou-se variação nos valores de eficiência no uso da radiação e produtividade. Maiores acúmulos de graus-dia e de radiação solar na fase reprodutiva e de enchimento de grãos contribuíram para o aumento da produtividade em ambos os ecossistemas.

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