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Crescimento foliar e atividades das enzimas antioxidativas em plântulas de girassol suplementadas com percolado de aterro sanitário e submetidas a estresse hídrico RESUMOEm regiões áridas ou semiáridas, a escassez hídrica tem sido um dos principais fatores limitantes da produção agrícola. Diante disso, o presente trabalho objetivou analisar os efeitos da aplicação de percolado de aterro sanitário no crescimento foliar (número de folhas e área foliar) e as atividades das enzimas antioxidativas: superóxido dismutase (SOD), catalase (CAT), peroxidase do ascorbato (APX) e peroxidase do guaiacol (GPX) em folhas e raízes de plântulas de girassol submetidas às condições de estresse hídrico. O delineamento experimental foi o inteiramente casualizado, disposto em arranjo fatorial dois (irrigadas ou não irrigadas) x quatro (areia; areia + adubo orgânico 100 kg N ha -1 ; areia + percolado de aterro sanitário 100 kg N ha -1 ; areia + percolado de aterro sanitário 150 kg N ha -1 ), com cinco repetições. Em relação aos parâmetros foliares, o tratamento 100 kg N ha -1 suplementado com percolado de aterro sanitário obteve os melhores incrementos no número de folhas e área foliar. Além disso, verificaram-se aumentos nas atividades das enzimas antioxidativas em folhas e raízes de plântulas de girassol suplementadas com percolado de aterro sanitário, sendo provável que as reduções dos efeitos deletérios do estresse hídrico nas variáveis foliares dos tratamentos suplementados com percolado de aterro sanitário tenham ocorrido em virtude das maiores atividades das enzimas antioxidativas, especialmente as da CAT nas folhas e GPX nas raízes. Rev. Ambient. Água vol. 12 n.

Many Brazilian reservoirs are intensely submitted to the silting process, particularly the small and medium size ones. The study aimed to examine the feasibility of using silt sediment to grow sunflower plants under conditions of water stress, by evaluating its effects on the relative chlorophyll contents, dry matter and antioxidative enzyme system. The study was conducted under greenhouse conditions at the Instituto Federal do Ceará Campus Maracanaú, Brazil. The sunflower seeds were sown in buckets containing 1) sand; 2) sand + manure/mixed organic fertilizer; 3) sand + 91.8 g of sediment, and 4) sand + 183.6 g of sediment. The sediment was collected from the Tijuquinha reservoir, Northeast of Brazil. The plants were watered daily to 70% field capacity. At 16 days after sowing, irrigation to half of each group of seedlings was suspended. The experimental design was completely randomized in a 2 × 4 factorial with five replicates. The data of each harvest time were analysed by analysis of variance and the means were compared by Tukey's test (P ≤ 0.05). The addition of silt sediment improved the variables (relative chlorophyll content, and shoot and total dry matters) compared to plants grown in substrate containing sand and sand + compost/mixed organic fertilizer, respectively. In general, a greater increase in the variables was observed with the 200% nitrogen recommendation treatment than the other treatments studied. It is possible that the silt sediment from reservoirs can be an alternative to chemical fertilizers for plant cultivation, reducing production costs, providing improvements in the quality of potable water and restoring the storage capacity of surface reservoirs lost by siltation.

Sanitary landfill leachate is one of the major problems arising from disposal of urban waste. Sanitary landfill leachate may, however, have use in agriculture. This study, therefore, aimed to analyze initial plant growth and gas exchange in sunflower seedlings supplemented with sanitary landfill leachate and subjected to drought stress through variables of root fresh mass (RFM), shoot fresh mass (SFM), total fresh mass (TFM), relative chlorophyll content (CL), stomatal conductance (g ), transpiration rate (E), net photosynthetic rate (A), ratio of internal to external CO concentration (Ci/Ca),water use efficiency (EUA), instantaneous carboxylation efficiency (A/Ci), and electron transport rate (ETR). The experimental design was a completely randomized 2 (irrigated and non-irrigated) × 4 (sand, sand + 100 kg N ha organic fertilizer, sand + 100 kg N ha sanitary landfill leachate, and sand + 150 kg N ha sanitary landfill leachate) factorial with five replicates. Under drought stress conditions, leachate treatment supplemented with 100 kg N ha exhibited higher plant fresh weights than those of the treatment containing 150 kg N ha. Increases in fresh mass in plant treatments supplemented with 100 and 150 kg N ha sanitary landfill leachate were related to higher photosynthetic rates.